I was given a perfectly working aiwa Minidisk portable player (AM-F70). But the battery was dead. The multimeter read 0.00V after 2 hours of charging. I seems there is absolutely no source for the obscure battery in this deck, so I tried a trick that I never had the opportunity to test: Took a 12V power supply and touched the poles of the dead battery with that to trickle charge it. The actual Li-ion battery for the aiwa is rated at 3.6v. After the first 10-20 second revival charge, the meter read 0.5v or something. After a few more cycles, it read 2.5v. At that point i mounted the battery back to the player for a proper charging with the unit's charger. After about an hour or more it stopped charging and I tried the unit off the battery. It works. It played a complete MD of 74min and still was 3/3 charge. The specs for the unit are for 10 hours continuous play, and this is something I will test today, as soon as I find a MD with decent music in it.