based on some preliminary research, the lot should take about 20mA max when idle... this is frankly, sod all, so there's no reason it cant be powered off the constantly live feed from the car, circuit redesign needed, but means I can get rid of the LiPo and charger, and add another buck converter (one for sense wire, one for constant power)

In other news, testing the battery power, just for personal interest really, this is modified main loop of the code showing the test code, every hour it adds a line to a text file to say its still alive, estimated lifetime should be a number of days, actually ill change it to every 20 mins, so I get better resolution...