Q: Someone told me that you don’t need a BMS.
A: Below on the left is a picture from one of our customers that wasn’t using a BMS. It was over-charged,
which creates gasses, and can cause the outer case to bulge (this kills the battery). One of the jobs of a BMS
is to prevent overcharging. We’ve also seen batteries that have been discharged down to zero volts,
rendering them useless, but the photographs are not as interesting.
Even if you think you can’t over-charge because your smart charger stops at 13.8, unbalanced cells can and
will over-charge a single-cell, long before the overall pack voltage tops out at 13.8.
In conclusion, always use a BMS with lithium batteries.
Q: I fully charged my cells to 3.6 each and overnight they discharged down to 3.4v OMG WTF how am i losing
so much power AHHHH
A. This doesn’t necessarily indicate self discharge. LiFePO4 chemistry just takes some time to equalize. This
is normal.
Q: Someone told me that bottom-balancing is better than top-balancing.
A: Always top-balance. Will Prowse explains why in this informative video. Also, see Appendix C, About Cell
Balancing.
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