There's a lot of mentions regarding essentially jumpstarting the dead battery cell (the 3 18650's soldered together) on the Theragun Elite, but I'm seeing a lot of conflicting info online where it's ''not'' recommended to do something like that due to the fact that if the batteries have discharged to a level where they cannot hold a charge, the chemical changes the battery undergoes makes it dangerous to revive. That is, fire/explosion risks.
Anybody more experienced with batteries/18650's that can shine a light on this? Debating if it's worth it to perform something like this or to get new batteries altogether.
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-- UPDATE --
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For anyone running into this post in the future, I can provide some data-points on my theragun elite.
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Had a brand new gun sitting unused for 3-4 years. Opened it up and it wouldn't take a charge. It would take 10+ hours from 0-100%, and once unplugged, drop back down to 0.
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Followed some helpful comments here and https://www.youtube.com/watch?v=_-uEJRH-GeI to get the gun opened, pulled out the battery and unwrapped it.
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You will need a multimeter. Multimeter measured voltages of each cell at 0.2-0.3V each. Didn't have any other special tools on me other than a wire stripping tool and an 18650 battery charger. Harvested a working 18650 battery from an old laptop battery (you should buy one if you can't find a spare), measured it at ~2.6v and thankfully it charged up fully with the battery charger.
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Stripped an old usb charging cable and pulled out the red and black wires for positive/negative charging. They were extremely thin but worked. Followed this video https://www.youtube.com/watch?v=orvdFk231SQ and used the wires to connect each cell of my battery pack to my fully charged cell, and got them each to ~2.5V. Plugged in the massage gun charger and this time around, started charging really quickly.
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Constantly made sure batteries did not get exceedingly hot. One of them were slightly warm at most. At ~50% charge, I unplugged the charger and let it sit for an hour/overnight. Both incurred a 0.02V drop which I was happy about. Charged it up to 100% and each cell measured at ~4.10V. Gun started up and works fine now.
There's a lot of mentions regarding essentially jumpstarting the dead battery cell (the 3 18650's soldered together) on the Theragun Elite, but I'm seeing a lot of conflicting info online where it's ''not'' recommended to do something like that due to the fact that if the batteries have discharged to a level where they cannot hold a charge, the chemical changes the battery undergoes makes it dangerous to revive. That is, fire/explosion risks.
Anybody more experienced with batteries/18650's that can shine a light on this? Debating if it's worth it to perform something like this or to get new batteries altogether.