Balancing

[cmysstailights]

Are my cells out a lot or are they within spec. 99 ds 7 leaf pack zeva bms. Charger is set to 10amps at 57.4volts.

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[Sergio]

It looks like the charger may not be charging to 57.4v (4.1vpc).

Charge the pack until is fully charged, measure the voltage and divide it by 14 to get the VoltsPerCell.

Whatever that number is round it up to 2 decimal places and set your "Balance Voltage" to that calculated number.

[cmysstailights]

Originally Posted by Sergio

It looks like the charger may not be charging to 57.4v (4.1vpc).

Charge the pack until is fully charged, measure the voltage and divide it by 14 to get the VoltsPerCell.

Whatever that number is round it up to 2 decimal places and set your "Balance Voltage" to that calculated number.

Ill check when its done. I set the pot with a volt meter. Its a chinese charger. I will double check voltage.

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[cmysstailights]

I just re adjusted the charger to 57.4 when i put my meter on dc amps it shows 29.78. But zeva shows .8

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[cmysstailights]

Got the amps to 11.4. Had the meter set wrong . 57.3 v 11.4a


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[cmysstailights]

I reached out to ian from zeva and here is his reply.

My question
Zeva bms on 7 leaf pack.* I keep hitting a high cell.* How does the bms balance work?* Will it still balance when stopped (attached pic)?* When it hits the high cell will it still balance.* Charger set to 58.0v 10amps.* Bms settings 14 cells, min volt 3.0, max volt 4.15, balance 4.14, hysteresis .02, stationary mode yes.**


His reply
Hi Andrew,

Yes, it will keep doing balancing even if a high cell has tripped the LV relay output. Looks like you have about 0.07V imbalance at present which isn’t too bad, but the BMS will be able to improve that over time.

58V max from the charger gives 4.143V average, so with the trip voltage set to 4.15V you only have 0.007V tolerance for imbalance between cells (assuming the charger’s output voltage is accurate - might not be exact), which is quite tight. I’d probably recommend bumping up the Max Volt to say 4.20V to give it a bit more margin. This is still a safe voltage limit for Leaf cells, and should prevent these BMS trips. Once the BMS has had some time to improve battery balance you may be able to reduce it again, though there’s no real harm having a larger BMS tolerance for imbalance if you’re not charging to the upper limit of 4.20V/cell.

Any particular reason you’re using a fixed balance threshold? Usually I’d recommend leaving it on Dynamic so that the balancers can be working more of the time (whenever they detect an imbalance, rather than only at the end of a full charge).

Kind regards,

Ian Hooper

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