In my attempt to find a photo to share I searched the web - boy, I am SO SURPRISED how many places just get it wrong, and how few (if any) really get it right... In fact, the 'Do it this way' photo I sent actually had it wrong.. ARG. So, rather then spend more time searching the piles-of-wrong, I made up this photo myself.
There are three key points in this photo:
- All the serial jumper wires (S) need to be the same size and length.
- All the paralleling jumper wires (P) need to be the same size and length, though the can be different than the serial jumper wires (S).
- The main feed wires are connected to opposite corners of the bank.
Extending this concept further, if there are two 'banks' of these series/parallel batteries, again make sure the connecting wires are the same length to each bank, ala:
Should add here: I am not a fan of placing several individual batteries in parallel, issues like the above just come up. I much prefer series connection of larger cells, ala replace the 12x - 6v T105 batteries above with 6x L16 form factor 2v cells all in series. One would get the same capacity, longer life, and eliminate all these paralleling issues.
But if you must (and I know there are physical space limitations that come into play here as well), the above is how I would suggest connecting the banks up.