AA and AAA battery tester

1 General

2 Project description



Simple rechargeable Ni-MH battery tester. The problem with those batteries is: right after you take them out of charger, voltage level at their terminals is good. But some old batteries will get empty/discharged way too quickly under normal load. This device is intended to discover old batteries with reduced capacity.

Freshly charged batteries are tested under high load for short time by shorting battery + and - terminals using 5 ohm power resistor (R1). Simultaneously battery voltage is being measured while under load.


I use vintage analog voltmeter. Instead of power resistor I use Nichrome resistance wire. Test/measurement button should not be pressed for long because power resistor gets hot quickly and battery is being quickly depleted during measurement.