At 22 years old (as of 2026) my Rio Carbon MP3 player was fully dead. Plugging it in to a USB charger or computer elicited no response, nor did any combination of holding or pressing buttons. Not too surprising given it's age.
Some gentle prying got the back cover off without damaging too many of the internal plastic clips, try not to open and close your Carbon too many times if at all possible, and revealed an APlus/Callisto 061947-DN2, lithium ion battery with the date code 32nd week of 2004. When checked with a multi-meter I found that the voltage being delivered to the mainboard was exactly 0.0v. That seemed low even for a >20 year old cell, which lead me to believe that the battery protection circuit had kicked in, disconnecting the cell from the device.
Some fraction of battery protection circuits can be coaxed into re-connecting an otherwise dead cell by applying a voltage to the output terminals. I used my 121GW meter, set to diode test mode, as it will put up to 15v for testing white LEDs and zener diodes. After about 30 seconds the meter crept up from 0.0v to 3.5v, I quickly plugged the device into a charger and it woke up! The screen lit up, the HDD spun up and the first track in the first directory was displayed. Good news, all the functions seemed to work as expected, but the battery life now was best measured in 10s of seconds.
I made some measurements of the original battery and found there was space for a new battery up to 48x19.5x6mm, not a huge space but there are lots of modern devices that use smaller batteries to do much more. It took some time but I eventually found a listing for 420mAh "602040" (40x20x6mm) lithium ion cells on Aliexpress. They are a half of a millimeter oversized but pouch style batteries are a little squishy and the original cell had padding.
Three weeks later the new cell arrived and it looked like it was going to fit. I de-soldered the original cell and removed temperature sensor taped to the end of the cell. Then I clipped the leads of the new cell to length and soldered it in. The fit was not fantastic but after transferring the original copper foil, foam padding and thermal sensor kapton tape, things were pretty snug.
Before closing things up I plugged it in and verified that not only does the new battery charge it holds a charge significantly better than it's 22 year old cousin.
After only 10min of work (and 3 weeks of shipping), my Rio Carbon was back in working condition!
