I mentioned before I was going to make a 12 volt lead acid battery tester at one point. I’ve repurposed the single AA tester I had made back in 2017 and converted it to test higher voltage batteries. Without repeating myself from earlier posts I have just decided to keep this short and just put the 12V tester version on the original project page rather than creating a new one. It works just the same as the AA version in that it displays total runtime and approximate Ah capacity. It is a cut down version of my 24V lithium battery tester which I made for work. The original project page is here. You will want to scroll down to the latest updates section where you will find the schematic and code.