Yes, you can actually be discharging your battery if the total current load
exceeds the output of your alternator, but it's pretty rare that you'd draw
the battery all of the way down. I've seen cars that after a long night trip
through West Texas running brights and high wattage driving lights that
showed a healthy charge rate for an extended period the next day, but they
didn't totally drain the battery. I don't think the cooling fan's going to
draw more than a couple of amps and unless you're running a couple of high
power amplifiers on you stereo, the stereo shouldn't draw much either.
Auto batteries are not really designed for repeated deep discharge/charge
cycles like some marine and other deep cycle batteries. They like to be
charged back up immediately after being used to start the car. I'm not sure
what the differences in design and construction are between the two types,
but there is a difference.
As Pat suggested check all of you connections. I like to use serrated star
washers and a bit of petroleum jelly on grounds to the body, and frame too
since we're talking separate items on the roadster.
After you know all of your connections, both positive and grounds, are clean
and tight, then you'll have a better idea of if you need a new and/or higher
output alternator.
HTH, Ron
>Pat:
> Sounds like your alternator is not putting out enough voltage. The
> voltage should be around 13.6 volts. You could have a bad regulator
> or alternator, or a bad connection with either of them.
>
> Check to be sure that there is a ground strap between the engine and
> frame/body. The alternator is grounded to the engine and the regulator
> is grounded to the inner fender. If they are not at the same potential
> it can cause problems.
>
> Are you running a stock alternator?
>> Adam:
>> I've been putting some miles on my car since the water pump/electric
>> fan/head gasket/etc. replacement and have found that after long drives
>> with stereo, electric fan and headlights on the battery is nearly dead.
>> It is a new battery and this did not happen before the electric fan.
>>
>> I'm not an electronics guy. I have a multi-meter and it says that with
>> everything BUT headlights on (fan is on) I have about 12.10 volts at
>> the battery. If I turn the headlights on it falls to 11.70 or so.
>> Does this mean I'm draining my battery faster than I can charge it?
>>
>> Or, if I'm doing it wrong, can I use a multi-meter to test this, and
>> what do I do?
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