DIY 3.6V 1/2 AA Battery Tester

In this document, I show a very simple tester to build, consisting of 5 components, for 3.6 V 1/2 AA batteries used by some electronic devices; for example, these are used industrially in Schneider power switches, as well as in motorcycle anti-theft clamps or some camera models.

Photo 2: Schematic, list of components. 2 pieces of sheet metal for contacts with the battery, 1 1N4002 diode or any from the 1N400X series, a 33 ohm 1/4 or 1/2W diode bias resistance, 1 1K5ohm battery discharge resistance, and 1 blue LED since they operate at 3 V.

Overview of 1/2 AA battery features.

For example, used in: Motorcycle anti-theft clip batteries.

Detail of the voltage-reducing diode used, model 1N4002. I am not showing the step-by-step soldering process, as performing the 6 solder joints with an electronics soldering iron is a very basic task.

Views of the already assembled tester; I have used 100% recycled material from other electronic devices.

The diode is fully protected; if we reverse-bias the circuit (backwards, clearly the LED will not turn on).

3.6 V battery tested with the multimeter in battery tester mode, it measures 3.35 V, so the blue LED on our tester lights up without issues.

Checking a worn-out battery, less than 2.82V has almost lost one volt from the nominal 3.6 V, so it is already severely discharged, the blue LED does not turn on or does so very dimly, BATTERY DISCARDED.

To cover the assembly, I used red heat shrink tubing.