deep cycle battery selections

I am in the middle of piecing together a 12v battery bank, inverter and air compressor for a company work vehicle. The setup will consist of a voltage sensing relay to disconnect the battery bank when they alternator is not charging. A low voltage disconnect to disconnect the load from the battery bank when the battery's are discharged. 2000ish watt DC to ac inverter and a set of 12v air compressors.


I have always used 6v golf cart batteries for small solar installations. And had planned to use a pair in this project, but I may have an issue. With the solar setups, the max charge rate was about 20 amps per 2 batteries in series. When I put a pair in this truck, will I need to limit the charging current to the batteries? The truck has a 100+ amp alternator. If I'm thinking clearly, the batteries will only take as many amps as they need to charge. Or will they take as many amps as the Alternator can push into them?


Sorry for the lengthy post.
Any ideas or opinions are welcome.

Oh boy, where to start...

Can you use wet cells instead of AGMs? I strongly suspect wet cells will last far longer than AGMs in this case.

Use 12V batteries instead of 6V.

Batteries take whatever current they absorb. That is often far higher than what they "need" to recharge, AND often far higher than their warranty and specs allow.

Even though batteries should be current limited (especially AGMs), it is rare indeed to see any current limiting in automotive applications.

If you use the alternator charge light to control the isolating relay (instead of using a voltage sensing isolator) you'll reduce the impact of over-current into the batteries (and save lots of money!).


Don't discharge deep cycles deeper than 50% and if AGMs, recharge ASAP. (Batteries will last 3x longer if discharged 50% compared to 80%.)