Leaderboard

It is, indeed. And the reason I reply to a fairly old thread, is a similar experience, but with a little addition - a little hint (but a long story, apologies). It might work in some cases. Li-ion batteries are delicate on one hand, but on the other hand, due to the built in electronics, they can survive better, than the NiMH batteries for example. (I understand in some places of the world it is advised to use disclaimers - without repeating his words here, please refer to the OP's disclaimer at the top of this thread.) Few days ago I bought a small bunch of junk minidisc walkmans (for peanuts really), just out of curiosity, to see how they look like inside. I can tear them down without any fear, and I maybe able to learn new things. One of these was a Sony MD-R30, little beaten, but it turned out being fully operational, and just run nicely plugged on my MZ-R3's power adapter (even it was only 5V, while the R30 would have needed 6V, according to the sign next to the inlet). Then I noticed, that there is a battery in the unit. It looked completely dead, no voltage on the terminals, and it did not take any charge either. I decided to check it inside - I did not have any replacement battery, but I had an experience, that suggested I should try it again. Few years ago, I once accidentally left a battery of my tiny Sony camera (DSC-T7) in the watch pocket (coin pocket) of my jeans. My wife did not notice it, and put them into the washing machine. It took me some time to realize where I left the battery, but by then the washing program was almost complete. Needless to say, the battery was completely drawn, worse than that, even the external charger indicated it was faulty. I had nothing to loose, opened the miniature case, and disconnected the internal controller board from the battery. It showed only a few hundred mV, but it was a sign, that it is not yet completely dead. Then I connected the battery to a CC PSU (constant current power supply). At about 5 Volts, I began charging the battery with ~100mA current (* more about the value below), and monitored the voltage. It soon jumped up to ~3V, then I gave a couple of 5-10s impulses of 200...300mA, with equal length of "breaks" with 100mA in between. After this treatment I reassembled the battery, glued the case, and I have been using that battery since then, just like a normal one. Based on this story, I gave a chance to this LIP-12 pack too. I assumed the unit has not been in use for many years, and it depleted the battery. An alkali or a NiMH battery would have certainly died, but the Li-ion is protected from completely discharged, by the internal controller board. When I desoldered the 18650 cell from the controller board, it showed (what a coincidence) a similar 8...900mV. Then I performed the procedure above. I chose 200mA charging current, and 500mA for the impulses. The 200mA is about the 1/6th of the nominal capacity of the pack in mAh - the rule of thumb is 1/10, but while that is appropriate for regular charging a healthy battery, here I wanted to get some quick results. After a few minutes the voltage went up to 3V, then I repeated the impulses, finally, left the battery on ~150 mA for about ten minutes. At this time, it showed ~3,7V - that is good, as the nominal voltage of the pack is 3,6V. I resoldered the cell on the board, reassembled the pack, a few little drops of superglue on the edges of the case, and it looks as before. When I slipped the pack back into the compartment, the unit immediately showed ~50% remaining charge (that instant value was a bit "fake", but definitely a good sign), and after plugging the wall adapter in, it began charging. Playback did not stop when I unplugged the power adapter, so the battery was back in life. I will experience a bit around the real capacity of the "revitalized" cell, but so far so good. . . . .