Matching Batteries

[LByers]

I have two banks. Is it important that they match? The two house batteries are deep cycle no maintenance and the starter battery is a wet cell non-deep cycle. Will this create a problem when charging? Recently the house bank died and the starter battery tested fine. The deep -cycles are five years old and the starter an undetermined age.
Thanks for your help.

[ranger58sb]

It can matter, but it depends. Usually batteries within a bank should be (brand/model/age/chemistry/size/voltage) matched, and then sometimes you have some flexibility across multiple banks.


If by "no maintenance" you mean gel or AGM and the starter is flooded lead-acid (FLA), you may already have a mismatch. OTOH, some chargers are OK with charging AGMs and FLAs on the same setting, even if the charging voltages aren't optimum for each different style.


Anyway, a good place to start is with your charger manual. It may also suggest the size of each of the multiple banks should be roughly equivalent.


Depends.


-Chris

[edmundsteele]

The starter typically doesn’t get used as much as the house batteries and in your situation, if your charger is set up for AGM’s and there is no option for the auxiliary output to the starter battery to be set for lead-acid, you could just add a diode at the starter battery terminal, inline with the cable from the charger. Diodes are dirt cheap and will drop the voltage to your starter battery by 0.7 volts, preventing it from overcharging. Just make sure you put the diode in the right way round!
Ed