Chapter One - Photovoltaics

The process of converting light into electricity was perfected as a product of the space industry. Satellites needed a source of power while in orbit or traveling among the planets, and the logical solution was to deploy large panels of photovoltaic modules. Toady, this technology is available to ordinary citizens of Earth to provide clean, renewable energy for everyday use.

Terrestrial use of PV's is becoming quite popular in the recreational vehicle industry, as PV power frees RV'ers from the use of noisy and polluting gasoline generators. Our discussions will be directed at those of you who dwell in a house bus or truck, but is applicable to all forms of habitation.

Most commercially available PV modules are composed of 36 series-connected PV cells wired internally to provide 12 volt DC electric power. Modules are rated in Watts, which is a product of the module's operating voltage multiplied by the output current. 12 volts times 4 amps = 48 watts, etc. This will allow the user to specify modules of a size and quantity to satisfy expected power requirements of the home power system. It also allows the user to have a benchmark by which to measure the panels performance against itself and others of similar output.

Multiple modules can be wired in series to increase voltage, parallel to increase current, or series and parallel to increase both. It is possible to construct very large arrays of modules, capable of outputting a virtually unlimited amount of power.

Orientation of the modules to the sun is critical to the successful operation of a PV system. Ideally, the modules will be at a 90° angle to the sun's rays at all times. In practice, this is not always practical. Tracking mounts are available which will automatically reposition the modules continuously throughout the day, although they are quite expensive, and installed only on large arrays. Most systems are installed on a fixed-azimuth mount, which is adjustable seasonally for elevation. This means that the modules are pointed due south (Northern Hemisphere) or north (Southern Hemisphere), and the angle to the horizon adjusted several times a year as needed to keep the modules best aligned with the sun's rays. The result is slightly lower output power during the morning and evening, but results also in a much lower installed price. Even small areas of shade on a module will decrease the output dramatically, so location is an important consideration during installation.

PV modules, once installed, require no maintenance whatsoever, except for occasional cleaning to remove dust, bird droppings, etc.

The real beauty of PV's is that it is possible to add modules to a system at any time without compromising the efficiency of either the existing system, or of the new modules. Panels do not have to be of the same manufacturer, wattage or even construction type, as long as the voltage of each module matches the others. This allows one to begin constructing a solar power system with a very small panel and add to it as finances allow, with no penalty.

If powering your home with solar power appeals to you, I urge you to investigate purchasing a small photovoltaic panel and power even one small lamp with it. Solar powered radios and flashlights are available and are great tools for learning more about this exciting and non-polluting power source.

Chapter Two - Batteries

Regardless of where the electricity you use comes from in your buses' electrical system, It must be stored in batteries in order to be used when you are not connected to the electrical power grid or running a generator. This installment will help you select a battery system that best suits your needs and provides the best value in terms of longevity and cost.

Batteries come in a wide variety of types, some of which are better suited to the service required in domestic use than others. The most common types you might encounter are described as follows:

• Automotive Batteries: Engine starting batteries are by far the most familiar to people, but are the least suitable for powering household loads. These batteries are designed to provide high current (up to several hundred amps) for only a few seconds, and then be immediately recharged by the vehicle's alternator. They do not stand up well to the deep discharges that a renewable energy system requires, usually failing after only 50-100 discharge cycles.

• Marine/RV Batteries: These cells are an improvement over engine batteries, as they handle deeper discharges and repeated cycling better, lasting 400-600 cycles. They are commonly available as 12 volt, group 24 or 27, with capacities in the 50-65 ampere-hour range. Their smaller size makes them an attractive choice where space is limited.

• Traction Batteries: Specifically designed for heavy duty deep-discharge service, these batteries are frequently called "golf cart batteries" and are used in a variety of applications, including cordless floor polishers, lift trucks, electric vehicles for street use, etc. Their thick plates and internal chemistry allow them to be drained repeatedly to an 80% depth of discharge and then fast-charged, with an estimated life expectancy of 500-1,000 cycles or more. They are commonly available in 6 and 8 volt configurations, in capacities of 180-245 ampere-hours. These batteries are currently the best choice for any renewable energy system, given a reasonable budget.

• Gel Cells: Also known as sealed batteries or Absorbed Glass Mat (AGM), these cells use an electrolyte which has been compounded to have a heavy, paste-like consistency. There are no vent caps, and no way in which to add to or inspect the electrolyte level. As such, they can be operated in any position, including inverted, with no ill effects. They are generally quite good at deep-discharge, and can take fairly quick recharges. Disadvantages include high cost of purchase and strict charging current and voltage regulation.

• Telephone Batteries: A specialized battery of lead-calcium construction. Not very good for deep-discharge, but often available free or at low cost when a PBX system is removed or replaced. Generally these cells have a slightly lower terminal voltage than normal lead acid batteries. The calcium impregnated in the plates helps limit the production of hydrogen during recharging and helps minimize self-discharge during periods of inactivity.

• Nickel-Cadmium: Absolute top-notch battery technology! Can not be damaged by over discharge, misuse, freezing, boiling, left lying about dead, or any other abuse. Quite expensive to purchase new, but will be the final battery you will need to buy in your lifetime. Requires 10 cells to make 12 volts, and has a higher fully-charged voltage, which make it incompatible with some charging systems. If you are ever offered some of these used, snap them up, no matter how bad they may look, for they can be reconditioned to as-new at only a small price. Virtually unlimited life cycle, given reconditioning when needed (about every ten years).

• Nickel-Iron: Also known as Edison cells. Every bit as good as Nickel-Cadmium. Often used in railroad signaling devices, can be reconditioned easily. Capacity is slightly lower per Kg of weight than NiCad.

• Exotic battery technologies:Nickel-metal-hydride, Fuel cells, Lithium-ion, Sodium sulfur, etc. Obviously, if you or I could afford any of these types of batteries, we wouldn't be driving around in converted trucks or buses, would we?

It is considered essential that all of the cells in a battery, or batteries in a multiple battery system are of the same age, type, capacity, and condition and are exposed to similar conditions of charge, discharge, temperature and maintenance. Mixing and matching battery types or adding new batteries to a bank of older cells is a sure way to be disappointed in your power system.

Chapter Three - Charging Batteries

Last issue, we explored the various types of batteries that you might encounter for powering the lights and other loads on your house bus or truck, or in a stationary renewable energy system. In this article, the wonders of charging those batteries will be presented.

I frequently tell people that batteries are a kind of life form, an electrical pet which requires husbandry to keep happy. They don't mind equitable work, and it is their pleasure to serve you for many years. Forget to feed or water them, freeze or roast them, neglect and mistreat them and they will crawl into a corner to shrivel up and die.

This writing is about the feeding part.

Your batteries should be recharged as soon as possible after use. Although they will continue to provide power until their capacity is reached, best battery life expectancy is realized by immediate and full recharging.

Several methods of charging are common: from the power grid, solar (and other renewable sources) and the engine in your vehicle.

Grid powered chargers are available in many configurations and ampacities, and may include manual or automatic controls for current, voltage and possibly may include multiple stage charging.

Solar charge controllers are likewise available in a multitude of types. Properly installed, they will maintain your batteries at full capacity when sufficient sun is available.

Charging from a vehicle's generator or alternator is the trickiest of all, as you will see in a future article

Multiple stage charging is the best and most economical way to fill up batteries. Three stages are usually preferred, bulk, absorption, and float.

Bulk charging is done to return 75% of the energy removed from the battery quickly. Amperage is kept as high as the battery and charging source will allow, usually equal to a value of 10-20% of the batteries ampere-hour capacity ( a 220 ampere-hour battery would be charged at 22 to 44 amps, expressed as C10 or C5. The equation for determining this value is Capacity divided by charging current determines time to charge fully [C value] 220/5=44=C5) When the battery voltage reaches approximately 2.41 volts per cell (14.5 volts for a 12 volt battery), absorption stage is initiated.

In absorption stage, the current into the battery is limited to hold the terminal voltage at a pre-set value just below it's gassing voltage, usually 14.5-14.6 volts, for a specified period of time, from half an hour to several hours, depending on the specifications of the battery manufacturer. During this time, the battery is allowed to slowly absorb approximately 20% of the electricity being returned in the charging process. At the end of the given time, the float stage is initiated.

Float charging is a condition in which the battery is held at a specified voltage that is well below it's gassing point, but high enough that the remaining 5% of capacity can be returned. Typical float voltage for a 12 volt lead acid battery might be 13.1 volts. A battery can be left on float charge indefinitely without damage or excessive water loss.

Then there is the issue of occasional over-charging of deep cycle batteries, which is required for good battery health. This is also called an "equalizing charge", and it is applied once a month or so to help even out the state of charge between all of the series-connected cells in a battery. The regulator or charge controller is set to allow the battery's terminal voltage to reach 15+ volts for a period of several hours. This will cause furious gas production in the cells, helping to strip away any soft sulfate deposits, and de-stratifying the electrolyte. Care must be taken to allow the pressure inside the cells to dissipate, usually by removing the cell caps. This generally leads to electrolyte being spattered onto the top of the battery, which must be cleaned up after the equalizing process. The hydrogen gas produced is highly explosive, and all care should be taken to prevent it's being ignited.

The state of charge of any lead-acid battery can be determined by the use of a battery hydrometer, which indicates the specific gravity of each cell in a battery bank. Personally, I prefer modern digital electronic instruments to mucking about with corrosive acids. When the batteries are operating properly, the readouts from the instruments is more than adequate to indicate the state of charge. I save the hydrometer reading for once-or-twice a year maintenance and for locating a sagging cell when performance drops off due to age.

Chapter Four - Loads, Part One

Now that we have a battery and a way to charge it up, it's time to begin thinking about how we will consume the power stored in it. "Why do I need to read an article on how to make a battery dead?" you ask. Simple, it's difficult to consume battery power efficiently. In order to make the simple yet more complicated, we'll break down the various loads into categories. This issue, the subject is lighting.

Probably the most important contribution to comfort in your house truck or bus a power system can make is to replace the use of candles or lanterns. Several different types of lighting appliances are available, and you may decide to choose to use a mixture of types depending of your individual application. Briefly, here are the most commonly available types.

• Incandescent: The most familiar type of light, the common light bulb. While they are inexpensive and readily available, they rate at the bottom of the efficiency chart, as only 10% of the power fed to them emerges as light, the rest is wasted as heat. Incandescent lamps can be installed in ordinary household fixtures, in which case standard line voltage lamps can be run from an inverter or shore power, or 12 volt medium-base bulbs can be used and powered directly from the batteries. Low voltage installations can also use automotive tail and marker lamps which are installed in special recreational vehicle (RV) fixtures. Incandescent lamps are a good choice for general lighting where ample power is available and efficiency is not a big factor.

• Halogen: These lamps use a tungsten element immersed in halogen gas, enclosed in a quartz envelope. They are slightly more efficient than incandescent lights, and provide an intense, very white light. Nearly all halogen lamps will be of the low voltage variety, most commonly those used in track lighting. They operate at a very high temperature and require special fixtures to mount the lamp, focus the light, and endure the heat. These lights are very good for areas which require intense lighting, but beware, they tend to cast harsh shadows and would never be considered "mood lighting". Replacement lamps are fairly costly, and they do not tend to last an unusually long time.

• Florescent: We're not talking here about the familiar core-coil ballasted, long tube florescent lights you see on the ceiling of the super market. Florescent lighting has come a long way from the blue-green nightmares that made food turn a disgusting color right before your eyes. Modern fluorescents are now electronically ballasted and are color corrected to resemble sunlight in a most pleasing manner. These lamps put out four times more light per watt consumed than incandescents and operate cooler as well. The popularity of compact florescent lights grows daily. These lamps can be installed in standard medium-base fixtures and come in a variety of wattages (remember, a 25 watt CF will put out the light of a 100 watt incandescent). They are also available in low voltage electronically ballasted models as well. Use florescent lighting anywhere that a good quantity of light is needed for a prolonged period (their life is shortened by turning on-and-off frequently). These lamps are somewhat expensive, but will last ten times longer than standard bulbs, and are very well suited for use on a battery powered-system.

• LEDs: Light Emitting Diode lighting for general illumination is still in it's infancy, but these solid-state devices promise to revolutionize that way we light our homes. Virtually 100% efficient, this technology will become more prevalent as the cost of white LED's drops and newer designs become available (remember, you read it here first). At this point, if you want to experiment with LED lighting, you can buy an LED flashlight, or small lamps which will install in a low voltage fixture and illuminate a small area.

As you can see, many options present themselves when choosing lighting for your home. You might decide to put a compact florescent light in your kitchen and living room fixtures, a halogen bulb for your reading lamp and an incandescent in a closet where it will be used infrequently and only for a few minutes at a time. If you are on the road a lot and your engine keeps the batteries full a good bit, why bother with efficiency? If you find yourself with barely enough power to keep the light above your desk running in the middle of winter, you'll want to investigate the most efficient lighting available. Most of us fall somewhere in between, and with careful consideration, there will be power enough for all.

Chapter Five - Loads, Part Two

Last episode, we explored the various methods of abusing electrons in the pursuit of making light. While there is no limit to the ways of consuming power, it is helpful to have some idea of which loads will drain our batteries fastest, which will draw a small amount of current over a long period of time, and which are completely inappropriate for use in a Renewable Energy system.

Some appliances consume large amounts of power, but are used only for a few minutes at a time, perhaps only once a day. A hair dryer, water pump, or microwave oven are good examples. Other loads may draw only a small amount of power, but are used over the course of many hours, or are left powered up continuously. For example, a cellular telephone may be left on all day and turned off at night. Since the current draw is very small when the phone is not being used to make a call, only a small total drain is presented to the batteries. Another example would be a digital battery system monitor, using an LED display which runs 24 hours a day.

Still other devices may draw a considerable amount of power, and be needed for extended periods. The circulating fan in an RV-type LPG-fired furnace, or a full-sized personal computer with a CRT monitor are possible in live-aboard vehicles.

Whatever the loads combinations, it is essential to calculate carefully to avoid constructing a system that is too small to successfully power all necessary appliances and devices. The nuts and bolts of these calculations is not difficult, but beyond the scope of this article. This is where you are best off finding someone who has installed renewable energy power systems to assist in your system's design. It is also possible to learn to design your own system, many books have been written, and a wealth of information is available from Home Power magazine.

Now, about things you are NOT going to be able to use on a battery-powered system. Forget about air conditioning, electric space heaters, most forms of conventional refrigeration, electric cook stoves and water heaters. Unless you have a very sizeable battery system with adequate charging sources, you may find it difficult to use appliances such as waffle irons, crock pots, toasters and toaster ovens, etc. Blenders, vacuums, coffee grinders (!!!) and mixers all are possible in your bus or truck, as are radios, CD players, tape machines and television/VCR's. While most stationary tools such as table and radial-arm saws, planers, air compressors and the like draw too much current for the average vehicle-sized system, most powered hand tools can be utilized, including drills, circular saws, grinders and sanders, electronic soldering tools, etc. AC powered welders are out of the question, but it is quite possible to weld directly from a battery bank, using the proper conditioning and control equipment.

A good use of your renewable energy power system is to recharge small batteries like the ones in cordless tools, radios, flashlights and the like. It is not practical, nor is it desirable to recharge large storage cells such as vehicle starting batteries from your system. These batteries should be recharged from another source, possibly the same one which charges your 'house' system, although through alternate wiring and controls, so as to protect the house batteries from discharge.

A few words about "phantom loads", devices which continue to draw current while giving the appearance of being turned off. In all cases, these must be detected and accounted for. Any device that uses a "wall cube" power supply, or has a display or indicator which remains on after the switch has been cut off will slowly drain the batteries while producing no usable work. Such appliances will require an external on-off switch to completely remove all power when they are not being used. Similarly, electric clocks, VCR's, many consumer radios, and a good few laptop computers will fall into this category. Unplug them completely, or put them on a 'plug strip' outlet bar to allow you to turn them off for real when you are done using them.

Many of you will note that quite a few of the loads mentioned are conventional utility grid powered devices, which brings us to next issue's subject, inverters. Changing low-voltage DC battery power to utility line-level AC power needn't be expensive or difficult, and can make living with renewable energy much more enjoyable and convenient.

Chapter Six - Inverters

The ability to operate power tools and appliances from household power can make life aboard a house truck or bus more pleasant, and allow you to accomplish tasks that would otherwise be impossible while traveling. An inverter is an electronic device which converts direct current battery power into alternating current very like that which flows from utility grid outlets.

Modern inverter technology is durable, efficient, and relatively inexpensive. Choosing the correct inverter for your requirements will help insure that you are getting the best value and satisfying your needs. Inverters are available in many output power ranges, with a variety of options, and are manufactured in several distinct types.

Selecting your battery voltage is the first step in choosing an inverter. Most installations will use 12 volt battery power, although inverters over 2,000 watts will benefit from a higher input voltage, perhaps 24 volts.

The output voltage and frequency of the inverter should match that of the appliances you intend to operate on it. In the US, this is 120 vac/ 60 Hz (Hertz). Nearly all manufacturers offer European specifications of 240 vac/ 50 Hz, and custom voltage and frequency inverters are often available by special order.

Specifying wattage can be a bit tricky. Buying the largest inverter you can afford might seem the best track, but remember that a large inverter running only a small load will consume a disproportionate amount of power from the batteries due to poor efficiency at low output. The same inverter may have better efficiency when operated between 25 and 75% of it's rated output.

Nearly all inverters will power a load larger than their rated output for a reduced period of time. The components and construction are such that the inverter must handle overloads as a matter of starting motors, etc. This may allow a 600 watt inverter to run a 1,000 watt load for several minutes without damage. The continuous-duty rating of the inverter remains 600 watts, but the surge rating might be 1,000 watts for 5 minutes. It is important to inquire about these ratings when purchasing an inverter, as you may find that you need only buy a smaller inverter for your daily usage, and that the surge rating will take care of occasional overloads due to unusual circumstances.

Two varieties of inverter output wave form are currently available, modified-square wave (sometimes called modified sine-wave), and true sine wave. True sine wave inverters produce power that is exactly like utility grid supplied power. They are superlative for powering all types of loads, and may be necessary on sensitive electronic instruments. Efficiencies of sine wave inverters are slightly less overall than modified square-wave.

Modified square-wave inverters (MSW for short) approximate the wave form of utility grid power, and the better ones use circuitry to adjust the wave form to best power the load at hand. The advantage of MSW inverters is that they are relatively inexpensive and quite easy to acquire. There can be serious disadvantages though. MSW inverters aren't a good choice for running induction (capacitor-start) motors, and some cordless tool battery charger systems malfunction and burn up when fed MSW. Additionally, MSW inverters are electrically "noisy" and induce "hash" or interference into audio equipment such as telephones and stereos. Having said this, I must be quick to say that I have both types of inverters in my system, and I find the MSW inverter's performance quite satisfactory. Just be aware of the issues at hand when purchasing.

As for options, most inverters these days will include a 'stand-by' option, which switches any loads that are connected over to the grid when utility power is available. Nearly every type of inverter these days has a 'sleep' feature, which turns the inverter's circuitry off when no appliance is being used, and then automatically turns the inverter on when a power demand is sensed. This saves quite a lot of power over running the inverter full time, and saves the user from having to manually turn the inverter on and off to operate loads from it. Built-in battery chargers, some which are quite sophisticated, are commonly standard equipment on inverters. Low battery cut-out, short circuit protection, thermal cut out, over current protection and other safeguards should also be standard on any inverter you seriously consider.

Some of the more expensive inverters use internal microprocessors to allow user-defined parameters to be set, and sine-wave inverters may have the option of back feeding the utility grid with excess power from your generating sources. This is called utility inertie.

Some inverters have communications ports which allow them to be controlled by and send data to a personal computer. Many manufacturers also offer digital metering systems which can be integrated into the setup to give readings and control the system remotely.

Even an inexpensive inverter the size of a box of kitchen matches can prove itself to be quite useful on the road. Be sure to include a place for an inverter of some description in the plans for your housetruck's electrical system.

Chapter Seven - Power Converters

Before we move on to other enjoyable subjects, there is another type of power processing equipment to consider, Converters. These devices convert utility grid power into 12 volt direct current to run lights and appliances in your bus or truck. "Wait a minute" I hear you say "Isn't that backwards? Just last issue you were telling us all about the wonders of inverters, which change 12 volts DC into household utility power!". This is true, but there are times when you may want to run your low voltage loads directly off of the utility power when it is available, and not drain your batteries. A converter is the way to do this.

Most converters are essentially heavy-duty transformers and rectifiers, not unlike a common battery charger. In fact most converters also charge the battery while they are powering the vehicle's loads. The difference is that converters, unlike chargers, have an internal relay which disconnects the lights and other loads from the house batteries so that the converter takes the entire load itself, allowing the batteries to experience only the charge current.

To be effective, a converter must be capable of supporting a load of 30-40 amperes, while simultaneously supplying a charge current to the batteries of 10 or more amps. In practical terms, this means that the converter must contain a large and heavy transformer. An appreciable quantity of heat can also be expected to be generated, so converters should be mounted where they can receive a free flow of cooling air. It is not unusual for an operating converter to make an audible humming noise, and I have heard some that were positively loud, so take care to install such a device where you won't be bothered by the sound it makes.

The relay inside the converter is a single-pole-double-throw device, which allows the batteries to power the loads when utility power is not being used, and automatically switches the loads over to the transformer when the grid is available.

Keep in mind that most converters supply voltage and current that is neither filtered, nor regulated. Sensitive electronic devices such as audio equipment, two-way radios, cell phones and the like should not be powered from converter power, and instead should be connected in such a manner to assure that they receive only battery power. A dedicated regulated and filtered power supply can be installed to run these devices from the utility power if desired.

The benefits of using a converter are realized when one is switching between utility power and battery power frequently. Many converted buses and trucks have lighting fixtures which can be powered by either type of current, and the bulbs are changed to whichever voltage is being used at the time. Other conversions have light fixtures which contain two lamps each, low and line voltage. Use of a converter allows the use of low voltage lamps in every fixture, simplifying installation and operation of the same. Of course, if you have switched over to using compact florescent lamps, this argument is invalid. Other significant loads such as pumps, fans, and motorized devices are easily energized by use of a converter.

A sufficiently strong battery charger, whether part of an inverter, or as a separate device, can take the place of a dedicated converter in your electrical system. There is nothing particularly complicated about a basic converter, and someone with a working knowledge of electronic principles should be able to construct their own from discrete components.

Chapter Eight - Shore Power

Even if you have installed an effective renewable power system on your bus or truck, there will be times when you will want to connect to utility power when it is available to conserve battery power or run appliances which draw too much current for your batteries to support. The nautical term for this connection is 'Shore Power'. Utility power will allow you to operate space and water heating appliances, recharge your batteries if needed, and live life in the 'normal' consumptive manner.

While connecting to a convenient electrical power receptacle seems simple enough, be sure that you plan ahead for this in the design and construction of the electrical system on your rolling home. Your AC power system can be as simple as several 'plug strips' connected to an extension cord, or be a complex multi-branch circuit load center with circuit breakers for individual appliances. In any event, you will want your installed system to be safe, and conform to any applicable electrical building codes you may encounter.

Foremost in your consideration should be making sure that the frame of the vehicle, and all exposed metal parts, etc are properly grounded while the AC power is connected. Any fault current that finds it's way to the vehicle's frame, by whatever path, will turn the entire metal structure of your truck or bus into an electrocution hazard. Normally, this grounding connection is accomplished by the grounding conductor integral to the connector and cord that connects the system to the utility grid power. Be sure that this part of the circuit is installed properly and is in working order before connecting to any utility power source! Also confirm that the grounding conductor of the receptacle that you are connecting to is properly grounded. A variety of inexpensive indicating instruments are available that can identify faulty wiring or connections, and you should invest in one and use it before connecting your valuable mobile habitation to an unfamiliar power source.

Also very important is the installation of appropriately-sized fuses or circuit breaker devices. These over-current protection devices will prevent your system from overloading the wiring supplying the utility power to your vehicle, and protect your equipment from short-circuit currents. Additionally, you will find it easier to reset an over-current device that trips inside your bus after an accidental overload, than to try to find and access the protective device at the supply end, which may be enclosed inside a locked circuit breaker panel, or be difficult to locate in an unfamiliar (and possibly now very dark) building. It's also good politics to not blow your host's fuses!

If your housetruck includes an inverter or generator, you will need a method of switching between on-board power and shore power. This can be as simple as having the cordset which powers the system plug into the generator, inverter, or utility outlet, as needed. Any manner of transfer switching devices can be installed to make the connection either manually or automatically. It is essential that the inverter and/or generator not be "back-fed" utility power into their output terminals, so be sure that your vehicle's power system is wired properly to prevent this when using shore power.

It is sometimes helpful to have an AC voltmeter which can be used to read the utility power's voltage before connecting, particularly if you may encounter non-standard voltages or receptacle configurations. Finding out too late that you connected your 120 volt system to a 240 volt outlet is sure to be more than mildly disappointing, and possibly very exciting as well

Finally, be sure that any receptacle that you connect to is capable of supplying an adequate amount of current, equal to, or exceeding what your vehicle's system will consume. Also make sure that your cordset, or any extension cords you use to connect are of a sufficiently heavy gauge to carry the expected current.

Of course, it goes without saying that you will be careful when using all forms of electrical power, and observe all prudent and proper precautions, leading to personal and property safety.

Chapter Nine - DC Overload Protection

Recently, a message from one member of an e-mail list to which I belong described an incident where a loose car battery shorted out in the back of her bus and set the woodwork afire. Due to the watchfulness of a policeman and the efforts of the fire fighters, her bus suffered only minor damage. The lesson we can all learn is to plan for the best but protect against the worst.

Batteries in all forms can produce an astounding amount of power when short-circuited. Because the electric current from a battery is Direct Current, special precautions should be taken when installing proper fuses, circuit breakers and disconnects. The renewable energy power system in your bus or truck should have over current protection for the battery itself, as well as each branch circuit.

Any device that is meant to interrupt DC current must be specifically designed for that purpose. Household fuses and circuit breakers are meant to protect Alternating Current voltages and currents, and will not properly protect a battery powered circuit. Additionally, because batteries can supply such a large amount of fault current, these devices must be capable of not only protecting the circuit, but must also be able to do so without becoming a fire hazard themselves.

When a high-current DC fault is interrupted, a sustained, very hot arc can be formed inside the fuse or circuit breaker. This arc is functionally identical to an arc welder discharge, and can produce temperatures well in excess of that required to melt glass, thin metals, and plastic insulating materials. Obviously, combustible materials nearby are at risk, and since the arc allows high current to continue flowing in the faulted circuit, all of the wiring and other devices in the circuit are at risk as well.

DC rated fuses usually have plastic beads inside the body of the fuse. When the fuse 'blows', the heat of the arc that is generated melts the beads, filling the void inside the fuse and preventing a sustained arc from forming. Similarly, DC rated circuit breakers have 'arc snubbers' or magnetic 'arc blow out' devices internally that protect the breaker from sustained arcs. Generally, automotive-type fuses and circuit breakers are inadequate to the task of protecting even a moderately sized renewable energy power system.

While automotive-type fuses can and do protect low current circuits from short circuit overloads, they are only effective up to a point. Usually, the smaller gauge wiring in low current circuits works to limit the maximum amount of fault current available from the battery. Where heavy gauge wiring is used to carry large amounts of current, the fault current available from the battery during a short circuit event can easily exceed the safe limits of automotive-type protection devices, turning them into incendiary fire bombs.

Even something as simple as a switch used to disconnect a device from a DC circuit can be damaged by the arc caused by normal operating currents. Any switches that you install should be rated to well over the maximum amount of DC current that you expect the device they control to draw from the battery. Disconnect switches meant to interrupt high currents in the battery system should be specifically designed and rated for the duty of the service expected.

Every battery-powered system should have a master fuse or circuit breaker, one that is adequately sized to protect in case of a total short circuit of the main battery cables. One very popular type of fuse for this purpose is the 'Class-T' fuse, which will safely interrupt fault currents in excess of 100,000 amps. Even a small engine starting battery can produce currents in the 10,000 amperes range for short periods when short circuited.

The higher the total battery voltage, the more the risk of short circuit fault current problems. System voltages in excess of 50 Volts DC carry additional requirements, as above this voltage, the possibility of a sustained arc is greatly increased, as is the difficulty of extinguishing it once it has started.

Fortunately, Direct Current has been around for a long time, and it's properties are well understood. As battery powered renewable energy systems become increasingly popular, the availability of hardware for controlling and protecting DC circuits is getting better and the prices continue to drop.

Considering the consequences of improper battery and circuit protection, doing the job right the first time means installing equipment designed specifically for Direct Current applications. Anything less may mean that your first short circuit may be your last!

Chapter Ten - Wiring Made ¿Easy?

The subject of this month's installment was brought to the fore by an experience two nights ago while overnighting in a friend's commercially manufactured motor home. A slight burning odor was detected, but the source was not discovered until morning, an extension cord left on the ground under the coach had developed a short circuit and slowly burned the ends of the cord and the appliance plugged into it to vapor over the course of the night. The only thing that saved me was the fact that the cord had been lying on a graveled drive. If this fault had occurred inside the RV, or on any combustible material, I would not be writing this to you now.

Like the rest of your mobile electrical installation, there is nothing magic about doing wiring, and in most cases, simply following applicable codes and applying good engineering practice will result in a quite satisfactory installation. There are, however, a few caveats to installing wiring in a moving vehicle, as well as precautions to observe when working with low voltage, high current circuits. These mostly have to do with wire types and sizes, and termination connectors.

For nearly all of the wiring in your coach, you will want to use multi-stranded, flexible wiring whenever possible. Solid conductor wire, which is suitable for stationary usage in buildings, is susceptible to fatigue and failure when subjected to the flexing and vibration encountered in house truck or bus systems. Additionally, connections to the ends of this wiring will remain tighter and be more secure when stranded wire is used.

Non-metallic flexible cable is commonly used as supply wiring for AC circuits inside buildings, and is the most obvious choice for wiring the high voltage appliances in your bus. This cable is comprised of several solid conductor wires inside a single plastic sheath. This is probably the most likely wire to use in your AC wiring system, and although it is solid conductor, it is the only choice that will meet electrical codes. Unless you plan on installing your wiring inside conduit, there is no officially accepted way to use stranded wiring for AC circuits. When NM cable is installed using code-approved enclosures which have proper strain-relief clamps, you will probably experience no problems with your AC installation.

A few weeks ago, someone mentioned to me that they were considering using heavy-duty extension cord wire as AC wiring inside their bus. Although this wire is not code-approved for this application, I can see no reason why it wouldn't result in an acceptable installation. Of course, all other aspects of a code installation should be observed, and the cable should be rated for the full current of the installed circuit. This may be a way for you to install flexible stranded cables in your AC supply circuits without using NM type cable

Low voltage DC circuits are another matter. Using type NM cable is not preferred, and the solid conductors are more difficult to make a proper connection at the ends, where smaller-gauge wiring will be more common at appliances, etc. Low voltage wiring will need to be protected from abrasion and damage, but otherwise it is usually acceptable to run wiring inside of walls and other spaces without the use of conduits. In many cases, you may choose to not install an enclosure behind the device (light fixture, switch, etc.). This means that you also will not have the benefit of proper strain relief on the wiring. The possible outcome of this is that movement of the wire while you are on the road will cause flexing of the cable, which results in fatigue of the wiring and eventual breakage and failure of the wire. Stranded wiring is better able to cope with this flexing, and is easier to work with. Solid conductor wire is notoriously difficult to stuff into confined spaces and to run around obstructions.

All wiring should be of the proper gauge to carry the full-rated current of the circuit which it supplies. Low voltage wiring actually should be oversized to minimise voltage drop in the circuit. This is particularly true in high current circuits such as inverter supply, battery, and starter motor cables. In low voltage circuits where the current exceeds 20 or 30 amps, special fine-strand wire is best used, such as electric welding cable. These cables are fairly expensive, but are better able to carry high currents with less loss. They are super flexible and have a very tough rubberized insulation which will stand up well to abrasion, punctures, and acid from the batteries.

Next time we will investigate the various methods of installing terminating connectors to our wiring.

Chapter Eleven -

Connectors and Terminals

Because all of the wiring in a house truck or bus is subjected to vibration and extremes in temperature and humidity, installing your wiring using the proper connectors is of the highest importance. Many of the circuits in use will be low voltage battery power, some with significantly high current flowing through the wiring. Keeping voltage drop to a minimum is essential, as is insuring that connections stay tight throughout the life of the installation. Use of connectors designed specifically for the job will make these goals easily attainable.

As we discussed last issue, the majority of wiring in your vehicle should be stranded-type wiring, which is very difficult to properly 'wrap around' screw terminals. For this reason, you will want to install 'ring' or 'spade' crimp-on terminals to make connection to screw-type fixtures. These terminals come in a variety of wire and stud sizes, and you should try to select the size that best fits both the wire and the screw/stud that you will be connecting it to. Specialised pliers are used to provide the 'crimp' that retains the wire and makes the connection. The successful installation of these terminals depends on use of the proper tool. Larger wire sizes may use 'crimp'-type connectors, or alternately, a pressure-type connector, with the pressure provided by some means of a screw device. Selection if the proper connector for the wire size is even more important with these type of connectors. Nearly all types of crimp connectors will benefit from the correct application of solder after crimping. This will lessen the resistance of the connection, minimising associated voltage drop.

Insulated crimp connectors, aren't very convenient to solder, so if you know you will be applying solder to your connections, use uninsulated terminals, and apply heat shrink tubing after soldering. This inexpensive tubing comes in a variety of sizes and colours, and can be written on with an indelible pen to identify wires. Installing crimp terminals on solid-type wire is always a loosing proposition. You will find that the connection will nearly never remain tight. Soldering these terminal in place is the only way to insure a tight connection. NOTE: Wires that are to be inserted in a pressure-type connector (or placed directly under a screw terminal) should NEVER be coated with solder before installation!!! Solder is a semi-solid liquid, and will 'relax' over time, leaving your connections loose and unreliable.

In general, you should avoid using twist-on wire connectors whenever possible, except, perhaps, in line-voltage AC wiring, and then only inside approved enclosures. While these 'wire nuts' are capable of making a secure connection, they do nothing to prevent intrusion by water, bugs and stray conductive objects, and they do not stand up well to stretching or abuse from flexing.

Connections made directly to battery terminals require special consideration. If your batteries have automotive-type round posts, use standard cables or cable ends to make your connection. Lead battery cable ends are pretty well acid proof, and are easiest to install and maintain. Screw post-type battery terminals are a bit trickier, as regular brass or tin-plated copper connectors are susceptible to corrosion and don't hold up well. Aluminum pressure-type connectors are also risky business here. The best bet is to use commercially available anti-corrosion terminal pads, and liberally coat any terminals on the batteries with an anti-corrosion coating. Crossing your fingers and cleaning the battery tops often won't hurt either! Any hardware you use here, such as washers, nuts, etc., should be made of stainless steel for best durability. Resist the temptation to place more than one wire in a connection before crimping or soldering it. Most likely, you will regret it later when the wires need to separated due to a wiring change. Crimp terminals are also difficult enough to align and neatly dress in a wiring loom, the more wire contained in a single connector, the harder it is to do an orderly job of it (and neatness counts!).

Chapter Twelve -

Wire and Cable Management

Avid readers of this column will, by now, have quite a collection of wiring in their mobile house, what with battery cables, inverter wiring, lighting circuits, AC supply, DC branch cables, and all of this interconnecting spaghetti that makes the various pieces of the puzzle work together.

What is needed now (or perhaps much earlier) is a way to keep all of this wiring neat and orderly. Using the old trick of wrapping the cables in black electrician's tape is barely adequate, as the tape tends to get gummy after a time, and while the wires are protected in the tape, they are also impossible to follow, repair or replace without removing much or all of the black plastic covering.

The goal of bundling and routing wiring is made much easier by the use of several inexpensive and easily available commercial products. The first, and most useful is the common nylon wire tie. These self-cinching plastic straps come in a variety of widths and lengths, and can also be procured in various colors as well. Some wire ties have an eyelet in the end, which makes them perfect for creating wiring looms attached to wood or metal surfaces with screws. Placing a wire tie around bundled wiring every few inches can be a very effective way of preventing damage and keeping wiring neat and out of the way.

In places where screws can not be used to secure the ties, self-adhesive mounting blocks which have a slot for the wire tie to pass through are available. The double-sticky foam tape holds fast to nearly any clean surface. In many cases where wiring is routed across wood surfaces, the ties can be passed through the loop formed by common round-headed staples.

While installing cabling in radio stations, I sometimes go through a thousand or more cable ties, cutting apart bundled wiring under counters and inside racks to add additional wiring as the project progresses. They are a very effective way of creating custom wiring harnesses when a line of ties are installed and then used to route wires between locations.

In places where wiring will be subject to physical damage, or where wires pass through normally inaccessible areas, place your wiring inside flexible non-metallic conduits. Even suitably sized rubber or plastic garden hose will make the job of adding or replacing wiring running through a closed or inaccessible area much easier. If you plan on running wires through your floor, walls or ceiling, and you ever think you may need to access it for changes in the future, you'll be very glad to be able to 'fish' your wiring through a conduit, instead of tearing out the woodwork to get at the wiring inside.

Labeling wiring and cables is an extra-credit exercise, but a well thought out numbering system and indicating charts will save untold time when changes or repairs are attempted years in the future. All manner of labeling products exist, from numbered self-adhesive tape, to peel-off legends, all the way up to complete labeling systems which allow you to enter text on a keyboard and then print on an adhesive wire marker. Personally, I prefer writing a short description of the wire's purpose using a sharp-point permanent marker on a piece of white heat-shrink tubing, which is attached to each end of the wire.

Now I am going to give you a tip that is worth it's weight is gold (how much does a 'tip' weigh, anyhow?), and that is to always leave a little extra wire at each end of the wire's run. This is called 'service loop', and you will be pleased that you provided yourself an extra inch or two of wire when you need to move a terminal to a different connection, repair a damaged or corroded end, or move a piece of equipment a few inches in one direction or another to make room for something else. Basically, a service loop is when you by-pass the device you are connecting the wire to and then loop back to make the connection, leaving extra wire. For devices which are not accessible from the rear, leaving an extra half-foot of wire or more wouldn't be extreme. Imagine trying to connect or disconnect a lamp or switch which won't pull far enough from the wall to let you get your fingers behind it! Aaaarrgghhh! Wire is cheap, use enough of it to make working with it easy. You'll end up with a more reliable system, as the connections won't be strained, and you'll be able to make sure each connection is secure and solid.

Chapter Thirteen - Wind Power

This issue, we are taking a side trip in the renewable energy realm to explore the production of electricity from wind sources.

Wind power has been around for centuries, what's more picturesque than a Dutch windmill? Using wind to produce electricity began in earnest in the US in the early 1930's, when many small stand-alone wind systems were installed in rural farms and residences to charge the batteries necessary to run the instruments of the latest electronic craze, radio. Wind generators ranging in size from 100 watts up to several thousand watts were marketed and installed, bringing new power and conveniences to remote homesteads across the country.

The push for rural electrification in the late 1940's and 50's put a quick end to the growing industry of wind generator manufacture, as most grid power companies required the removal of existing wind generators as a condition to connection of service. Many perfectly functional wind plants were decommissioned, often times by toppling the towers they were mounted on with the generators still in place.

A revival of interest in wind energy in the 1970's and early 80's brought many of the more carefully removed machines back into service, as wind power hobbyists and aficionados scoured the barns and garages of the country looking for retired generators. The Jacobs 32 volt, 1,500 watt wind plants are still in great demand, and one can also find old Winco Winchargers in service all over the country.

Today, wind generators are manufactured using modern materials and computer designed airfoils and electronics. Interest in utility-scale wind power is on the rise, and rows of huge machines are frequently installed on ridge tops, where a significant quantity of power can be harvested and fed into the utility grid.

Traditionally, mobile installations of wind generators have been mostly limited to sailboats, but there is no reason that you couldn't install a small system on your house truck or bus. Wind power is the lowest cost per-installed-watt of any renewable energy source, only about 20% of the cost of photovoltaic modules. Of course, you do need a good source of wind, otherwise the investment may not be worth exploring.

Generally, a wind generator is installed on top of a tall tower, which places it in the greatest supply of 'clean' wind, that is, wind that has no turbulence produced by obstructions such as trees, buildings, etc. Of course, a 60-90 foot tall tower would be rather inconvenient to carry around and erect when you are traveling in a vehicle, so you will need to compromise and construct a mount that is as tall as can be made, but still collapsed enough to store away for the road. Here's where things get really tricky...

By nature, wind electric machines produce vibration. Even a very well-balanced machine will experience vibration caused by wind turbulence, bearing noise, pitch and yaw, and dynamic imbalances caused by the rotating blades shifting position to track changing wind directions. For this reason, it is usually a very bad idea to mount the generator on your roof, or have it connected in any way to the structure of your living space. Any vibration will make itself known immediately, as your bus will shake, rattle and roll with each changing of the breeze.

What to do? Well, for a temporary installation, I favor a steel plate that can be driven over by a tire, allowing the vehicle's weight to act as ballast to keep the tower upright. A socket on the plate mates with the base of the steel pipe that forms the tower. Any vibration will be dampened by the tire and contact with the ground or pavement. Obviously, the tower may only be 15 feet or so in height, but when parked at an exposed windy location such as the ocean shore or a bare mountain top, you should be able to harvest a wealth of free energy. Unlike solar electric sources, wind energy can be available 24 hours a day. And before you ask....NO, it is NOT possible to use the wind generator to recharge your batteries while you drive down the road!

Should you consider constructing your own wind electric generator, be advised that it is not as easy as might be expected to construct a high-efficiency, well-balanced and reasonably functional wind plant. Considering the prices of smaller wind machines these days, your efforts might be better put to use earning the purchase price of a new or used commercially-made machine.

In any event, the sight of a spinning propeller atop your rolling home is sure to make you the star attraction wherever you roam. Nothing brings attention faster than kinetic sculpture.

Chapter Fifteen - Refrigeration Basics

Readers my be wondering if ol' Sharkey has developed a case of brain barnacles. Refrigeration? I thought these articles were about renewable energy. Providing power to preserve perishable provisions can be the biggest consumer of energy in a home or bus based electrical system. Even if you are using an icebox to keep food cold, you are still consuming energy, and paying for the privilege. This series of articles will help you get the most from your refrigeration system, whatever it's type.

To begin, let's consider the common icebox or insulated cooler, supplied with a block of ice to keep the food cold. The process of refrigerating with ice is a lot more complex than you probably thought. The ice doesn't keep the food cold simply because it is cold itself, but because the ice melts.

To understand why, it is necessary to know a bit about thermodynamics (just a little bit, OK?). Consider a pound (.45Kg) of ice, with a temperature of, say, zero degrees Fahrenheit (-18°C). This ice will absorb one BTU (British Thermal Unit) of energy for every one degree it's temperature rises, up to the melting point of 32° (0°C). So, as this ice warms up by absorbing heat from your food, it will gain 32 BTU's. So far so good, but an astounding thing happens when the ice changes states, from solid to liquid, it absorbs 144 BTU while rising only one degree F! Once all the ice is melted, the melt water reverts to again absorbing one BTU per degree F of temperature rise.

From this we can see that the melting of ice is 144 times more efficient at cooling food than either solid ice or the cold water left after the ice is gone. In fact, if the ice didn't melt, it wouldn't do a very good job of cooling your grub. A 25 pound (11.34Kg) solid block of ice would absorb 3,600 BTU's of heat while melting, or the equivalent of more than one kilowatt hour of electrical power.

In this example, we considered ice to be frozen water, but in reality, it could have been any one of many substances. The laws of thermodynamics apply to the changing of states of all matter, solid to liquid, liquid to vapor. Obviously, we need to choose materials that have a melting point close to the temperature that we wish to cool to. Attempting to refrigerate food by melting candle wax, or lead would be an exercise in futility. Water very conveniently changes states very near the optimum temperature for retarding spoilage in food.

One of the more efficient ways of keeping things very cold is 'dry ice', which is frozen carbon dioxide, with a melting point of approximately -100°F (-78.5°C). Because it has such a low melting temperature, dry ice can keep foods like ice cream quite solidly frozen. It is also a bit dicey to work with, as it can quickly freeze the tissues of your skin while being handled.

Where better thermal efficiency is desired, compounds called eutectic solutions are used in place of water ice. Basically, these are anti-freeze solutions of brine or glycol that have a melting point in the range of -60 to 32°F (-50 to 0°C). In the States, one commercial product known as 'Blue Ice' is very popular as a substitute in ice chests and picnic coolers. The sealed packages are refrozen and reused repeatedly. Eutectic solutions have the advantage of being able to absorb more BTU's per volume than plain water, and will last longer while giving lower cooling temperatures.

In the next article, we'll investigate basic mechanical refrigeration in several forms.

Chapter Fifteen - Mechanical Refrigeration

Keeping Your Cool, Part 2

Last issue, we learned the basics of refrigeration. To recap, when a substance changes states (solid to liquid or liquid to gas) a heckuvalotta heat gets absorbed. For most of the 'civilized' world, this cycle is sustained by mechanical refrigeration.

Most household refrigerators use a standard configuration which relies on an electric compressor to pressurize and circulate a refrigerant gas, which is then evaporated inside the food compartment, absorbing the heat from the contents. The gas is then caused to condense outside the refrigerator, whereupon it dumps its heat which is radiated to the surrounding air, and the cycle repeats, reusing the same refrigerant gas over and over.

Very early, ammonia was found to be an effective refrigerant gas, although it is extremely toxic. Most modern consumer-style refrigerators use Freon® gas, which, while being less toxic, has a now well-known effect on the Earth's ozone layer. Ammonia is still in use in large industrial refrigeration units.

While compressor refrigeration is a fairly efficient process, with about three time as much energy transferred as consumed, the quantity of energy required on a daily basis is comparatively large when considered in terms of being supplied from storage batteries. Even ultra-efficient refrigerators which are purpose-built to be run from renewable energy power systems use a substantial amount of power, and require a reliable supply of charging current to be available regularly.

In most situations where grid power is not readily available, absorption refrigeration is commonly used, mainly in the form of the gas powered RV refrigerator. These refrigerators use the same basic principles to keep food cold (evaporation/condensation), but are able to do it without the need for a compressor. Instead, these units rely on the properties of thermal motion (heat rises) to move the refrigerant through the closed loop of the system. The heat that drives the refrigerant can come from a variety of sources such as LP gas, electricity, paraffin, diesel, etc.

Because these refrigerators do not have a compressor, they are more sensitive to outside influences such as being out-of-level, and if caused to run too hot can develop 'vapor lock', which prevents them from circulating the refrigerant. You may have heard of the common repair for this vapor lock, which is standing the icebox on it's top for a day or two. It sounds kooky, but it works!

When operating properly, an absorption refrigerator can be used to cool and freeze foods, and will run absolutely silently for many years, as there are no moving parts to wear out (except maybe the door!). My personal experience is that my medium-sized RV refrigerator consumes about ten gallons (38 liters) of LP gas per month. Of course, when grid power is available, this is used instead of the gas to fuel the refrigerator.

Another form of non-compression refrigeration is based on thermoelectric principles. Without going into excruciating details, a device known as a Peltier Junction Semiconductor (kind of like a big transistor) is fed electricity. The effect is that heat is transferred from one side of the junction to the other. Unfortunately, the efficiency of these devices is very poor, with nearly twice as much energy being consumed as is transferred. Small electric picnic coolers are manufactured using these devices, but unless you have quite a supply of inexpensive electricity available, they are nothing more than curiosities.

Recently, some intrepid experimenters have devised a simple machine that uses ammonia gas to produce a goodly quantity of ice using nothing more complicated for power than pure sunlight. Simply described, it uses concentrated solar radiation to pressurize and condense ammonia, which is then stored in a pressure vessel. After the sun sets, the ammonia is then allowed to expand and evaporate in tubing inside an insulated box, where it absorbs the heat from containers of water. This device has been shown to bring a higher standard of living to less developed populations without introducing new and consumptive habits requiring the purchase of fuels and machinery.

Perhaps there is also hope for the rest of the planet...

Chapter 16 - Engine Charging

Some dozen or so articles back, I mentioned that charging your house batteries from the vehicle's engine is the most difficult of all methods of replacing your household consumption. This issue, we'll examine some of the methods available and suggest some alternatives

By far, the most popular methods of recharging house batteries in a vehicle are solenoids and isolators. We will examine these systems individually, after noting that each has the same effect, that is to connect the house batteries to the engine starting battery charging system. Each has disadvantages, which, for your purposes, may or may not be offset by their individual advantages.

First, solenoids. A solenoid is an electrical device that can connect the house and engine batteries directly together, effectively making them one battery bank. The solenoid is usually controlled by either the vehicle's ignition switch, or by a switch that is operated by the driver. Sometimes, both controls are used, that is the solenoid will only connect the batteries together when the ignition switch is on and the driver manually calls for the batteries to connect by operating the switch, pulling in the solenoid.

What is supposed to happen then is that the alternator (or generator on older vehicles) charges both batteries until full. What actually happens most often is that the engine battery drains into the discharged house battery and the alternator has to recharge two half-dead batteries. On a long trip, this probably will happen eventually, but at a cost, which we will observe later.

Advantages of this type of system are that it is quite inexpensive to install, may be completely operator transparent (ignition switch operation only), and in a pinch, the house batteries can act as a jump start for a dead engine battery, getting your rig back on the road in an emergency.

Disadvantages include the possibility that a very dead house battery will drag the engine battery system down enough to cause electrical and starting problems. Leaving a manually operated switch in the wrong position can result in both dead house and engine batteries, so care is suggested in this system.

Isolator-based systems overcome some of the shortcomings of solenoid charging systems. Basically a battery isolator is a dual high-current diode bridge that completely hides one battery from another as far as loads are concerned. Think of it as a couple of one-way valves that only allow the flow of current to go one way, into the batteries. In this manner, draining either battery completely dead will not affect the other battery's state of charge. When the engine of the vehicle is started, the current from the alternator can flow into both batteries, replacing any charge that was used in house lighting or engine starting.

Advantages of the isolator are that operation is completely transparent, the driver has no switches or other controls to remember to operate. Engine starting and running should be unaffected by the state of charge of the house battery.

Disadvantages include a higher initial cost and installation into the vehicle's charging system requires that modifications be made to the factory wiring.

While literally thousands upon thousands of recreational vehicles use one of the two systems described above, the both have one very serious disadvantage that cannot be overlooked by anyone who is serious about installing an electrical system in their house truck or bus that is as efficient as possible, and provides that best possible charge for longest battery life. The fact is that engine charging systems are optimised for charging the engine starting battery and running the vehicle's electrical accessories, NOT recharging deep-discharge storage batteries that are the proper type for a renewable energy system. Neither the charge rate (amount of available charging current) nor terminal voltage are correct for deep-discharge battery health.

Engine battery charging systems are optimized to replace a very small amount of discharge very quickly. Starting your vehicle's engine takes only a small portion of a battery's capacity, so in an isolator-based system, once the engine battery is full, the alternator stops putting out much current, and the house batteries don't recharge fully. In a solenoid-based system, the alternator sees two badly discharged batteries, and tries to really cram a lot of current into them all at once, possibly damaging the house batteries, and likely doing the engine battery some damage as well.

Properly, what is needed is a separate charging system for each battery system, which is exactly what we will take up as a subject next issue!

Chapter 17 - Engine Charging -

The Right Way

Our previous month's installment gave us an overview of some of the more common methods of charging house batteries from a vehicle's generating system, and touched upon the advantages and disadvantages of each system. This issue, I'll expound on my opinion about the only correct method of using an internal combustion engine to replenish energy removed from batteries, using a separate alternator/generator which is dedicated only to the house batteries.

Installing a second alternator in your house truck or bus for the purpose of keeping your house batteries charged might seem like a lot of extra expense and work, but the results will be more than worth the effort. As we have learned, deep-discharge batteries should be charged at very specific currents, and the terminal voltage should be regulated carefully at each stage of the charging cycle. Attempting to control the current and voltage from an alternator that is also trying to charge your engine starting battery and run the loads and accessories in your vehicle is asking too much of a system that was designed by the manufacturer for a single purpose.

The nuts-and-bolts of such a modification to your engine is beyond the scope of this series of articles. In some vehicles, extra pulleys are available to run the second alternator, and convenient tapped bolt holes will allow the physical mounting to be accomplished. In other cases, there may not be enough room under the bonnet for the added equipment, or specialized brackets and mountings may need to be constructed to securely mount the new alternator. Each installation will present its own features and problems.

In any event, if a second alternator is installed, a purpose-built regulator must be installed to take advantage of the separate circuit to charge the house batteries. The stock factory regulator will not be sufficient to do the job, as it is engineered (again) to charge engine batteries and run vehicular accessories such as lights, heater, wipers, etc. Crafty truckers with electronic assembly skills will be able to construct their own regulators. Those who cannot cobble components will need to purchase ready made regulators, built for the task

An interesting aside is that if you aren't finding yourself moving your house truck or bus very often, and need to charge your batteries from an engine, a 5 - 8 horsepower horizontal-shaft, one-cylinder engine can be rigged to an alternator of this type to provide the needed charge without the necessity of running your vehicle engine for hours on end.

Not to leave you hanging without providing some support documentation, the following few paragraphs will allow the reader to access more information on proper alternator regulators, and provides some fairly descriptive instructions for building your own engine-generator:

Home Power Magazine is by far the most prolific source for information about charging deep-cycle batteries, and Renewable Energy in all forms:
     Home Power Magazine
     P.O. Box 520
     Ashland, Oregon, 97520, USA
     On the Internet: www.homepower.com
An article written by Richard Perez, editor and publisher of Home Power Magazine, describes an engine-generator construction project, and includes schematic diagrams and parts lists for the "Mark 8" regulator. Contact Home Power by mail and request a copy of back issue #42, which contains the article.

Another interesting and information-filled article is available on the Internet at: www.theepicenter.com/tow02077.html This is a very detailed description of constructing an engine-generator system, with several possibilities of engine types and alternator configurations, and gives important details on choosing pulley sizes, belt types, etc. I would caution the reader to ignore this sites' repeated insistence that only a self-regulated alternator be used, as this is exactly the wrong type of power plant for our purposes.
Readers may also be able to procure copies of this article by contacting:
     Epicenter Supplies, LLC
     384 Wallis St. #2
     Eugene, OR 97402, USA
     (541) 684-0717

Hopefully, I haven't given away too many of my carefully-guarded information resources in this episode.

Chapter 18 - Biodiesel Fuel

Up until now, all of our explorations into Renewable Energy have been associated with the production, storage, distribution and consumption of electricity. Over the course of the last month, I have been researching avenues of home production of diesel motor fuel from vegetable oil. This fuel, which is fairly easy to make using some commonly available chemicals using a variety of common utensils, is known as Biodiesel.

Biodiesel fuel has the potential to revolutionize the motor fuel industry. For the first time, motor fuel can be manufactured from domestically produced materials, freeing dependence from foreign oil producers, and eliminating environmentally destructive drilling, super tanker transport ships, and other expensive and unsustainable practices. In addition, Biodiesel reduces pollution emissions from diesel engines up to 90%, is cleaner burning, reduces required engine maintenance, has better lubricative properties, and best of all, the exhaust smells like french-fried potatoes. Biodiesel is easily made from waste vegetable oil, a product of fast-food and restaurant fryers which is frequently considered a disposal problem. Many individuals are able to obtain the used oil free of charge from these establishments. Imagine being able to get free motor fuel from old chip pan oil!

Properly made Biodiesel can be used for fuel in any diesel engine without modifications of any kind. It can also be used to fuel domestic space heaters and furnaces at a substantial savings in expense. Blends of Biodiesel and regular petroleum diesel fuels are also possible. Blends of as little as 1-2% Biodiesel are shown to improve engine life and cleanliness, and concentrations of 20% Biodiesel have demonstrated the ability to reduce tailpipe emissions and smoke as much as 60%.

A significant reduction in the production of global carbon dioxide is possible if petroleum diesel fuel was largely replaced by the use of Biodiesel, which produces no net gain in CO². The carbon molecules present in Biodiesel once existed as free CO² in the atmosphere before being locked up in the growing plant's cells. Burning the esters contained in Biodiesel releases these carbon molecules back to the atmosphere where they originated. Petroleum based fuels, on the other hand, release carbon that has been trapped out of circulation for millions of years. Such additional carbon dioxide in the earth's atmosphere is generally recognized to be the cause of global warming.

Any form of fatty oils from vegetable or animal sources can be converted into useable fuel. These oils contain esters, which are the part that is valuable as fuel, and glycerin, which is a waste product in the fuel production, but a potentially valuable substance when used in the production of soaps, lotions, skin oils, and more. The process of separating these elements from the oil is called a reaction, and afterwards, the esters (fuel) and glycerin form stratified layers in the reaction vessel, and are simply drained off to their respective storage containers. If not utilized as a product in it's own right, the glycerin can simply be composted. Production of Biodiesel produces no pollutants. In fact Biodiesel itself is non-toxic and biodegradable. It can be handled and stored exactly like petroleum fuels.

Although the process of converting vegetable oil to fuel is not difficult, I would encourage anyone who is interested to study the process thoroughly, and understand what safety precautions are necessary before attempting to use the chemicals involved.

Simply described, a measured volume of vegetable oil is mixed with a solution of methanol and household lye (sodium hydroxide). This mixture is then heated, stirred for an interval, and then allowed to settle. Further adjustments to the pH of the fuel product, and "washing" to remove free fatty acids and excess methanol are usually required, and are also not difficult to accomplish. The product of this process usually requires no further finishing and is useable as fuel immediately.

Many individuals world-wide are producing all of their motor fuel by this process, and there is a fledgling industry of organized Biodiesel producers who see this fuel as a valuable income producing venture for the future.

While mucking about with vats of hot oil while traveling may not seem to be the best form of recreation, consider the savings in fuel expenses, as well as the possibility of becoming a traveling educational institution. This may be a worthwhile craft to hone for traveling road shows as well! Make enough fuel for yourself, then sell some for spending cash!!! (Be sure to watch out for the Taxman, remember that road fuels are usually heavily taxed).

Chapter 19 - Water Purification

Recently, while responding to an inquiry about collecting drinking water from the roof of a house bus, I had the opportunity to launch into a fairly detailed sermon about water quality. Here, for your pleasure and education is the body of my knowledge on the subject:

While it's unlikely that water from a reasonably clean roof would be any nastier than what comes out of city water pipes, those of us who live in portable dwellings are likely to meet up with a variety of unknown water conditions, from contaminated well water, water drawn from pipes or tanks which may contain impurities, hose bib connections which might have been used for chemical or sewage system cleaning, or even ground water in the back country which looks clean enough for domestic use. Sometimes it's necessary to use water wherever you can find it, but if you want to be certain of it's purity, run it through a proper filter first.

By proper filter, I mean a water purifier, such as a ceramic-coated carbon block filter. The hardware store pleated or spun fiber filters will only remove particles. The carbon granule filters they sell for taste/odor removal are next to useless as well. A true water purifier will remove chemicals, heavy metals, pathogens, pesticides, bacteria, both dead and alive, and any other stuff that you shouldn't put in your body. Most carbon block filters are tested to remove 99.9% of unwanted impurities.

There are several good filters out there, some are quite expensive, such as the Multi-pure, which is often sold through multilevel marketing schemes, and the markup is outrageous. I bought mine from a distributor, and it was still $325.00 (USD) Although the filter cartridges themselves are not overly expensive, the canisters which hold them are specialised, and must be used in order to utilise this brand of filter.

My all-time favorite system is comprised of a standard hardware store cartridge-type filter housing with a Doulton ceramic carbon block filter inserted instead of the pleated or carbon granule filter cartridges that the filter is usually fitted with. The filter housing shouldn't set you back more than $25, and the Doulton filter is about $40 (all USD). If you buy online or mail order, be sure to specify the proper 'candle' (that's what the manufacturer calls them) for a standard filter housing. A few bits of polyethylene tubing, and a dedicated spigot and you're in business! You can pay for the fancy filter-type spigot, but I just went down to the salvage parts store and bought a nice old single unit off of an antique lavatory, the kind with separate hot and cold taps, works just fine and has the proper look for my Housetruck's interior.

Although you could probably scoop water out of mud puddles and get crystal-clear water out of this filter, I recommend putting the standard pleated or spun-fiber filter ahead of the ceramic filter, it catches the large pieces of rust, scale, etc. This requires a second filter housing, but keeping the crud out of your water heater alone is worth the cost. Remember that the ceramic filter will have a definite life span, so you will want to use it only for drinking water, and use the water that comes out of the pleated filter assembly for washing purposes, reserving the purified water for your own consumption.

Water can also be purified by reverse osmosis (RO) process, but this removes much of the minerals that are beneficial to good health, and RO filters waste two gallons of water for every one gallon they make. A pressurized water system is also required. In the case of very polluted water, a RO filter followed by a carbon block filter has proven to be very effective.

For readers without pressurised water systems, some very good gravity-operated filters are available, some which resemble a water pitcher with a carbon filter fitted into the lid. Outdoor equipment stores sell small hand operated pump filters that can be trucked into a back pack.

Note that if your water system uses a "water softener", you should install any water purification devices before the softener, or they will be rendered inoperative almost immediately.

As for using water purification tablets, I'd pass unless it was some kind of emergency. These are usually concentrated chlorine, and perhaps other chemicals, intended to kill bacteria in the water. Personally, I'm trying to consume fewer poisonous chemicals, not more, and dead bacteria are as unpalatable to me as live.

I've been drinking purified water for over 20 years, and enjoy splendid health. I won't even touch the stuff that comes out of city pipes, one taste of the chlorine and I spit it right out (well, sometimes I'm a bit more polite, especially if I'm in a restaurant).

Gotta go, I'm getting thirsty just thinking about it...

Chapter 20 - Communications on the Road

Although it might be easy to take it for granted in these days of pervasive cellular telephone service, a variety of other communications services are available to the intrepid traveler for use in both local and long-distance needs.

The need to contact another person may range from being able to call the kids in from the playground, assisting the driver of your truck or bus while negotiating a tight parking spot while standing outside for a clearer view, or being able to call for roadside assistance or to locate the best and nearest pub in unfamiliar territory. While no single radio service will satisfy all of these needs with one instrument, being aware of the choices will help identify the proper service and equipment to do the job properly.

Most familiar, and probably least expensive is what we in the States call "Citizens Band" radio. The 40 channel transceivers are ubiquitous, which makes this type of radio a good choice for being able to contact other operators. While it is possible to get everything from a time check to a tow vehicle by calling out on these radios, the frequency is very crowded, prone to severe interference, and not very private. Short range communication, such as between two vehicles traveling together, or between several radios in close proximity is very good. The operating frequency of 27MHz allows the signal to travel quite a distance, which can be both a blessing and a curse. A blessing if you are trying to contact someone who is over the horizon, and a curse because you will also be talking with 200 million other CB radios worldwide. The general demeanor of the CB radio band is loose and usually friendly, like the internet, anything goes and usually does. No license is required to own or operate these radios

For more reliable radio service, consider amateur (Ham) radio service. Available on a variety of frequencies, this service is held to a high standard of performance. Licenses are required, and amateur radio operators tend to police their own behavior. While idle chit-chat is tolerated, it is expected that you surrender the frequency, or at least yield use of it, when other operators request access. Equipment for this service is usually of high quality, and many amateur radio operators build their own. Ham radio offers the distinction of being able to allow communications which are virtually world-wide, due the operating frequencies involved and helpful nature of the majority of operators.

Recently, Personal Radio Service (FRS) has become popular. These medium-cost units deliver clear communications over limited range. Privacy is usually fairly good, but as there are a limited number of frequencies available, you may find that you are sharing a channel with others, particularly in urban areas and at special events which have many attendees.

Most reliable and private over short distances would be licensed business-band radio transceivers. These VHF or UHF radios usually are licensed to only one user per locality, and although it is possible to eavesdrop on conversations through use of a scanner radio, the security of conversations is better than with most other services. Traveling with these radios can be tricky, as itinerate users may have to use alternate frequencies to avoid interfering with the local radio services in the towns that they pass through. Most business-band users will not tolerate interference on "their" frequency, so coordination of channels used is most important.

Nearly all of the radios discussed are available in configurations that allow them to be powered by mains power, 12 volt vehicle batteries, or disposable/rechargeable penlight cells. Many units can enjoy enhanced performance with the use of outside antennas, and all are available as hand-held "walkie-talkie" units.

Whichever radio service you may decide to utilize, be sure to keep your concentration on the road while using them while driving. Many comfortable headset devices are available these days that allow a driver to have hands-free use of a phone or radio, so that safety isn't compromised during the conversation.

As Stephen Hawking said (on a Pink Floyd album) "All we need to do is keep talking..."