So the cells finally arrived, nearly three months after ordering.
We were 99.9999% they could not be 420ah (we did have our eyes open so please comment appropriately), but curiosity won.
The question was really: How (good or) bad are the cells?
Individual cells came out at:
So .... less than 60% of the stated capacity. Not good.
Although the voltages were "similar" upon delivery, clearly the SOC was wildly different. We started off with a 14.6v charge in series with BMS set to HVD at 3.65v. This lasted only around 5-6 hours (Amy's cells normally take around 10-12 hours). We then connected the cells in parallel and top balanced at 3.65v which took another 12 hours or so (Amy's cells usually take less than one hour) - suggesting the the SOC upon arrival had a very big delta. We had also weighed the cells and although I can't remember the exact weights there was around a 0.15kg delta which is huge.
All in all those cells are a fail and we shall of course be attempting a clawback of our money.
We have clear correspondence from them that every cell is a minimum of 420ah.
They are now back in series and being charged at 20a. I want to see what the delta looks like between the knees, and then to see how close (or far) they are at full SOC. After two hours the delta is 0.015 which is not too bad. Amy's are normally 0.00something
We were 99.9999% they could not be 420ah (we did have our eyes open so please comment appropriately), but curiosity won.
The question was really: How (good or) bad are the cells?
Individual cells came out at:
- 242ah
- 244ah
- 242ah
- 243ah
So .... less than 60% of the stated capacity. Not good.
Although the voltages were "similar" upon delivery, clearly the SOC was wildly different. We started off with a 14.6v charge in series with BMS set to HVD at 3.65v. This lasted only around 5-6 hours (Amy's cells normally take around 10-12 hours). We then connected the cells in parallel and top balanced at 3.65v which took another 12 hours or so (Amy's cells usually take less than one hour) - suggesting the the SOC upon arrival had a very big delta. We had also weighed the cells and although I can't remember the exact weights there was around a 0.15kg delta which is huge.
All in all those cells are a fail and we shall of course be attempting a clawback of our money.
We have clear correspondence from them that every cell is a minimum of 420ah.
They are now back in series and being charged at 20a. I want to see what the delta looks like between the knees, and then to see how close (or far) they are at full SOC. After two hours the delta is 0.015 which is not too bad. Amy's are normally 0.00something