I wouldn't rely on the seller to actually know what he is talking about. If you go to the Raveman website they tell you that you can hook their headlights to an external battery pack via the USB C cord if it goes into the reduced power mode when the battery is low. That's a pretty good indication that only charging it with a computer USB output is a bunch of hooey. The lights have overcharge protection so as long as the voltage (5V DC) is correct you should not worry. The reason batteries eventually fail is the number of times they are recharged. Most reputable battery makers list the output after 500 recharge cycles to be 80% of the original capacity.