How to revive old lithium cells?

[dnix71]

I get lithium packs from metal scrappers that need work. Usually the balancing board got wet or a cell or two shorted out. Replacing dead cells is easy enough, bad boards mean stripping the pack for cells. Recently I got two packs that were simply weak. All the cells worked but did not put out enough current for more than a few seconds to power the device.

So I have a bunch of 18650 4v cells that are only suitable for a flashlight or portable radio. Is there any way to revive these cells? I got 2 nicad packs from an older Harbor Freight impact drill that came back by a slow long complete discharge, but a complete discharge on a lithium cell is supposed to be bad for the cell.

[Bruce S]

I have tried reviving no less that 20 of the 18650s,,, no luck on any of them. I don't think the chemistry allows them to be revived.
From all my training and reading, once they go dead, they can actually go reverse polarity (I currently have 2 that show reversed voltage ,so they are both sitting in a tin bucket of play sand).
If you find a way that is repeatable, let me know too.

Best of luck
Bruce

[XeonPony]

I get lithium packs from metal scrappers that need work. Usually the balancing board got wet or a cell or two shorted out. Replacing dead cells is easy enough, bad boards mean stripping the pack for cells. Recently I got two packs that were simply weak. All the cells worked but did not put out enough current for more than a few seconds to power the device.

So I have a bunch of 18650 4v cells that are only suitable for a flashlight or portable radio. Is there any way to revive these cells? I got 2 nicad packs from an older Harbor Freight impact drill that came back by a slow long complete discharge, but a complete discharge on a lithium cell is supposed to be bad for the cell.

Basically it is fatal to a cell, if voltage goes to 0 or near 0 it is done for, you can never trust it again

[Jackir]

I've had some luck reviving weak lithium cells by doing a few charge-discharge cycles. Try charging them fully and then discharging them slowly (not all the way to 0%) a few times. It might help improve their capacity.