The basics of Electrical Power
If you've decided that you need to generate power, Details 8, 9, 10, 11 and 12 provide an
educated layman's introduction to the subject. It's purpose is not to give you a crash course in
electrical engineering. If you are not particularly handy with tools or experienced with
electricity, you will probably need to hire some expertise if you go much beyond plugging an
extension cord into a portable generator. If you attempt to do this based on these instructions
alone, you do so at your own risk. Warning: electricity can kill you, improper installation of
electrical components can cause fires or damage to sensitive equipment.
Investing in power generation can be a significant factor in preserving the safety and security of
your family and neighborhood in the event of a prolonged loss of power. During the 33 day
blackout that resulted from the winter ice storms of 1998 in Quebec, the single most useful piece
of equipment in the recovery of neighborhoods was the small portable generator. However, most
of these generators relied on fuel that was trucked into the area (this was organized by local
governments and emergency management officials). In the event of Y2K disruptions (or any
other wide-spread disruption), the ability to have fuel hauled in may be problematic, as well a
supply of extra generators available for deployment in affected areas..
THE VERY BASICS
Electrical Power comes in two forms: AC and DC.
AC, or Alternating Current, is the power provided by your electrical utility or your own
generator. Generators make a reasonably clean AC power source and can power just about
anything that normally runs on utility power.
DC, or Direct Current, is the type of power supplied by batteries, solar panels, and older
automobile generators. DC is not as efficient as AC for long transmission paths as it produces
more resistence than AC for the same amount of power. The voltage of DC cannot be stepped up
or down by transformers like AC can. AC is more efficient with less line losses than DC but
cannot be stored in batteries.
AC can be converted to DC and DC to AC.
The equipment that transforms DC to AC is an invertor. DC power goes in, and AC power
comes out. These invertors could be considered to be a generator that runs on DC battery
electricity instead of gasoline, propane, or diesel fuel. They receive battery type DC electricity
and covert it to AC electricity that can power household appliances. One advantage of modern
invertors is that they are totally quiet as compared to the roar of a gasoline generator. You can
use a generator several times a day to cool the refrigerator, freezer, recharge batteries, and run
other large intermittent loads. At bed time, the house electrical system can be switched from a
generator to a battery bank driven invertor. The invertor allows 110 V lights and some
appliances to operate from energy stored in batteries. Because of the enormous power needs of a
home, an invertor cannot be expected to produce as much power as a generator, and the amount it
can produce is limited by what goes in from the batteries. Even a relatively small invertor must
have a large battery bank to supply very much power.
Going the other way, AC power produced by your generator can be stored in the batteries by
using a rectifier to convert AC to DC. Battery chargers and automobile voltage regulators have
rectifiers in them for this purpose. A battery charger does just the opposite of what an invertor
does. A battery charger makes DC electricity from AC electricity and an invertor makes AC
electricity from DC electricity. It is generally easier and less expensive to convert AC to DC than
DC to AC. That is why invertors cost so much more than battery chargers. Many invertors are
both battery chargers and invertors. With AC supplied to the invertor, it charges the battery
bank. When AC power is interrupted, the invertor stops being a battery charger and becomes an
invertor supplying 120 V out to the system that had been supplying it 120 V to maintain the
The basic measurements and formulas you need for figuring power are:
Volts Volts are like the pressure of water in a garden hose
Watts divided by amps equals volts
Watts The amount of work done (like horsepower)
Volts times amps equals watts
Amps Amps are like the volume of water in a garden hose.
Watts divided by volts equals amps
An incandescent 12 volt light bulb at 10 amps will produce the same light as a 120 volt light at
one amp. Both will produce 120 watts. This is basically true whether we are using DC or AC
electricity. Purely resistive loads like an incandescent light bulb work essentially the same on
AC or DC. Motors and electronic devices are another subject. Never use AC on a DC device or
visa-versa or damage will probably result, even if the voltages are correct. Unless the device
specifically states the required voltage can be AC or DC, you must use the type of electricity
OK, so now you know you need amps and volts to produce watts. The question is: where do you
get the amps and volts?
SOURCES OF AMPS AND VOLTS
1. Fossil fuel (gasoline, propane, diesel)
2. Alternative fuel (alcohol or vegetable oil, corresponding roughly to gasoline and diesel, see also methane gas and producer gas))
3. Wind, Water, and Solar.
The actual generating of power is discussed in the section GENERATOR DETAILS.
Volts and amps (power) generated by these sources can be used:
1. To charge batteries;
Batteries can be used to power DC devices such as radios, CD players, televisions, food
processing equipment, vacuum cleaners, lights, etc. With an invertor, batteries can be used to
power AC equipment.
A step-down voltage regulator may be necessary to convert the 12 volt DC battery voltage to
whatever lesser voltage is required for some lower volate DC appliances like radios. Step-down
voltage regulators can be electronic devices which are very efficient or they can be just resistors
which waste much of the input power to reduce the output to a specified lower voltage. These, as
you can imagine, are not as good for prolonged use on battery as they waste so much power. The
electronic type voltage reducers are more efficient but cost more and are harder to find. They
are, however, not hard to assemble if you have the talent and inclination to pick up a soldering
iron to make your own. The key is using ready-made voltage regulator chips that eliminate much
of the construction of earlier designs. Schematics are available from sources like Radio shack,
which also sells the components. These devices are limited to about one amp output in the
simplest forms but that is usually enough to recharge flashlight batteries, run radios, etc.
2. To run AC appliances while the generator is operating.
Unless you can store enormous quantities of fuel with easy re-supply without budget restrictions,
the amount of time you can run your generator will be limited. Keeping a generator running
many hours a day usually is not cost effective, but using a generator occasionally to power high
power requirement devices such as power tools, a well pump, a freezer or refrigerator while also
charging batteries is a more practical use of a generator.
One method to conserve fuel and keep generator use to a minimum is to run the generator in the
morning when you awake. Then run it again around noon, again in the late afternoon, and the
fourth time just before you retire for the evening. With these four 30-60 minute runs, you could
keep the freezer cold, and have the central heat recover enough to keep the house relatively
warm between generator runs. You could charge batteries to provide light.
STORING POWER FOR LATER USE WITH A BATTERY
While car batteries can be used in an emergency, deep cycle type batteries are best for our
emergency use, as they are designed to be discharged and recharged regularly without severe
degradation of the battery. Deep cycle batteries are used in boats, campers, golf carts, and many
other applications where the battery will be drained considerably before the next charge. They
are sometimes called marine batteries.
Starting batteries, like those found in cars, are designed more for providing high current output
for very limited time when you are starting an engine and are not designed to be allowed to
discharge very low below their charged state. "Cold cranking amps", a figure often quoted in
battery advertisements, is a measure of power a starting type battery can provide for a short burst
to start an engine and is basically a useless number for alternative power purposes. For
alternative power requirements, we are more interested in how many amp-hours the battery is
rated for, not how many amps it can deliver for a short burst like for cranking an engine.
Our concern is to pull relatively low current for long periods of time for alternative power
requirements. This is just the opposite as the needs of a motor vehicle battery which pulls heavy
current to start the engine for very short periods only. Once a vehicle engine starts, the battery in
a vehicle is essentially not used because the alternator takes over electrical power requirements
allowing the battery to recharge for the next starting requirement. That is why car batteries are
called starting batteries. Boats sometimes use a starting battery with deep-cycle capabilities.
These are called dual purpose batteries and will provide exceptional service in deep-cycle
applications. If all you have, however, are starting batteries, use them -- but monitor carefully
their discharge rate and recharge them before it gets too low (if you are using an invertor, it will
often sound an alarm when it is time to recharge.) Even batteries designed for alternative power
eventually fail, and so frequent recharging is a good idea with them too.
With batteries, amps-hours are important. Amp-hours are like gallons of fuel in a fuel tank.
More amp hours equals more power.
Size the battery bank generously, as no component of the system should be asked to
provide maximum output all day every day. Two batteries may be enough to run your lights, but
to keep a freezer going or run some power tools, a bank of six or more may be necessary.
Regardless of the number of batteries you use, it is the amp-hour rating that is most critical to us.
One large group 8D type battery may supply 220 amp-hours with only one battery. A group 24
battery, the size found in many cars, may only supply 85 amp-hours with one battery. Regardless
of how many batteries of what ever size you choose, remember that more is better. The deeper
you cycle your batteries between charges, the shorter the expected life of the batteries. This is
especially true with starting batteries but also true with deep cycle batteries to a lesser degree.
Storage batteries come in different sizes and capacities. When you price batteries for making up
a battery bank, you might want to look at the Amp-hours per dollar, other factors being equal.
Some deep cycle batteries are waterless, and require no maintenance. These usually cost more
and offer less additional benefit to us for alternative power storage than they would benefit a boat
owner who would possibly have more problems with a vented conventional battery in boat
Some deep cycle batteries have less amp-hour capacity for a given size but their price is much
less than the premium grade batteries in the same size. A 100 amp-hour battery at $50 may be a
better deal for our needs than a similar sized battery with 110 amp-hour rating for $60. In a
fishing boat where space is limited, the premium battery may be the way to go, but if you have a
lot of room in your basement for a lot of batteries, going for more "bang for the buck" may make
more sense regardless of size considerations for the amp-hour differences.
You can expand your power storage by using more than one battery. By linking the batteries
together in different ways, you can accomplish different goals.
1. Parallel, positive to positive, negative to negative, which multiplies the amp hours, that is,
the time you can use the battery before recharging. Ten 12 volt batteries connected in
parallel (positive to positive and negative to negative) would still supply 12 volts, but the
time before they would need tobe recharged would be 10 times longer than a single
battery. Most systems will use a parallel arrangement if the batteries are already of the
voltage that you want to use.
2. Series, negative to positive, which increases the output voltage. For example, ten 12
volt batteries would supply 120 volts if connected in series, ten times the volts of one
Batteries require maintenance, and preventing corrosion is high on the list. Apply a battery post
anti-corrosive compound to the terminals. These products can be found in any automotive parts
supply house. You can spend money for something specially formulated for this, or you can use
ordinary petroleum jelly. Either is better than nothing.
Batteries benefit from being protected from extreme temperatures. If this isn't possible,
you will need a larger battery bank to compensate for the loss of capacity. Batteries in heat have
a shorter life span and batteries in extreme cold will not produce their rated outputs. Keep them
at a full charge to prevent internal sulfating. A low voltage disconnect will prevent your
batteries from losing capacity and reduced life expectancy that results from discharging the
battery to exhaustion. Some invertors have this feature built-in.
The hands-down winner for battery choice is the deep-cycle marine battery, but that
shouldn't prevent anybody from using a car battery in an emergency. A car battery, plus a small
invertor (200 or 300 watts, costing less than a hundred dollars), could run small applications or
some lights. A brake light bulb plus a car battery can make an amazing amount of light in a dark
When making your battery list, don't forget the smaller batteries: AAA, AA, C, D.
Buy good quality rechargeable batteries, and maintain them properly. The C. Crane Company
has a great set of free recommendations, even if you buy elsewhere, get their literature. For
less than twenty dollars you can get solar battery chargers that work well with these smaller
People have used Ni-Cad rechargeable batteries for years. These work fairly well but had a
reputation for a short shelf-life and a "memory." They would lose their charge sitting for only a
few weeks between charges and the "memory" was that unless you fully discharged them
between charges, they had a tendency to produce a useful life of only the amount of charge you
had previously used them to before recharging them. Because of these two limitations, and
because the Ni-Cad batteries had a low amp-hour rating compared to a alkaline type battery,
many people were disappointed with Ni-Cads.
Now there is a rechargeable alkaline type battery with the benefits of alkaline but with recharge
capabilities. These are offered by Rayovac and are supposed to be recharged with the Rayovac
rechargers because they could leak or be damaged if charged with too much current. The small
solar chargers will not recharge these new type rechargeable batteries as fast as the Rayovac 120
volt chargers but the solar chargers will work without damaging the batteries. Because the little
solar battery chargers have such a small current output, they are safe to use if 120 volts is
unavailable for the regular charger.