A 12V Battery Monitor for an Electric Car

[rgsparber]

I own a Chevy Bolt EV. The designers did a masterful job monitoring the 400-volt traction battery, but ignored the 12-volt battery, which powers the car's computers.

When my 12-volt AGM battery recently became weak, I saw random failures in the computers. A load test of this battery showed it was bad What I needed was an early warning that the battery was about to upset the computers.

I have built a computer-based voltage monitor that continuously measures the 12-volt battery at its terminals. When it detects a voltage below 12.00 volts, it takes five more readings and then votes. If the voltage dip persists, it locks into an alarm state. An LED flashes and a beeper sounds. The alarm tells me to run a load test.

Before you get excited about using a computer for such a simple task, understand that my computer is an ATTiny 85, which costs $3.33. The total cost of all parts is around $10.

If you are interested, see https://github.com/rgsparber/Chevy-B...attery-Monitor (my website is temporarily down).

My website is back up so you can get the document here.

Rick