Oh my!
I think you meant to say 3.4V.
Kindly name this presenter. Thanks
To conclude - if you're cells are close (58mv max difference in you're example) and do not affect you're desired hi / low operating voltage range and they stay that way day after day - then I wouldn't worry too much and just monitor to make sure you're BMS keeps them within what you need.
I am studying to better understand the voltage deviations in brand new EVE LF280k v3 cells I purchased from Docan in Texas. They were promoted as Grade A cells. I recently put a 48 v battery bank together, top balanced, and really liked the 0.004 v diff spread of 15 out of 16 cells while testing Discharge down to 20% soc, then Charging @ 30 amps back up to full. I did NOT Like seeing one cell acting oddly, and thinking of that one cell as a Faulty Grade A Cell, while wondering if maybe it might be viewed as acceptable to Docan if it still can put out 280 ahs. ... Here's from my notes on that one cell: On Discharge, @ 58% soc on my JK BMS, this one cell was @ .068v diff below the other 15 cells that all remained at 0.004 v or less diff throughout my discharge and charge testing. At 22% soc, that one off cell reached .119v diff lower than all the others during a -68 amp draw. That seemed alarming to me. Then on a 30 amp Charge up to full, my notes show a .053 diff above all the other cells (a spike) at 53.98 battery voltage heading to 100% and
Thank you Steve S. I have really learned allot from your postings. I have used Docan Battery based in China w a warehouse in Texas for 6 days shipping time in tracked well packaged boxes to my home in California. The puzzling response I got back from Jenny Wu at Docan (sales person handling my purchase) after my initial email about having an issue was this (exact quote ): "This is because there is voltage difference between this cell and others. You only need to discharge each cells to 2.7V, and then charge them together to 3.65V". ... My First Thoughts were: How Could that fix the voltage diff swings I do not like or want in a new battery cell. I could try that idea on my one problem cell and mix it in to a 24v battery bank I just top balanced, that I am assembling and testing next: I would do a second top balance too, for testing w all with same LF280k v3 chemistry. Got to say that Jenny Wu Docan response seems like a time suck idea. .. I am wondering what 0.xxx volt diffs (aside from spiking that prevents full charge) might qualify at Docan for a cell return, and replacement. ... I will ask to see if I can get a straight response.
I did not yet read the EVE spec sheet for LF280K v3. .. but have recently read outside this forum via questions to Google AI, that cycling brand new LiFePO4 Prismatic cells down to bottom voltage, and then charging back up to full, 2 or 3 times is a way to activate it's cell chemistry, plus help em last longer and perform better after that. While, I have not yet read that theme in this forum, I wonder if that has been discussed. I have heard stories from a fav member in this thread about his reviving some messed up drained and freeze exposed LiFePO4 cells by draining em down to bottom soc, and charging back up to full at 30 amps; which is similar to what Jenny Wu at Docan has told me to do for my one brand new misbehaving LF280K cell : : getting 0.050 v to 0.120v diff in discharge to 20% soc, and 0.040 to 0.055v diff when charging back 100% soc with 2 amp balancing activated at top. I have decided to test Jenny Wu of Docan directions on just one cell, and mix it in with a 24v battery of the same new cells I have here, and building next. I want to see how my messed up cell behaves after that. While I think it will most likely be a waste of my time, I am interested to see if it makes any difference. Also, since I am heading to my Costa Rica hangout for a few months soon, I may not finish that test until a later date. Wondering if any LiFePO4 suppliers recommend what Jenny Wu of Docan told me (draining down to 2.7 volts, then charge to full) ? ... In some ways I am still a newbie learning more all the time ;+) I just have 6 .. . DIY LiFePO4 Battery Banks under my belt: one 12v, three 24v, two 48v, and cells w JK BMS for my 7th build :+)
