First of all, it is certain that the battery has been put, and then charging may have safety problems. Cheap led lights may be lead-acid batteries, explosions are basically not, you can make a dead charge to see a similar lamp bought before, but also put, although you can also charge and continue to use, but obviously you can feel that the battery life is not good.
Decisively switch to lithium battery, sufficient battery life, usb charging is very convenient, that is, the taste is not necessarily caused by charging and discharging, it may be the taste of the material itself as long as the power supply is qualified, only about 4-5V DC voltage on the power line to charge (but the meter may measure the existence of a higher AC voltage, which belongs to reactive voltage, (Apple's usb power head has a high reactive voltage, according to an ElectroBoom video test)