Raisedeyebrows said:
While technically all of the Lithium cell chemistries are Li-Ion, many (most) batteries labelled one of those is not also labelled the other, as they are used as terms to distinguish specifcally between LiFePO4 and non-LiFePO4 chemistries.
So if it's labelled as both, you'd have to find the cell markings and see if any info comes up on those anywhere on the internet.
If it is indeed LiFePO4, then all the cells are overcharged, and the charger itself is either defective or is the wrong one for that pack. Also, the BMS is either the wrong one or is itself defective, allowing the cells to charge up that high.
It would not be the first pack shown on ES to have cells of one chemistry and a charger and/or BMS that are incorrect for the cells actually used in the pack. :/
The cells are rectangular, appear to be Lifepo4.
What markings on the individual cells show that they are LiFePO4?
Note that there are no external physical characteristics or appearances that can show you which chemistry a cell is. They can be any shape, size, connection / terminal type, color, etc.
The cells that were reading high did not seem to drop over the afternoon, I then plugged the multi-pin plug in carefully making sure it was connected properly,
Ah--well, if they're not plugged into the BMS, they won't drop because theyr'e not connected to the balancing resistors, which is what drains them to make them drop in voltage.
If they *did* drop without being connected to anything, then that would mean they're defective and self-discharging and would need to be replaced.
For some reason it seemed to have more power, climbed three very steep hills readily with no shut down (hmm?) .
Was it also left on the charger for a while prior to this (which would let the cells get more charge in them and perhaps balance a bit)?
If not, then I suspect there is a poor connection at that cell that read 0V, creating enough of a resistance that the BMS read taht cell as lower than it really was, and shutting off when under load. There could also be other connetions that were not very good, in that sense connector.
Could be caused by anything from a bit of oxidation on the contact surfaces, to contacts spread apart a tad too far, to bad crimps between wire and contact, to bad solder joints on the BMS board.
Thanks for your help AWolf, if you were anywhere near me I would gladly pay you to guide me through diagnosis and testing.
If you were close, I'd be happy to help without pay; it's good to help people and to keep ebikes on teh road (especially if they replace a car
).
Buuut...I do take contributions for experiments or doggie food, etc., at the link in my signature.