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Series of Parallel Packs Battery Cells Balancing

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Manoni_Lo

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Hello,

I have to simulate a BMS of a Li-Ion Battery. It is formed by 8 packs, each made by 6 cells connected in parallel, all connected in series.

I've read something about balancing techniques, but all references i've found explain how to balance single cells connected in series, as parallel resistor technique or active methods. They seem to me not to work to balance parallel cells since you cannot control single cells SoC, but you can only decide to remove charge from an entire pack.

How can I fix this problem? Tell me if I am wrong with something.

Thank you for reply.

Lorenzo
 

std_match

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A "pack" of parallel cells are internally balanced automatically since all cells have the same voltage.
So you only need balancing between the series-connected packs.
You can just view the battery as 8 series-connected high-capacity cells.
 

Manoni_Lo

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Ok,

of course voltage is the same. But according to simulations SoCs are not. This is exactly the problem I have to solve.
Here's a picture of the simulated SoCs of 48 cells.

SoC.png

The battery is taken from this article. I have run the same simulations performed here:
"Lithium-ion Battery Electrothermal Model, Parameter
Estimation, and Simulation Environment
Simone Orcioni, Luca Buccolini, Adriana Ricci and Massimo Conti"
 

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Are you aware of any existing BMS that balances parallel connected cells individually? I'm not.

If you feel that it should be implemented though, consider a possible circuit topology, estimate the effort and expectable benefit.
 

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