[Carty]

I've been using similar trackers to these for some time, they're very handy for cars you don't use every day. Frankly it even alerted me to the car I do use every day having a failing battery before I got stranded, so yes they are great. Wish the manufacturers would allow reporting on the battery condition via the apps this way, they have the capability in most modern cars.

Though I have to say I think the particular battery state tracker he's using is very dumb. It appears to be using the output voltage as a direct linear report of the battery capacity %. In reality this is a huge over simplification. The better ones will measure the capacity of the battery by measuring capacitance or resistance as well as straightforward voltage, and they'll give a better indication of charge % even when the battery is under heavy load and the voltage is sagging.

Anything is better than nothing I guess ?.