We have been having problems with our car battery becoming discharged at irregular intervals of a few weeks, but so far we have had no luck tracking down the cause. So I decided build a monitoring device in the hope that this might give me some more information.
Several problems needed to be solved:
- A car is quite a hostile environment in the terms of temperature and moisture.
- Significant electrical noise and surges can occur in a cars system.
- I wanted to support firmware updates without having to remove the device from the car.
This is the circuit diagram for the project:
The battery monitor was been running continuously for 2 weeks now with no problems during some quite cold and wet weather. I have successfully done one over the air firmware update. So at least in the short term the problems seem to have been addressed!