Yes, your numbers / thinking are good here. For wiring, 2AWG (33.6 mm2, chassis a = 181, transmission a = 94) would likely be adequate for short runs. Some like to go thicker - as in 1/0AWG (53.5mm2, chassis a = 245, transmission a = 150). I use this chart for my decisions -
https://www.powerstream.com/Wire_Size.htm Chassis a (very short runs) can handle a LOT more than Transmission a (longer runs - say 10, 20ft+)
Excellent pic/wiring-diagram - really help discussion and gives you something to check off when doing wiring!
> I could leave the existing series connections intact.
Yes I agree. Once you're in a position to put a load on the battery (or part of it) you can just pull the amps and touch the existing connections to see if they are warm/hot. As long as they stay warm->cool under max load, then that's all you need in my opinion.
>wondering if I can then use vertical bus bars to connect each of the cell groups - so bus bars for the red lines in my diagram
Sure - whatever works with hookup/easy-maintenance for the physical battery. For my inter-pack connections, I buy smaller copper pipe and flatten it, cut it into bars, and drill holes to use bolts to hook packs together. You just need the overall mm-squared (n the chart above) to carry the amps you need.
>wrap the bus bars in heat shrink tubing for safety
Again, great! Some use shrink-wrap. I use electrical tape - have gone thru 10-20 roles of it over 3 years. I really like to make sure + = RED and - = BLACK. So I'll wrap black wires 100% to make them RED if they are positives. In this way, the #1 rule - don't touch RED and BLACK except when hooking in series + to -
>would I be able to leave the existing copper busses that connect each 3-cell group to the next and use the existing module terminals, just connecting them via the appropriate gauge to a common bus bar
Again, sure. Me personally - I'm good with non-uniformity to leverage what's there as long as the connections are sound and maintainable.
For the hookup, this is what I'm picturing from the conversation... and if this is correct, then yes sir, you're right in the zone. It sounds like you have a firm handle on things, a good diagram for hookup, and thinking about things very well...
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