I wanted to see if I could rejuvenate a battery that's dead and several years old but never saw much use. Sat in a car that mostly sits in the garage.
I stuck it in my '89 Toyota Cressida, cleaned the terminals on the battery and the cable ends, hooked them up and jumped it with the good battery. Car fired after a sluggish crank and ran but it idled high and the idle never really came down even after the car got warm. Normally when warm it idles around 600 RPM in gear. With this hinky battery it would idle in gear around 1000 and about 1500 in neutral. Also noticed the lights flicker from time to time.
After running around for about 15 mins, turned it off, no restart. Not even enough juice to get a grunt out of the starter. Okay, clearly the battery is beyond salvaging. Put the good battery back in, everything back to normal.
So - why was I seeing the symptoms I was seeing with that DOA battery in place?
Thanks