HOWTO: Open and fix a toy light-saber that refuses to charge - works when charging cable powered
This is a $20 toy light saber with a solid aluminum hilt. I show how to open it up and remove the battery, circuit board, LED module, and speaker. The interior contents are probably similar across a whole line of similar toys with different hilts. (I've also seen some with USB plugs built in, instead of the USB to barrel connector jack this one has.)
This particular lightsaber would not charge, but if the charging cable was plugged in and powered up, it would turn on and make light/sound effects. The problem was that the 1S BMS (Battery Management System) circuit board had failed. [I tried charging up the 18650 cell to see if it was just off due to a low power situation....but it would still not charge or turn on.]
1S circuit boards that attach directly to 18650 cells are quite inexpensive on EBay, so I bought (5) and replaced it, which fixed the light-saber.