I had M and S come on and went into Limp Mode on Friday afternoon. I got home and put the car in the garage for the night. Saturday I came out to check the battery and other cables. Took battery out and found that the hold down clamp bolt had melted into the back side of the battery. When I removed the battery there was a small drip of battery acid coming out. I need to replace the battery, but need to find out whats causing the hold down clamp bolt to heat up. Any ideas? Also appears to be a disconnected sensor that was sitting in the battery tray. Any help appreciated! Thanks



Battery nearly melted through. I small drip came out when I removed it.

Hold down rod was heating up

This was not connected and was sitting under battery.

 

You're lucky you didn't burn down your garage/house. If that battery would have melted a bit more...and caught fire...game over. We had a battery fire last month at work, vehicle was minutes away from becoming toast.

You'd assume the battery hold down came in contact with the positive post, to cause that type of melting/heat. But, you don't mention that happening. So, it could be a defective battery, with two plates touching together inside, or something? Or you lost your main ground, and it tried to ground itself through the surface voltage of the battery? If a battery is super dirty, you will have a larger amount of surface voltage lose but, this would be very uncommon. Was the hold down maybe over tighten and cracked the battery housing, still wouldn't explain heat build up though?

Just a good thing you checked it out. I'd be very thorough about reinstalling battery, looking for any rubbed through cables or bad connections.

That sensor is suppose to be bolted to the radiator mount.

​​​​​​​ Brian.

 

Thanks I think the clamp down bolt actually rubbed through the battery casing. The clamp was not 100% fitted onto the battery and it was pulling that bolt forward into the battery. I checked all cables and they are ok.
The negative cable is mounted to the clamp down bolt before it connects to the post. Not sure if that's right?