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I have charged ~20 packs of 4S batteries and I noticed that cell connected to + on charge circuit almost always is the one who gets charged first (reaches full voltage). Is this a coincidence or is there an explanation for it?

Would the same apply for discharge too?

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    \$\begingroup\$ If all things are equal, then it is a coincidence Battery temperature may perhaps make a difference. \$\endgroup\$
    – ATCSVOL
    Sep 26, 2022 at 6:38
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    \$\begingroup\$ The balancing/sensing circuitry on the charger may not be calibrated the same for all cells. \$\endgroup\$
    – HandyHowie
    Sep 26, 2022 at 6:48
  • \$\begingroup\$ Hard to say for sure. Bad BMS design? Please post a schematic. \$\endgroup\$
    – winny
    Sep 26, 2022 at 8:56
  • \$\begingroup\$ I have noticed this, too, but in the discharging of dry cells in a lantern battery, especially with any slow discharge. You should be commended, as you are very observant, and I find that is rare, and a precious quality to possess. I call this effect charge migration. \$\endgroup\$ Oct 28, 2023 at 15:13
  • \$\begingroup\$ How fast were you charging? Separately, or together? Using your bench power supply? Were the cells subject to ripple from a SMPS -- if so, how much? To catch this elusive effect, please record as many details as you can (preferably in your question). Please be diligent and careful to answer all of my questions, so that we at EESE may best help you. \$\endgroup\$ Oct 28, 2023 at 17:08

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