I have a portable Bluetooth speaker with a very short play-time on a single charge and I want to know if I can swap the battery for a larger one.
I've disassembled it enough to see that it's driven by a single board that has all the controls, speaker drivers and battery connected to it. The speaker turns on a red L.E.D. when it is charging, but that light does not change/blink/turns off unless you disconnect the charger, so no practical way of knowing how long it actually takes to charge the battery. When the battery discharges, a badly pronounced English message is played through speakers and then the device turns off.
The battery is covered by a shrink wrap so I haven't read its rating yet, however, it is very small, rectangle shaped. Aprox 2 x 3 x 0.4 cm (1 x 0.75 x 0.2 in). It is connected to the board via two cables
I may be able to source a 18650 cell from other devices that failed because of something different than battery, so battery cost is not an issue in this case.
I've seen readily available chip boards for charging Li-ion batteries that only state battery voltage as compatibility parameter. (3.7 v nominal, most cells available are also this voltage). That makes me think that those chips have the logic to charge any battery size as long as it is a 3.7v cell
If that's the case, what should I check in the speaker or in the possible replacement battery to determine whether they are compatible? By compatible I mean the board will be able to charge the new battery and shut itself off before over discharge occurs. The board's power input is a regular USB mini port. (5 volt)