Cheap BMS solution for a 96S pack (32 3s4p LGChem Modules)

Topics concerning OEM and open source BMSes
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Jacobsmess
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Cheap BMS solution for a 96S pack (32 3s4p LGChem Modules)

Post by Jacobsmess »

So, I am going to build a 32 module pack consisting of 3s4p lg chem I-Pace modules but I'm struggling to find a solution for BMS to keep costs down.

If possible I'd like to reuse the existing slave setups (as I'll already have them) but need to work out how to control them. The modules each have taps for each series of cells and 2 temp sensors that connect to the slave BMS boards. I'm sure EVS-BMS is a way of achieving this but currently it does not support the I-Pace slaves and I'm not sure how I'd go about reverse engineering them....

Presuming they were to connect via canbus, is it as simple as providing power to the original BMS and using an Arduino setup to read messages? Thanks
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Re: Cheap BMS solution for a 96S pack (32 3s4p LGChem Modules)

Post by Alibro »

I can't help with your question but have a VW eGolf battery pack with 2 additional modules to bring it up to 96S so the VW BMS is no use to me. I decided to try a Nissan Leaf BMS to see if it would work and so far it seems to. I have only tested it briefly but was able to see all the cell voltages on LeafSpy.
However after watching Johannes latest video I'm not sure it will work for me but I'm going to give it a try.
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Re: Cheap BMS solution for a 96S pack (32 3s4p LGChem Modules)

Post by Jacobsmess »

From Johannes latest video he was talking about his own BMS not the leaf one, but this is really helpful information, I'll investigate the leaf BMS, do you know the voltages is expects on all the channels? How easy does it integrate into other charging and control units?
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Re: Cheap BMS solution for a 96S pack (32 3s4p LGChem Modules)

Post by johu »

Well I wasn't but Janosch was ;) The Leaf BMS (at least the 40 kWh one) doesn't like its wires extended as is done with packs split between front and rear.
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Re: Cheap BMS solution for a 96S pack (32 3s4p LGChem Modules)

Post by Jacobsmess »

johu wrote: Thu May 04, 2023 11:16 am Well I wasn't but Janosch was ;) The Leaf BMS (at least the 40 kWh one) doesn't like its wires extended as is done with packs split between front and rear.
That's a shame, is there any workaround or do you have an idea of a suitable alternative for my purposes?
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Re: Cheap BMS solution for a 96S pack (32 3s4p LGChem Modules)

Post by Alibro »

johu wrote: Thu May 04, 2023 11:16 am Well I wasn't but Janosch was ;) The Leaf BMS (at least the 40 kWh one) doesn't like its wires extended as is done with packs split between front and rear.
This is why I was asking about using microphone multicore as it is very well shielded. If the issue is more to do with length of cable then it won't help of course.
The Leaf BMS I have is a 24kW one so might not be able to do much by way of balancing but at least it will let me monitor cell voltages using LeafSpy.
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Re: Cheap BMS solution for a 96S pack (32 3s4p LGChem Modules)

Post by joeflickers »

Alibro wrote: Thu May 04, 2023 1:09 pm This is why I was asking about using microphone multicore as it is very well shielded. If the issue is more to do with length of cable then it won't help of course.
The Leaf BMS I have is a 24kW one so might not be able to do much by way of balancing but at least it will let me monitor cell voltages using LeafSpy.
Interesting,
I also have the 24kwh leaf bms from a salvaged leaf pack but im making a cutom pack,are you able to monitor current output and command contactor on off using the leafspy and the leaf bms?
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Re: Cheap BMS solution for a 96S pack (32 3s4p LGChem Modules)

Post by Alibro »

joeflickers wrote: Sun May 14, 2023 6:44 am Interesting,
I also have the 24kwh leaf bms from a salvaged leaf pack but im making a cutom pack,are you able to monitor current output and command contactor on off using the leafspy and the leaf bms?
I haven't tried, I'll be using a shunt to monitor voltage and current so Leafspy will only be for monitoring purposes.
I don't know how much the BMS will be able to balance the pack but at least I should be able to see if a cell is too high or low.
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