I have a Wifi AP and its Li-ion battery has swollen so much that its cover cannot be put in place over it now.

Li-ion swollen batter

Its working but its backup time has reduced to 20%. I cannot put on the battery cover because of its bulge. Normally its mains charger is power-ON 24/7.

Is it safe to keep it working in this shape? Is their any recommendation as to when to replace a Li-ion battery? Is it possible that it blows up and catches fire?

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    \$\begingroup\$ I would not. Risk of explosion is still small but much higher than before it was swollen. \$\endgroup\$ – winny Jul 30 '19 at 8:07
  • \$\begingroup\$ What is the sign that tells the countdown to explosion has started. \$\endgroup\$ – alt-rose Jul 30 '19 at 11:24
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    \$\begingroup\$ The swelling. Still low chance though if the battery is recent and from any reputable manufacturer. \$\endgroup\$ – winny Jul 30 '19 at 13:08
  • \$\begingroup\$ This cell is on the way to failure. Remove and dispose safely right away. \$\endgroup\$ – Kripacharya Aug 2 '19 at 19:03

Provided it hasn't been over-charged, over-discharged or physically damaged it should be safe. But, why did it puff up? If it was overcharged, over-discharged or physically damaged then it could blow up.

Apart from that, puffing indicates that some of the electrolyte has turned into gas, which reduces the capacity and efficiency of the cell.

You should discharge this cell to zero volts, discard it and get a replacement.

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    \$\begingroup\$ Instead of discarding, recycling might be a good idea. Lithium isn't the most expensive thing but it's not cheap! \$\endgroup\$ – Hearth Jul 30 '19 at 14:18
  • \$\begingroup\$ Now when the battery is swollen is it OK to keep it unplugged from the mains and discharge it to a point that the device shuts-down due to low voltage? And then again put it on charger for charging. OR is it better not to discharge it to its lowest discharge point? \$\endgroup\$ – alt-rose Aug 6 '19 at 13:03
  • \$\begingroup\$ It is safe to discharge to the normal device shutdown point, but not below. Then you should remove it from the device and discharge with a resistor until it goes down to zero volts. Don't recharge it, do the sensible thing - replace it! \$\endgroup\$ – Bruce Abbott Aug 6 '19 at 21:39

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