how to repair 5v and 12v charger

Use a voltmeter to determine if the battery charger is producing electricity. Place the end of the red wire from the voltmeter onto the metal clamp on the end of the red cable from the battery charger. Place the end of the black wire from the voltmeter onto the metal clamp on the end of the black cable from the battery charger.

Read the voltmeter display. If it reads just over 12 volts, the charger is working (so the issue is your battery). If there's no reading, the charger needs repairing (so check the fuses). You may sometimes get a small reading of perhaps one or two volts. This is due to electrical resistance and doesn't mean your charger is producing electricity.