4@12v = 24v

Hi 2oldman,

Use the diagram smk provided (configuration #2). It is balanced. Yours are not.

Your first diagram can easily be made balanced by reversing the "feed" from either the positive side or the negative side. I'd be generous with the cable size on the interconnects and use the same size as the feed wires. Make sure all the interconnects are the same length.

Be sure to put the battery temperature sensor on a negative post.

Even though they are AGM batteries, after I tested the installation using a clamp on ammeter, I would spray them liberally with the GM anti-corrosion spray that Mex recommends.

Interesting. Contact resistance is much higher than the wire resistance in the amount of wire it takes to connect batteries. #2 wire has approx .016 per 100 ft. I bet in a typical battery installation where the connections haven't been serviced often the contact resistance can be .025 ohms or more. JMHO

I would avoid #2 as it takes five interconnects vs four.

The USB configuration also keeps the main cables closer together to avoid eddy currents from a high amperage loop. Same reason for keeping inverter cables tied together.

For more terminal space I would probably connect the solar & 24/12 converter to the opposite +&- from inverter.

either move the + or - to the other pair in the top example, you want an equal number / length of connects from the inverter pos to inverter neg on each pair of batteries. Or go with what smk posted (same thing). At least for the interconnects between the batteries go with something stupid large the cost difference is minimal - I am running #4/0 cables.

What smk posted.

I like the second for being more balanced, but why not run the loads on the first across both pairs instead of having an upstream and a downstream pair? ( I can't remember if you are a balancing believer or not. If not, never mind :) )

Another way is to have twin wires for pos and neg right from the inverter with one set to each pair. Those wires then power the inverter plus act as the parallel links so you don't need to parallel the pairs as well with more wires.

Where do you tap off your 12v and get your 12v ground to the frame for the 12v items that use the frame for neg to battery?

All interconnecting leads should be the same length, other than that it makes no difference.

Going with the first diagram. I think balanced would be to attach one main negative cable to the inner negative of one series pair and the main positive cable to the inner positive of the other series pair.