Hey thanks for your input. I’m sure a lot of people have varied experiences. I must’ve met there probably differences between manufacturers. However that was not my experience. I bought Bestgo sales hundred amp hour. I did extensive testing before installing them in a vehicle. I put 40 for 100 amp our cells in a 1986 Toyota Celica. I charge them 3.65 V per cell or 160.6 V. After sitting for a while the voltage dropped 148.7 v or 3.38 volts per cell. I drove the vehicle every day for two years. There was never a variance at the end of charge. All the cells measured 3.38 V several hours after charging. I took the cells out of the vehicle And they said on the shelf for year and a half or so. I measure the voltage and they were all 3.38 V. However they do experience reversible capacity fade. I discharged all the cells and Got 45amp hours the first time. The second cycle I got around 65 amp hours and it continued to increase for five cycles. On the last cycle all the cells measured Close to 100 amp hours.
Sent from my iPhone On May 12, 2018, at 12:23 PM, Lee Hart via EV <[email protected]> wrote: >> From: Cor van de Water via EV <[email protected]> >> I also did tests on LiFePO4 cells and while self-discharge was low, I was >> able to prove from my measurements over many weeks, that there is was about >> a factor 2 difference in self-discharge current between the best and worst >> cell. Sample size was over 40 cells. > > This is what I have found as well. Brand new cells, all bought at the same > time from a quality source are very similar. Their amphour capacity, internal > resistance, and self-discharge rates are very close. > > But cells from cheap or low-quality sources have a much broader spread in > characteristics. Cells also get worse as they get old, or get cycled, or as > the temperature changes. Differences between cells accumulate over time, > getting worse and worse. You may get by without a BMS initially, but it gets > needed more as the differences between cells grows Not having a BMS means > shorter life. > >> This is exactly what the author of the quoted article found, that the >> capacity of the cells had not degraded, but the cells had gotten out of >> balance. > > Yes. The BMS was too primitive to do its job of balancing the cells. Only > having upper and lower voltage limits prevents against catastrophic failures; > but does not compensate for differences between cells. > > > -- > Excellence does not require perfection. -- Henry James > -- > Lee A. Hart http://www.sunrise-ev.com > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) > _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
