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I have three dead lithium-ion battery packs - two of these and one of these.

My multimeter informs me that the voltage of the batteries and they both read 5.6V. I understand that by dropping below the 3V per cell threshold, the protection circuit has kicked in and is stopping me from charging the packs. I have also read that it is possible to revive individual cells, by providing a 'boost' with a small current, when the voltage is below the threshold.

My question is this: is it at all possible to revive the whole pack (protection circuit included) without dismantling it?

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  • \$\begingroup\$ The current needs to be applied directly to the cell. \$\endgroup\$ – Ignacio Vazquez-Abrams Aug 24 '17 at 18:47
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I only have experience with batteries from one supplier, but in that case, when the voltage went too low the circuit was effectively disconnected. If you are seeing 5.6V then the protection circuit hasn't actually cut off access to the cells.

It is possible that the protection circuit isn't preventing charging, but that your charger isn't attempting it.

I would try another charger. If it doesn't work, I'd try to inject a small current into the entire battery pack until the voltage gets high enough for your charger to be happy.

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  • \$\begingroup\$ Thanks for the response. I have other chargers but they don't seem to be working either. However, I do have a bench top power supply and am in the process of buying a resistor to get the current down to a few mA. \$\endgroup\$ – Beginner116412 Aug 29 '17 at 8:27
  • \$\begingroup\$ @Beginner116412, does your bench supply have a constant-current mode? If so you won't need the resistor :) Please let us know how the experiment turns out! \$\endgroup\$ – bitsmack Aug 31 '17 at 5:50
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Maybe - with individual cells I have revived them from under-voltage shutdown by injecting a small current through a moderately high value resistor from a power supply higher than the cell voltage.

I have never attempted with a multi-cell battery.

It will depend upon the protection circuit. I used a few kilohm resistor fed from 8 or 9 volts to inject 1 mA or so until the protection circuit re-enabled.

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