On Sat, Mar 13, 2021 at 9:30 PM Willie via EV <[email protected]> wrote: > I don't recall what Jack recommended about stopping the charge. Perhaps > depending on one or more cells reaching the upper single cell limit. > Basically it was to charge to 3.65Vpc and stop when the current dropped to 0.05C. That is what the specs sheet said which came with my made in November 2009 Thundersky LFP100AHA cells. Too many would miss, over and over again, that "stop at 0.05C" figure and over charge their cells. For my non-BMS 12V trolling batteries I bottom balance and set my charger to stop at 3.55Vpc and current has dropped to about 0.03C (I can't adjust the cutoff current so I adjust the max voltage). The resting open circuit voltage at 100%SOC of a LiFePO4 cell at room temperature is 3.38V so I just test the individual cells after resting for a while. In one of my 12V batteries, one cell gets to 3.78V just as the charge cuts off and it rests at 3.36V a couple of hours later so I know I'm not over charging them.
FWIW, in the Gizmo I had with buddy-paired 100AH LiFePO4 Thunderskys and 20 in series I top balanced them because my Zivan charger would not cut off at a current setpoint. I ran over 8 years without a cell level BMS installed and only a half-pack voltage monitor. When I sold the Gizmo I reinstalled the BMS boards since I didn't trust the new owner to be part of the BMS. After I sold it, there was one cell pair which started sagging below the rest so that one will either need to be removed or replaced. The new owner didn't understand the importance of the half-pack voltage difference needing to be close to zero. The BMS showed the issue. Unfortunately the owner rolled it on its side and hasn't driven it much for a while. If you don't know exactly what you are doing and understand the ramifications of it, then definitely get a quality robust BMS. -- David D. Nelson _______________________________________________ Address messages to [email protected] No other addresses in TO and CC fields UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/ LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org
