>Isn't the amperage output of the alternator just as important or more
>important than the output voltage, as long as the voltage is higher than the
>battery voltage would be at full charge? If you've got quite a load on the
>battery, i.e. lights, heater or a/c, trying to charge an aux. battery, even
>if your voltage is close to 15 from the alternator, if your alternator
>amperage capacity is not enough, will an adjustable regulator really help?
>On my battery charger at home, it is adjustable between 10 and 30 amps, and
>the voltage fluctuates up to a little over 14. What's the real story with
>amperage versus voltage?

Well, the short answer is that volts should remain about the same all the
time. A good beginning analogy is to think of it as plumbing. Voltage is
like water pressure. Too much voltage will burn up sensitive electronic
devices just as too much pressure will bust fitting in the faucets and
valves. Your alternator needs to put out electricity at a higher voltage in
order to overcome the internal voltage of the battery. Amperage is
analogous to flow rate (e.g. gallons-per-minute). All the stuff hooked up
to the alternator will draw a certain amount of amperage. Just like having
too many showers running will cause your water pressure to drop, if that
total amperage draw is higher than your alternator can supply, the voltage
will drop. Of course, no amount of money will get you a voltage regulator
that'll prevent this drop. The "ampacity" of your alternator is the
deciding factor. Now as far as fancy voltage regulators, it might be
worthwhile if you've had trouble with the stock one built into the
alternator, but if you haven't had any trouble, why bother? Unless you're
seeing a big voltage drop between the alternator and the battery due to
resistance (analogous to water pressure loss due to friction in the pipe),
I can't imagine why you'd NEED to adjust your regulator. Even then, I'd put
in thicker gauge wire (bigger pipe) and check my return paths before I'd go
and crank up the voltage...