Expert: Cleggsan - 3/4/2010

Question
Hi, I have a 1998 Chevy Tahoe, and i am going to hook up a 3000 watt audio system to my truck. And I'm going to be putting 4 Optima batteries in the back, and i was wondering if my stock alternator would be able to handle that many wattage?

Answer
If you listen to low level classical or background music you will be fine. If you plan on turning up the volume to anywhere full level you will quickly drain the system and the alternator will become overloaded.

It is not a very good idea to put car batteries in parallel in the same vehicle without a special voltage regulator and charging system designed to handle mixed batteries.  The Optimas are deep charging batteries with low internal impedance which will do well when the subs start cranking up.  But they are for short term usage and when the sound energy goes on for a good long time the charging rates from the alternator will go up and the alternator may be overstressed.  Unfortunately, they don't all discharge at the same rate and with them in parallel the one with the lowest voltage gets all the charge and the alternator and the other batteries may go into a tizzy over it.  You are better off by replacing the one battery with a very high capacity one.  But, a high output alternator will be required either way, I must say.

PS:  Think about it:  3000 watts in a 12v system will require 250 amps!  If and when the batteries become discharged to the point the alternator must come to the rescue it may require more output than it is capable of giving.  A typical automotive alternator has an output of around 50 - 70 amps. Some trucks are more due to the lighting and other apparatus on them.  The Tahoe is probably around 70 amps maximum output - but I haven't looked it up; check your manual on it.