Just in case anyone is interested,
i tried building a capacity tester with an arduino a couple of years ago, with inspiration from another instructable. But i didn’t get it to work properly, so i bought an opus bt-c3100 instead when they became available :bigsmile:
I made an analyzer (PROTOTYPE) that writes the voltage/amp values to a SD Ram card, which makes it easy to quick graph and look at the results. Most of the wires from the arduino (right side of pic) are for the SDRam, a switch to start things, and a display which shows progress. On the left is the resistor pack (salvaged from an EFI injector conversion), and a relay, with wires that go to the arduino to read the voltage every second. The arduino controls the relay, which cuts the drain circuit on low 18650 voltage or any other weird readings.
