Right, so long as I have the same BMS cables to the same modules, I should be fine?
I'm going to keep the modules wired up in series, as per the original Leaf pack. But I don't see exactly how to keep the same order of modules if I make them into one stack?
What am I missing?
As long as you keep both
the BMS connections to the same modules and
wire the power wires to the same modules, then everything will continue to work.
When you split a stack of modules, simple replace the short copper bus bar with a heavy copper insulated wire with lugs to go under the M6 bolts of the replaced bus bar.
If you bring stacks together with their connection points facing (where there used to be a wire connecting the two stacks) then you can re-introduce a bus bar.
Do make sure you keep the same order electrically
(in wiring) even if yo ucompletely re-shuffle them mechanically.
For my electric truck (US Electricar S10) I converted one of the two "quart" packs from 2+2+4+4 into 3x4high by "folding" a 2-stack on top of the other 2-stack (and cut off one position of the base mounting plate) and converted the remaining quart and the half pack into 4 stacks of 9 high, because that was the most economical filling of the existing battery box. So, I split the stack of 24 modules in 9+9+6 and re-arranged the 2+2+4+4 into the remaining 3+9. I split the bus bars and the "sensing" wiring for the BMS, keeping all sections wired in the same order and am using the original Leaf BMS with 12V continuous power for balancing and switched power for the CAN bus, which is connected to an ELM327 for reading with LeafSpy in "BMS only" mode.
For the order in the voltage of the pack, just follow the big orange wires and when you stand with the black dual contactor block closest to you (pack connectors towards you) then the wiring goes from the contactors to the left quarter pack, immediately behind the stiffening bar, this is the negative most contact; then from the contact nearest the relay block on the left quarter pack jumping across to the right quarter pack; then from the contact immediately behind the stiffening bar on the right quarter pack to the service disconnect (which includes a fuse) and which is the mid pack voltage and from there to the right contact on the halfpack; then from the left contact on the halfpack back to the relay block, this is the positive most contact at about 380V higher than the negative contact. Each quarter pack delivers about 95V (12 times 4+4V) and the 24 stack halfpack delivers about 190V. Hope this helps.