Removing a battery from a mobile phone while it is running can leave the phone unable to function properly once the battery is replaced, warns a German product testing agency. In such cases, the reassembled phone might not recognise that the battery is charged, says Stephan Scheuer of Tuev Rheinland.
If the problem shows up, one solution is to let the phone charge for a very long time.
"Really long. Let it charge for 10 to 12 hours," he says. If that doesn't work, consider taking the phone to a specialist and asking to test out a replacement battery. If the phone functions, it should then be properly powered down to prepare for its original battery to be remounted.
"Then you put your battery back in," says Scheuer. If it again doesn't work upon restarting, then it's time to buy a new battery.