Recharged battery and wiring smoked!
 

My 300CE has been mostly sitting. I've been chasing a circuit that drains the battery. It started fine last week after charging the battery. I took out some of the fuses that had voltage with the key off and the battery seemed to hold a charge for a few days until a couple of days ago. I charged it overnight and when I tried to connect the cables, it would arc as if the cables were backwards. I had the key on so I removed it. It didn't arc when connecting the battery cable but then the car began to smoke soon afterwards. It may have shorted and began heating the wiring before I turned the key. White smoke billowed and I shot it with an extinguisher before removing the cable. Obviously a short apparently at the battery wiring that runs right in front of it to a junction at the bottom near the hold down bracket.

Note: the PO rewired this for a momentary starter button under the dash that works when the key is on. Some time ago I couldn't find where he tapped into the ignition wiring so I left it that way. Now that I need to repair and check the wiring, I will try again to return the ignition wiring to original.

Questions:

1. The battery measures 11.9V. How do I know it's ok?
2. Could I have overcharged the battery?
3. Any pointers finding the cause of the wiring overheating and melting the insulation?

Did you by any chance charge the battery backwards? Check voltage and polarity, the red ground and black positive cable can make things tricky.

You're right, I charged it backwards!
 

Polarity is reversed. :eek: Can I drain the battery and recharge or is it toast?

What kind of damage does this do? :confused:

Felix

looks like it's correctible:
source

now to figure out how to drain it...

pifcat2, switch the battery connectors then turn on the headlights and radio and fully discharge the battery. Remove/reconnect the battery connectors in the proper configuration and recharge the battery correctly.