My Bluetooth speaker, which had an integrated 3.7v battery, died and ceased working.
The speaker does not work on its own when plugged in, presumably because the battery is dead.
I went out and got a 4.2v battery to replace it. The initial battery charge worked and kept the speaker working for a while until the charge was gone, at which point I attempted to charge the speaker via the USB port designated for charging, but it failed.
The store where I bought the battery claimed that switching between voltages was not a problem, but it appears that it is. Is there any way to solve this?
I've read some tutorials, but I still have no idea.