Make Your Own Emergency Power Plant

If you have a car, a moderate tool collection and good tinkering abilities, you can make your own emergency power plant.

| January/February 1985

If you're anything like the folks here at MOTHER'S Eco-Village, you're probably swamped with nagging little chores that require some drilling here, some grinding there and a bit of cutting somewhere else. Trouble is, all these work sites somehow manage to be nowhere near a source of 110-volt power — so, unless you're particularly fond of hand-tool labor, you've got to either spring for a portable generator or resign yourself to a ramshackle existence.

Curiously enough, nearly everybody owns — and uses most every day — a reliable and generous source of electrical energy without even knowing it: the modern automobile! Yep, if you drive a car or truck manufactured between the middle 1960s and the present, it's possible to modify that machine's charging circuit to make it deliver 110 volts of 20-amp (or greater) DC service at the flick of a switch. With that amount of power, you'd be able to run lights, power tools, pumps, resistance-element appliances or just about anything that doesn't use an induction (AC only) motor or a transformer. Here's what you need to know to build your own emergency power plant.

"Alternative" Energy

Around 1963, you see, the major auto manufacturers started to equip their products with alternators, which not only made the cars more reliable, but opened up a whole world of possibilities to tinker-types like us.

Actually, the design of an alternator is somewhat opposite to that of a generator: Rather than current being extracted from an armature rotating within a wound stationary field, an alternator's output is drawn from three stator coils fixed around a spinning multipole rotor containing the field windings. This produces high-frequency AC current, which is then rectified, through diodes, into the direct current used in automotive charging systems.

Now, since an alternator's output voltage increases as its rotor RPM is boosted, a regulator is included in the system to sample that output and compare it to a desired reference provided by a Zener diode. If the output is too great (or too little), a transistorized circuit controlled by the Zener adjusts current flow to the field rotor to keep the alternator's output voltage within acceptable limits (between 12.5 and 13.5 volts).

Two Simple Circuits

All that's fine, of course, for charging car batteries, but we wanted to move on to bigger and better things, so we turned researchers Dennis Burkholder and Robyn Bryan loose on a staffer's 1978 Ford pickup to see if they couldn't coax it into giving up 110 big ones without damaging the stock equipment. What they came up with is a pretty ingenious use of about 50 dollars worth of over-the-counter and junkyard parts, a hookup that comes close to duplicating the convenience and performance of commercial converters that are considerably more expensive!

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