Wife has a 4.5 year old Mazda CX9 on the first battery.
Wednesday night she left the dome light on for 20 hours. Next day it wouldn't start. Dome light was still bright though.
I put a charger on it. It showed 12.2v. I charged it for 3 hours at 15a, and 1 hour tapering down to 2a, and it showed 14.2v. As far as I can tell, it is a 55ah battery, so the charging seems right on.
The last two days it has been fine.
We got the car to haul kids back and forth to college, but that is over and we want to get something smaller; probably after we see the 2019s. (unless cars get a 25% duty and the prices skyrocket, in which case it is just fine).
So my question... should I be getting a new battery? I don't want to waste $100, but if I need one, I might as well get it while it is still functioning.