Is it ok to hook up two batteries, in series, to a battery maintainer?

Question

I have a boat with two batteries. I can't seem to find a solar powered battery maintainer with 2 banks. Is it ok to hook both batteries in series with the maintainer? Or parallel? Or should I only use the maintainer on just one battery?

Answer 1

I would suggest getting two maintainers and charging separately. If you wire two batteries in parallel for maintenance, the stronger one will sink to the level of the weaker one.

Answer 2

Two 12v batteries in series is the same as one 24 volt battery, so don't ever hook a 12-volt charger up like that.



A solar maintainer, or any maintainer for that matter, isn't going to output enough in "maintain mode" for 2 batteries in a parallel connection.

Answer 3

I agree with everyone.

In series you'd need a 24V maintainer; a 12V one would either do nothing, if it has diode protection, or be damaged.

In parallel, the batteries would equalize so if one's discharged they would come to the same voltage; if they are in radically different states of charge enough current might flow to damage them, or melt the wire connecting them. If they are both in good condition and fully charged, it should be OK to put them in parallel and a single 12V maintainer will be safe, and better than nothing, even if they have different capacities. I run a starter battery and a house battery like that.

Answer 4

If 12 volt system connect +to+ Neg to Neg and U can charge both together if there the same amp hour. They make a isolator that will maintain both battery's with 1 charger.

Answer 5

Can do if the cables are set to parallel.



Just like jumping a car. The good car's alternator can charge the dead's car's battery.