The project is simple and was whipped up in an hour or so from spare parts I had. I'm going to mark it as done but some day I'd like to make a PC side companion app, nice pcb, etc etc. I don't test enough batteries to justify it just yet.
The hardware is an arduino mini, an ADC (MCP3208 soldered onto a breakout) 3.3v reference (REF3033 soldered onto the same board) and then an ATTOPILOT 180A current/voltage shunt sensor. I had an extra.
The test rig was this device, to measure cell parameters, and send it over serial to the computer to be recorded once per second. The load would dump into mag wire (12 or so feet) coiled in a 5 gallon container of water to act as an energy sink.
All metering was calibrated on two seperate high end power supplies and fluke meters, so I know its reasonably accurate. What I don't know is right or not is my own calculations, are correct.
Also, I admit I ran the battery into the ground a little at the end. I wasn't paying close enough attention. I will make some nicer directions and whatnot if anyone wants or actually needs help making this thing.