Pros and cons of 2 bateries?

["John G. Napoli" <john@xxxxxxxxx>]

Actually, no.  You need a larger alternator, and one that is capable of
generating more power at lower rpms probably, too.

The second battery will help until it begins to run flat, a half hour after
you install it.  You see, when the car is running the alternator supplies
100% of the electrical power needed.  Anything it can't produce is made up
from the battery.  Your alternator is not up to the task because of the
additional electrical accesories you've installed.  So the difference is
being supplied by your battery.  Two batteries will last longer, but if your
alternator can only produce, say, 80% of the power needed, the difference is
gotta come from somewhere.

Think of it like a paycheck and a bank account.  The alternator is your
paycheck, and the battery is your bank account.  If your expenses exceed
your paycheck, then you have to make up the difference by withdrawing from
your bank account.  A larger bank account (two batteries) will last longer,
but eventually will run out if the paycheck (your alternator) is not large
enough to cover your expenses (the total power required by all your
electrical devices).

So:  you need a larger paycheck (don't we all?).  You should look into a
larger alternator and a smaller alternator pulley.  But one battery should
suffice, unless you need to run your sound system for long periods of time
with the engine off.

John

> I need two batteries because my sound system is pulling current from other
> things in the car (head lights)
> KEVIN 71 IMP