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I have a 10S 36 - 42 V LIPO battery with all cells puffed due to prolonged not being used. I recharged the cells one by one 4.2V max under CC/CV conditions and they regained their normal format. The puffing disappeared. I would like to know more about the process that caused the puffing and return to normal. I can not find adequate info on the internet

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    \$\begingroup\$ How to you manage everyday tasks with such heavy balls of steel? I store my puffed cells outside in my designated hand grenade disposal bin. \$\endgroup\$
    – winny
    Commented Sep 21, 2021 at 13:43
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    \$\begingroup\$ @Winny I keep mine in my Chevy Bolt, next to the outdated flares. \$\endgroup\$
    – user16324
    Commented Sep 21, 2021 at 14:07
  • \$\begingroup\$ @winny. I am not discussing the safety issues here. They are taken care off. I try to gain understanding. \$\endgroup\$
    – Decapod
    Commented Sep 22, 2021 at 15:53
  • \$\begingroup\$ Well it is possible that the additional charge increased the internal pressure until the seal failed. \$\endgroup\$
    – user16324
    Commented Sep 25, 2021 at 13:57
  • \$\begingroup\$ @user_1818839. Not clear. Additional charge in reference to what. The cells were completly discharged and carefully charged under CC/CV conditions. Cell by cell. Why would the pressure go up under these conditons \$\endgroup\$
    – Decapod
    Commented Sep 26, 2021 at 15:04

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A properly designed Li-ion pouch cell, charged within the specified limits will not puff out. Puffing out is an indication of overcharging and/or poor cell design.

The pressure in a pouch Li-ion cell is due to the state of charge, not due to the act of charging. When the state of charge drops below 100 %, the pressure drops, and the pouch Li-ion cell recovers somewhat.

I say "somewhat" because a Li-ion pouch cell is permanently degraded if allowed to puff out, due to delamination of its layers. The proper way to build a pouch battery is to place the cells within a mechanical restraint with a bit of resilience to contain the pressure and prevent expansion.

And I say "Li-ion pouch cell" because "LiPo" is a widely used misnomer. The chemistry is "Li-ion", not "LiPo", and the format is "pouch", not "LiPo". A cell with a Lithium Polymer separator was developed, yes, but it never left the lab. Later, vendors co-opted the term when selling Li-ion pouch cells. Indeed, the chemistry in most pouch cells is the same as in the typical 18650 cell: LCO (Cobalt). And the technology inside it is the same as in a prismatic cell: a flat roll.

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    \$\begingroup\$ Wouldn't mentioning the dangers of charging mistreated Li ion packs be a good idea here? \$\endgroup\$ Commented Sep 21, 2021 at 13:29
  • \$\begingroup\$ OP is charging each cell individually with a CCCV charger. OP is being safe. \$\endgroup\$ Commented Sep 21, 2021 at 13:30
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    \$\begingroup\$ Avoiding just one of the potential hazards doesn't qualify as safe. \$\endgroup\$
    – user16324
    Commented Sep 21, 2021 at 14:07
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    \$\begingroup\$ Yes, given their affinity for fires, they should be disposed of properly at that point. \$\endgroup\$ Commented Sep 22, 2021 at 0:18
  • \$\begingroup\$ @user_1818839. Although the dangers are taken care of I would like to receive additional information on that subject. \$\endgroup\$
    – Decapod
    Commented Sep 22, 2021 at 15:57

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