Solar panel hook up with multiple batteries

[mitch]

I don't recall this being discussed anywhere.  If you have 2 twelve volt batteries connected in parallel so you're increasing the usable amp hours how do you connect your charge controller so that they are charged correctly? Connect both leads to one battery or one lead to one battery and the other to the second battery or something else entirely?  

Same question for 2 six volt batteries connected in series to give you 12 volts.

Thanks.

[david]

There is a lot of discussion in the boating world about the proper way to connect multiple batteries, to minimize voltage differences. The following considers this advice. I consider it mostly BS, but it is easy to do, so why not:

For two 12V batteries connected in parallel, connect the positive to one battery's positive terminal and the negative to the other battery's negative terminal. This way each battery has a jumper wire in the circuit which theoretically minimizes voltage differences.

One caveat: both batteries should be of the same type, ie both AGMs or both flooded cells. Don't mix the two.

For two GC batteries connected in series, connect the positive to one battery's positive and the negative to the other battery's negative.

David

[charliem]

For two GC batteries connected in series, connect the positive to one battery's positive and the negative to the other battery's negative.

David

[font size="3"]Not to be too nit picky, David, and I know you know this, but your instruction can be misinterpreted in the confusion of spaghetti hookups. I try to clarify by saying "for two GC batteries connected in series, connect the positive to the ungrounded battery's positive and the negative to the grounded battery's negative. Maybe just as confusing, but reversal causes smoke and I feel better   .
 [/font]

[admin]

Interesting that this comes up now. I was just having a similar discussion with a buddy about the 36V system we use on his bow fishing/flounder boat. That system has three banks of golf cart batteries in series. We draw on it with the 36V trolling motor, and two 500W inverters. The problem is that we know we are causing an imbalance in the overall battery bank. Further complicating things, we have multiple on board chargers that keep up with the high amp demands on the system.

My thought was to setup a bus bar to help equalize the load. Yet in my experience thus far on the boat I dont think a bus bar would have any real impact. We can clearly tell which bank of batteries is drawn on because they always sound the low voltage alarm first. Since this is the only time I've had to equalize more than two batteries I can only speak from this single experience, but I think the only true way to equalize a system is to keep the wiring runs as equal as possible. Then if you are feeling ambitious you should probably also consider rotating the batteries on a regular basis.

I know thats not exactly on topic but oh well...  

[mitch]

Thanks fellas.