Solar Battery Bank Balance (Discharge 1 bank)

Hi Tom George

I have had to place my batteries as is due to space being a factor..

The two banks of (6x 12v batteries) are wired with thick heavy heavy duty welding wire

The two banks sit side by side I've only got 1 wire linking the two banks
I might make additional wire and make it as if battery 1 on bank A and B are connected and battery 6 on bank A and B are connected.
Essentially what you have drawn above..

Anyways. I don't want to spend money on batteries and batteries would be 3 yr old or so.

I just want to build the kit.

So can I get some assistance with coding.
I'd also like to know if Arduino would accept one of the analog inputs being a negative value

I will start researching other projects with similar Arduino uses and see what I need to do