johnkk

Noticed slightly slower cranking and occasionally the engine would hiccup at very light throttle. Ran a vcds scan and found intermittent knock sensor signal too high and intermittent voltage too low codes. Never seen those before.

Checked the battery terminals and the negative post was slightly crusty, so I dug out my terminal cleaning brush device and cleaned the posts and cables.

When I pulled the cables, I noticed a split/hole in the top of the battery near the negative post. The flat surface was deformed around the hole. Hmmmm. Almost looked melted. I guess that the electrolyte fluid level was getting low and perhaps a cell was starting to go bad or developed an intermittent short.

I replaced the battery and cranking back to normal. Codes have not returned. Bad battery was an Audi replacement about 4 years old.

Anybody ever see a battery develop a hole?

Airbag

im sure this one did !

SloopJohnB@mac.com

Yes. You're actually quite lucky because such holes often vent H2 and O2…not a good mixture to meet a spark such as might occur with removing a battery terminal to clean the post and terminal!

johnkk

Lighting a match to check electrolyte level.

Redd

Battery cases these days are usually molded and welded thermoplastics, so yes, they can certainly split on welds, or melt from internal heat from a number of conditions and defects.

These defects can often be caught early when there is a voltmeter in the car, but car makers don't want us to bother our heads with these highly technical matters, like counting to fourteen.

The odds are that you will never have another defective battery in your driving years though. That's good news.

SloopJohnB@mac.com

Priceless