Reagle wrote: ↑
Tue Aug 11, 2020 3:32 pm
Mine was done in April 2019. Same error, diagnosed very quickly as HV leakage to ground from one of the cells. Basically internal cell to case leakage. It takes a few days to diagnose as they had to take things apart quote a bit. You can dial it to the battery itself vs other systems in a few hours, but then you start dropping the pack and all that.. It took three weeks to get replacement parts, mainly since you can only ship cells ground from TN. Sofar so good, except my pack has never reached proper balancing on the new ones. They are always 60mv or so above the rest, and I feel it's affecting the range. I should do a full write up on this one of these days
Are they 60mv above at bottom, or at top? The new cells are likely large capacity than the rest. This means that their voltage swing should be *less* than the rest of the pack.
If you bottom balance, that means that the cells will match when the pack is discharged. But when the pack is charged, they'll have lower voltage than the rest, because the new cells have bigger capacity and aren't fully charged.
If you top balance, that means the cells will match when the pack is charged. But when the pack is discharged, they'll be higher voltage than the rest, because the new cells have bigger capacity and haven't fully discharged.
Neither of these states should affect range, as the cells will neither max out the charge or max out the discharge. However, if they didn't bottom or top balance, it's entirely possible that the cells are out of balance, which could affect range until the BMS adjusts over the course of months of driving/charging.
In short: a large mv difference will occur at various times if the cells don't have exactly matching capacity. If one or a few cells has lower capacity than the rest, this will affect range. If one or a few cells has more capacity than the rest, it won't affect range--provided they were balanced with the rest of the pack during installation.