Wanted to share some early data on a little project I put together. It's a compact logger that records battery voltage and throttle input. My driver was to collect data on the voltage of the battery over the course of a run, as well as response to short term load.

I've no doubt there are commercial options out there, but I learn through experimenting and this is fun. The current prototype is a microcontroller-based unit with a microSD card slot. I had tinkered with using WiFi, but it just seemed like a pain in the butt, so I decided to just collect raw data and chuck it into a spreadsheet. Again, there are probably better data analysis tools out there, so you can run with what you like. What tool can't be happy with a CSV?

Without wires, it's just on 4g so not a burden, but a y-cable for the ESC is needed and it uses two alligator clips to attach to the car's battery.

Anyway, on to the fun bit! Did my first run just now and it's quite interesting:


Each sample is 20ms apart (I'm pretty sure I can go much higher) and there is a bit of noise, so the chart above uses a 20-sample moving average of voltage.

You can see a definite sag under load as the throttle is applied and a recovery as the car hits speed. In future, I hope to compare different batteries to see if this changes. There's also a bit of jumpiness in my throttle - maybe my radio is getting old.

You may also notice I started with a fairly depleted battery. Soz - I didn't have patience to charge it

Anyway, as I get a chance to get to the track, I'll try to collect more data.