Bad battery or parasitic draw?

[The Dude]

I had my battery charged because it was dead, now is pulling 12+ volts. I hooked the positive and negative cables up and immediately checked the volts with a multimeter and almost instantly they're at around 8V and dropping rapidly. After removing the cables off the battery it starts returning to the higher volts. Only thing I've done electrically recently was pull the radio out to get to where an oil pressure gauge was wired. There was a very thin ground coming out that I had to remove and screw down again but I even tried unplugging the radio altogether and that didn't change anything.

So would a bad battery act that way or do I need to go on a parasite hunt now?

 

[Kckazdude]

If your volts drop from 12V to 8V just by hooking up the negative cable it isnt a parasitic draw. Thats like a bulb lit up somewhere lighting up a dark tunnel.

 

[jetjock]

Ask yourself what battery voltage typically falls to while cranking. That should shed some light on the subject...

 

[The Dude]

Ask yourself what battery voltage typically falls to while cranking. That should shed some light on the subject...

Alright, so if I'm not cranking and getting this behavior from the battery something must be stuck "on" when it shouldn't be, correct? Would the ignition switch cause that or the starter(~50 miles on it)? Or am I missing the hint completely?

 

[jetjock]

You're missing the point. Cranking loads are in the neighborhood of 150-200 amperes. Because of a healthy battery's ampacity even under those conditions voltage doesn't fall below 10-11 volts. Put another way if you had parasitic current flow of such magnitude to drop a good battery to 8 volts through other than the starter wiring you'd know it. That situation would involve new fuses, a fire extinguisher, or a bag of marshmallows...