Ampere Tests Android Phone Chargers
Android: A defective charger can seriously harm your smartphone. If your phone is compatible, the free Ampere app checks the power of your charger.
Ampere tells you how well your battery is charging and if there are any problems. It does not work on all phones, but you can view the list of incompatible phones on its Google Play page – I tested it on a Nexus 5. One old charger was found that was not fully charged and all the others were tested ok.
Ampere (Free in-app purchase removes ads) | Google Play via WonderHowTo