dual batteries

[Pioneer]

Has anyone installed a dual battery system with an isolator? What brand of isolator did you use and any difficulties you encountered?  do you need to upgrade the alternator?

Ken

[Red90]

Sure.  The traditional way was to use diode isolators and you can pick those up at any auto parts store.  The problem with them is they always drop the voltage and thus one or both batteries never gets the full alternator voltage and then does not ever fully charge.

The better solution is to join them with a solenoid.  You can power the solenoid a few ways.  You can have a manual switch.  You can use the alternator charge light wire to turn it on, so that it only connects when the alternator is working.  The way I have it on mine is to use a voltage sensing relay to turn on the solenoid.

This is the one on my truck: http://www.powerstream.com/battery-isolator.htm  It only turns the solenoid on when the voltage is high enough that the battery is charging.

There are two sort of main ways people setup the batteries...

1) The way I do it.  One battery is only connected to the starter.  Everything else  including the alternator is connected to the other battery.

2) One battery is connected to all of the original equipment in the car.  The second is connected to accessories that you use when the car is not running.  This the the "normal" way if you had a camper or trailer or whatever.

[headdamage]

The third way is to wire both batteries together in parallel.