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Discussion Starter · #1 ·
Hello All,

I have read EV West once offered a PCB to parallel the 16s LG Chem modules (linked below) at the cell level.


Does anyone have more information on these boards? A schematic, photo, or a link to the original listing would be excellent. Is it considered safe to connect cells like this? I believe they used the cell taps.

I am investigating doing similar with Renault Zoe modules (2p8s LG Chem) for my project.

Many thanks,

Tom
 

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Connecting the corresponding cell/groups of each sub-pack together at the 1S level

is an excellent idea for when those sub-packs are also "grouped", connected in parallel, at the bulk higher voltage level.

Conceptually, generically in principle, I know nothing about those specific packs.

This is much "tighter integration", allows them to more effectively stay balanced in real-time, distributing the shared loads more evenly, and one BMS can manage/protect multiple sub-packs acting as a single larger Ah capacity pack.

However, if the sub-packs are to be serially connected in "strings" at the bulk level to get to higher voltages (overall Ah capacity remains the same) then things get more complex and potentially dangerous. "Ground" isolation between the sub packs, how not only BMSs are wired not to mention outside circuits like chargers and loads are connected

that's all above my pay grade if you're talking about connecting the corresponding cell/groups of each sub-pack together at the 1S level in that context.

In either case, the sub packs need to all be factory fresh, or thoroughly tested as being equally healthy, and on an ongoing basis as wear levels increase over time

I would not do this with near-EoL scrapped packs bought second-hand

the need for protective circuit breakers or fuses complicate matters exponentially.

Those PCBs may have been taken off the market for good reason

parallel charging packs of fire-prone chemistries is a strategy fraught with high stakes danger even in ideal circumstances
 

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Discussion Starter · #3 ·
Thank you for your reply John. I think I understand the points you are making, sounds good.

In my case, I would be connecting modules (which are 2p8s cell configuration) in 3p4s configuration and connecting the cell tap wires from 3 parallel modules on the 1s level to give an overall pack that is effectively 6p32s. This would mean monitoring only 32 voltages, and prevents the difficulties of parallel strings.

I could charge simply from the top and balance/monitor normally as if the pack was built in 6p configuration. My concern is the current flowing through the tap wires, which perhaps could be addressed with fused or resistive connections, limiting charge rate or lower charged voltages. I would be interested if anyone has any thoughts on this.

The modules are used from a crash damaged 2017 Zoe but measure well matched. See attached photos of the modules.

I agree the PCB boards might have been removed for a reason, but EV West do still sell them if you ask so perhaps it is only due to them currently focusing on other battery types instead, rather than an issue with connecting modules in this way.

Thanks again for your reply,

Tom

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