They are all used lithium batteries, lithium batteries have no memory effect, do not need to be charged after running out of power, and it is easy to damage lithium batteries. So it should be able to charge at any time, you can also stop charging at any time, but you can not run out of battery power. airpods must be fully charged for more than 8 hours on the first charge, and repeated several times to fully charge and discharge, a process called activation, which allows the phone's battery to reach its maximum capacity. The phone must be unplugged as soon as it is fully charged, as overcharging can damage the battery.