Arduino Battery AA 1.2V Capacity Tester

thingiverse

First off thanks to deba168 for the fantastic battery capacity tester! https://www.instructables.com/id/DIY-Arduino-Battery-Capacity-Tester-V10-/ For reference: In the left diagram of deba 168 is missing the connection of the right 10k resistors to the ground. On my screen, the order of the contacts was different. I've always been curious about what capacity the partially old AA (AAA) batteries still have. Deb's tester only needed to be modified from 3.7V Li Ion batteries to 1.2V NiMH batteries. I replaced a 10 ohm resistor with a 2.2 ohm 10 watt resistor, which resulted in a discharge current of around 400 to 600 milliamps flowing through the circuit. In the ino file, I adjusted the values for the 1.2V battery and changed the error message output to two lines. The displayed voltage and current readings are remarkably accurate. With my multimeter, I measured a deviation of 12 millivolts from the actual voltage reading and 10 milliamps from the actual current reading. The accuracy depends on the tolerances of the 10k resistors used in the voltage divider and the load resistance. I highly recommend measuring the load resistance when it's at its warmest (about 50 degrees Celsius) using the shortest test leads possible, then entering that value into the ino file. The enclosure has snap closures but can also be screwed shut. My PCB measures 97 x 52 mm in size. The files include the ino file and the library for the screen display.