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Set BMS to actual capacity or rated capacity?

Freep

Solar Enthusiast
Joined
May 11, 2020
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435
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USA
I bought 40 315ah cells from Luyan and the testing sheet shows that the cells have a capacity of 333ah. When I set up the BMS should I set the capacity in the BMS to 315 or 333 or does it even matter?
 
I bought 40 315ah cells from Luyan and the testing sheet shows that the cells have a capacity of 333ah. When I set up the BMS should I set the capacity in the BMS to 315 or 333 or does it even matter?

It's purely your choice. If you set to rated, you know you have some left when you get to 0%, but not how much.

If you set to actual, you know how much you should have, but not if some degradation has occurred.

Personally, set to a little below tested (2-3%), and conduct yearly capacity tests to confirm and adjust.
 
I bought some of the same cells (they arrived today) that also tested out at 333ah
My plan was to set the BMS at 315ah for exactly the reason Eggo mentioned above.

Back in the summer I put together some Seplos kits that were set up for 280ah cells. The manufacturer settings were set at 290ah.
The cells used for the kits tested out at 312ah.
 

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