How to design 8s9p 32700 lfp

[occuplus]

i wanna build 8s9p 32700 lfp pack
a-Should i fold 4s to 4s as attached picture? (i didn't add all paralels.)
b-Should i fold 5p on 4p ?
c-Does it matter B- B+ on inner sides or outer sides?

Thanks for help.

 

[Korishan]

a-Should i fold 4s to 4s as attached picture?

That's fine. Just make sure there is good protection between the layers. Probably a layer of fiber paper on each section being folded would be fine.

b-Should i fold 5p on 4p ?

I would think that with this arrangement it would be better to just go 8s10p, or 8s8p. Keep the design even and balanced for easy of assembly, maintenance, and security (putting in a box and/or shrink wrap, etc)

c-Does it matter B- B+ on inner sides or outer sides?

Not sure what you mean here. The terminals will alternate as the groups are added. Unless what you mean is if the terminal connections are on the folded sides, or are on the outside sides. I'm guessing it is this you mean.
For safety, I would say on the outside edges, or as your image shown top/bottom placement. This will keep the most powerful tabs from accidentally touching.
However, you could also put the connecting terminals on opposite sides of the inner connections. For example, the Pos could be on Row 1, and the Neg on Row 8. This would keep them far apart, but at least on the same level/plane of each other, making wiring up to something else a little easier. I would not put them any closer than 4 cells, though (ie 3 cells of separation)

 

[occuplus]

AI s answer. I ll fold on 4s. Is it correct?

"Short answer: Fold the pack in the middle of the 8S string (between S4 and S5), and keep all 9 cells of each parallel group together — don’t split 9P into 5+4.


Explanation and reasoning:

• Folding at the 8S midpoint (S4↔S5) gives a clean, symmetrical pack: you end up with two equal blocks (4S + 4S). That way your positive/negative busbars are shorter and more balanced, current paths are more even, and BMS balance leads are neater (B4/B5 become the central point).
• Splitting 9P into 5P + 4P might look easier for fitting, but it breaks the parallel symmetry. If the 9 cells of a group don’t share the same busbars, current distribution can become uneven, and that increases imbalance and safety risk. Ideally all 9 cells should sit under one common + and − bus.
• If physical constraints force you to stagger cells, then you must carefully equalize busbar lengths and connections, and ideally add fuse wires for each cell. But it’s more complex and less robust than keeping all 9P together.

Practical build tips:

1. Build each series group (S1…S8) as a single 9P block with one positive and one negative busbar.
2. Arrange S1–S4 on one side and S5–S8 on the opposite, folding at the middle (S4+ ↔ S5−).
3. Route the BMS balance leads in sequence (B0…B8), keeping them as short and tidy as possible.
4. Avoid crossing or long asymmetrical power leads — symmetry is key for even performance""