So I was resetting the ecu today and I noticed when I put the - terminal back on there was a spark. So I grabbed my trusty multimeter and checked the current between the car body and the - terminal. Turns out the car had taken a +12.7volt charge.
WTF.
How is the + leaking into the car and building up. I found that if I have the - off the + charge build slowly from zero in a few seconds. Does this mean I have a stray wire somewhere thats slowly just wasting power when the battery is hooked up properly?

Does this happen to anyone else? It might be a current leak through the alternator or something. Perhaps one of my amps has a small short.

 

In this case it is amperage you want to measure. Disconnect the neg cable again and put the meter pos to the battery post and the meter neg to the cable. (Meter in series with the negative).

< 10 milliamp is the normal draw for the ECU and clock/radio.

Do you have an under hood light? Did you have a door open? Sometimes i get a spark - not a worry unless the battery seems 'sluggish'...