Cell balancing voltage ... ??

Zbugsii

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I am only planning to have my cells go up to 3.375 v. So I am top balancing them to this voltage. My question is... is this an acceptable practice? Or should I go to a higher voltage?

Are there pros and cons to balancing at a lower voltage?

If I am going to set my BMS to a max cell voltage of 3.375, can I balance them to this voltage or go some amount higher?
 

Bob B

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In most cases you would want to be at least to 3.4 volts ..... that is the default setting for most BMS before they start balancing.

You want to be well into the upper knee ..... I'm not sure if the knee has started at 3.375.

I would want to balance at 3.65 / .... or at least 3.5 per cell even if you won't be charging that high.
 
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Dzl

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I am only planning to have my cells go up to 3.375 v. So I am top balancing them to this voltage. My question is... is this an acceptable practice? Or should I go to a higher voltage?

Are there pros and cons to balancing at a lower voltage?

If I am going to set my BMS to a max cell voltage of 3.375, can I balance them to this voltage or go some amount higher?
You should go to a higher voltage. Differences in voltage at this low voltage will not be very pronounced, (i.e. small differences in voltage can equate to big differences in SOC in the middle of the voltage range). So as @Bob B mentioned, even if you will be keeping your cells at/under 3.375v, if you top balance, it would be best at or above 3.50V at the minimum, maybe 3.55V.
 

Zbugsii

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Thank you for the replies.... this confirms what I was thinking... that I should go to a higher voltage.
 

noenegdod

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Personal opinion:

Top balance to 3.6ish. Do that once. Reduce the max cell voltage to 3.375 for daily use and occasionally bump it back up to 3.6ish for one full charge and reduce it back down again for daily use.
 

time2roll

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3.375 BMS max is fine depending on your charging voltage. If you plan to charge to 13.50 (4s 3.375v) you will have frequent BMS cell over volt shut downs as the cells drift even a small amount out of balance. The BMS probably cannot keep the cells perfect. I would let the cells run higher to maybe 3.45 limit the battery to 13.6 or 13.8 and limit the charging to 13.5 volts. The BMS is to protect the cells if something goes wrong, not to be the primary limit on charging. Also need to set the balance to come on low enough to get some balance activity during charge.
 

DLTooley

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One thing I’ve noticed is an apparent substantial drop off in solar charging at lower voltages.

I haven’t measured it, but it seems I drop out of bulk way to early if I charge to 13.9 as opposed to 14.2.
 
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