This is very vague, I know, but if you have questions that could perhaps lead this question to an answer, please ask!
I built a car starter that takes commands over SMS. So I can text my car to do stuff. Neat.
Originally it failed because one of my relays decided to stick on one night, and my radio was on, draining the battery.
A quick google search pointed me towards the fact that I didnt have any reverse biased diodes for inductive load protection!
Alright cool. So I threw some on there and did an endurance test of my circuit to make sure nothing would fail again. I did this over night (relays were switching on an off, but were not actually switching on any load). Video here FYI: http://www.youtube.com/watch?v=cLCTgyNxEdE
So I happily put my car starter back in my car. And it worked!!
For about 2 days. I woke up this morning to a dead car again.
Q: Does anyone have any idea why this could be killing my car??? The circuit, when asleep, draws 60mA. I believe thats not enough to kill a car battery in a couple of days.