Learning to check mobile phone charger voltage is also a big help when it comes to troubleshooting charging problem.
Various mobile phones have different varieties of charger packaging and designed but almost all of them have one the same operational concepts.
A picture below is an example of a charger used in Nokia Mobile Phones.
The concepts is that the positive voltage is in the inner side of the connector pin while the negative voltage is in outer side of the pin. Charger voltage range from 4.5 to 6 volts and an average rating of 800 milliAmpere current.
Checking it output voltage will be on its connector pin tips. Just set the analog or digital multi-meter to 10DCV or higher range. and connect both test probe to its corresponding polarities. A good and working charger will get the approximately correct reading while the busted one will get no reading.