reparing/restoring li-ion battery ?

[Frank Bemelman]

I have a Sony MD-player MR-Z30, has been sitting on the
shelf for perhaps 3 years. The LI-12 battery was dead,
and it didn't recharge when the player is plugged in with
the AC-adapter.

I took out the battery, and hooked it up to my bench
power supply. When set at 3.6V there was no charging
current. Increasing the voltage, it started to charge
a little bit, some 25mA at 7V perhaps. I set it at
8.5V, and dumped about 100 mA into it. Disconnecting the
power supply, the battery voltage dropped to 2.2V again
immediately.

I left it on my powersupply during the night, and this
morning, the battery (when disconnected) gives 3.6V
and the player actually runs on it, but indicates an
almost flat battery.

I hooked it up to the bench supply again. At 4.2V it
hardly charges the battery, 1 mA?, meter doesn't
show anything. At 6V it charges 10mA, and at 8V it
charges 80mA. Some improvement maybe, not sure.

Are there any guidelines to revive bad li-ion batteries
or is it considered a hopeless situation?

--
Thanks,
Frank Bemelman
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