Battery exploded!

[03silverA4]

A few months ago my battery literally exploded in the car. Never seen anything like this, the battery plastic was torn open and I had acid all over the battery compartment and windshield. Almost needed a change of underwear after that experience.

This could have been caused by a wire which got loose at the light switch. Probably my fault and my janky boost gauge wiring but oh well live and learn.

I have been procrastinating on getting the car working, but tired of looking at an expensive yard ornament...lol

The car still starts but acts really weird. When started from cold it will idle at like 900rpm which is really low for cold start, the a/c controls and radio keep turning on and off and the battery light, brake light are on.

Where do I even start diagnosing this? Should I get the VCDS software? https://www.ross-tech.com/vag-com/VCDS.php to start with? How do I find out what is fried and what needs to be replaced? Should I go ahead and replace the voltage regulator anyways since its fairly cheap part?

Please help!

[kwilson]

You started with a new battery, right?

[03silverA4]

You started with a new battery, right?

Yes lol

O'reilly took care of the battery under warranty, should have seen the face of the guys when I brought battery blown up lol

[Mike Tries]

Batteries naturally produce hydrogen gas. Cars that have their batteries enclosed in the trunk will usually have a hose to vent this. Cars like ours have no such provisions since they are open to atmosphere. If there is hyrdogen gas venting near the battery, and something causes a spark, kaboom. This usually happens when you are far from help and you forgot your cell phone and you need to walk a mile to a pay phone and call your friend's dad, who is out at the pool, but thankfully brought the cordless phone out with him.

[Kevin C]

Stock our cars have a battery vent that is routed outside of the plenum (uses a tube hooked up to the battery). However, this one sounds like the explosion was internal to the battery. Most batteries have a flame arrestor. This sounds like yours did not have the factory style vent and a battery that did not have a flame arrestor on its vents. The other possibility is it had an internal failure that caused it to ignite.

[EuroxS4]

This type of thing happens with shit quality batteries or a drastic and fast temperature change.

[03silverA4]

Does anyone know what to start checking first to get the car back on the road?

[Mike Tries]

Look for damage that may have been caused by the acid from the battery. Or, I suppose, the explosion. Local damage.

[Erikbecker]

Does anyone know what to start checking first to get the car back on the road?

I think you may start with a thorough inspection of the wiring, especially around the light switch and boost gauge areas. The VCDS software is handy for figuring out what's going on in the car's system.
Considering the odd behavior you're experiencing with low idle, intermittent A/C and radio, and warning lights, it could be related to electrical components affected by the battery explosion. I'd suggest checking for any visible damage to wires, connectors, or fuses. The VCDS can read fault codes, which might give you more clues about the specific systems affected.
As for the voltage regulator, replacing it could be a smart move, given it won't break the bank and could sort out charging system issues.

[03silverA4]

I think you may start with a thorough inspection of the wiring, especially around the light switch and boost gauge areas. The VCDS software is handy for figuring out what's going on in the car's system.
Considering the odd behavior you're experiencing with low idle, intermittent A/C and radio, and warning lights, it could be related to electrical components affected by the battery explosion. I'd suggest checking for any visible damage to wires, connectors, or fuses. The VCDS can read fault codes, which might give you more clues about the specific systems affected.
As for the voltage regulator, replacing it could be a smart move, given it won't break the bank and could sort out charging system issues.

Ordered voltage regulator, we shall see what happens.

[03silverA4]

She's back on the road!

Found wire by the light switch which got loose and touched bare metal that's what fried stuff. Fixed that.

Replaced voltage regulator - that fixed battery light flashing and low and high voltage codes.

Replaced coolant temp sensor behind head - that fixed coolant temp code and misfire

Replaced low beam bulbs - both were blown

So far drove about 10 miles with no lights and hit boost several times.

So glad ECU is not fried the Maestro software is registered to this ECU...

[Mike Tries]

Nice!!! Congrats!

[03silverA4]

Nice!!! Congrats!

Now I'm kicking myself for procrastinating on doing anything with the car for 4 months, since the fix was less than $200 and I put maybe 4 hours total in research and labor to fix it.

[Turbo510]

So it comes down to the voltage regulator; that caused burned out bulbs, etc., and also over-charging of the battery which produced the hydrogen gas. Modern "maintenance free" batteries don't create much hydrogen, unless abused like your battery was.

I've seen one battery explosion; in a gas station. The Cadillac driver went to start it, there was a bang under the hood, and a puddle of electrolyte spread on the concrete under the engine compartment.

[walky_talky20]

Indeed. Battery light flashing was the first clue. Immediately having the battery and charging system tested probably could have avoided the explosion from overcharging. This would include a voltage and amperage monitoring with variable loads applied to check the performance of both the battery and the charging system. This would identify the failure of the voltage regulator very quickly and easily. The quintessential tool for this back in the day would be a Sun "VAT-40", Bear "ARBST", or similar. Lots of different tools out there today - Snap-On EECS, Autometer BVA, even Harbor Freight stuff.