I have a bank of 18650 cells in 14 banks of 5 x NESE holders capabable of being fitted with 5 cells in parallel and a 14S BMS in my modified Rockhopper.
I have been plagued with individual banks failing with the cells going below 2V like 0.07 would you believe.
Upon testing I found one of the group of cells had shorted and the others the the CID had operated.
This is about the 4th occurance of this fault.
So it appears to me one cell is failing under load shorting out and then taking out the cells in parallel with it ? sounds very odd!!
After replacing the defective cells I bought morecells from Lan Plus in Melb.
I disected the battery pack and charged each bank up to 4.2 volts to ensure they were all balanced, I reassembled the pack and went for another test ride but about half way around a known circuit the Green Orange Red battery indicator on the handle bars showed red, very odd I thought and expected the BMS to cut the power and making me pedal home. hower this was not the case and I returned home under power however coasting when possible.
Upon checking the banks again I find yet a different bank had failed this time.
Removing the cells only this time I fitted them to my XTAR 4 without doing any mechanical work on the CID and tried to charge them, sure enough they began charging but showed NiMH cells (possibly due to the excessivly low voltage again.
After some monitoring over the weekend I was able to fully recover them the XTAR recognised them as Li and recharged to their 4.2V
All very odd I must say, so I discharged each one and recharged them to measure the individual capacities with my IMAX they came up around 23 24 K mAh.
So I checked the LG spec sheets to find out how they actually load tested them to obtain a high discharge of 20 amps.
Could not find any test data, so does anybody have any knowledge on how the cells are load tested to determing if they can actually produce 20A current?
Currenly I can load test them at 5 Amps and they seem to handle that OK.
My current understanding of these cells is if they go undervoltage the iR increases not reduces or in fact shorts?
