dear community,
there are several problems that needs advice.
firstly, our pack is using bq20z95 and recently we noticed some packs are showing either cell under-voltage or over-voltage issue. this makes the pack cannot be discharged when one of the cell reaches CUV first, or cannot be fully charged as one of the cell will reach COV. but cell balancing is enabled!
2. Some packs with this problem also shows the fuel gauging capacity at 0% and while trying to charge it up, we do notice the voltage rises across the cells but the SOC remains at 0%. In some packs, the relative and absolute state of charge are almost 80% apart.
3. a very dangerous situation, when the above packs are charged beyond its 1st & 2nd level protection (charge current, temperature) level, these protections did not kicks in. We have the pack charged at high current and the temperature reaches 75 deg C, but at its 60 deg C temperature threshold did not kicks in. But good working battery is able to demonstrate the 1st & 2nd level protections set are working properly.
4. Another problem that we notice is, the lifetime data. We did not see it updated when we try to simulate a higher discharge current than less recorded.
One problem at a time,
For 1 & 2, we're puzzled as Qmax is updating regularly and ImpedanceTrack is enabled as well. So why is cell balancing and fuel gauging not working. By the way, the batteries has cycle count less than 10 and they typically work within 30 deg C ambient temperature.
What could have caused these effects in the first place while most packs are working well?
thanks all.
John