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How close was I to dying?

I’m not sure if this belongs in the Repair and Maintenance section, but here goes.

A few years ago I was attending an auction that included some antique cars. While I was in that section, I kept smelling a rotten egg smell, and I was trying to figure out where it was coming from, so I went over to a car that had the hood up. I heard somewhat of a quiet rumbling/boiling sound, but I couldn’t figure out what was causing the smell.

A little bit later, someone noticed a little bit of smoke coming from the engine area and hurried up and unplugged the old fashioned battery charger. Apparently what I heard boiling was the battery!

I have occasionally wondered after that day how close I came to having something catastrophic happen when I was near the car.

Not very, unless you lit a cigarette or caused a spark while you were near the battery. The fumes wouldn’t have hurt you (as long as you weren’t right on top of the battery) but a hydrogen explosion/acid bath sure could!

No, I wasn’t doing any of that, but I was wondering if it would have exploded on its own from being overcharged.

And in the interest of safety I would have started Texases reply off with
"You could have been seriously injured had the battery exploded."

Whenever you hear the sound of something boiling, it’s alway prudent to back away until you find out what’s cookin’. If the coolant had been boiling and the radiator cap had blown off, you could have been scalded by that also.

I didn’t stick around after I heard that…

The rotten egg smell was the gas hydrogen sulfide, one of the products of overcharging a storage battery.

If the hood was up there could not have been an explosion. An overcharging battery gives off hydrogen gas. If a pocket of hydrogen builds up under the hood, it could indeed produce a (very) small explosion. It might even dimple the hood but do little else. And if the hood is raised, the hydrogen quickly wafts away. Nothing to explode. No danger except the exposure to hydrogen sulfide fumes. Sorry.

Thanks Steve, that’s what I was trying to find out.

My thread title is a bit of an exaggeration, if anyone was wondering…

I was on a trip to California and learned the smell of rotten eggs means a fried battery, I do not recall how long it went on, I imagine a battery could potentially explode or blow the covers off, it probably would not be life threatening but vision and skin certainly could be affected if you were in the right place at the wrong time.

Unplugging the charger from the wall was the correct move…Grabbing one of the clamps connecting the charger to the battery and removing it could / would have created a spark which could easily lead to a battery explosion…There is enough gas trapped inside the battery to rupture the case and send the hot acid flying…

For a battery to explode without an outside spark is very, very rare but it is possible should an internal cell connector fail creating a spark inside the battery…

A fully charged car battery has a lot of energy in storage…Should an internal short develop, under certain conditions, the rapid discharge of the battery, the release of all the stored energy, can boil the electrolyte, melt the case and make a BIG mess…

A wet cell car battery can explode, bursting the case and throwing acid and pieces of the case several feet in all directions. It has happened to me and the experience will bring to mind all the warning that are posted on chargers and test equipment. Luckily I was doing things by the book when the explosion happened because prior to that I wasn’t always so careful. Overfilling a battery blocks the vents and can worsen the chance of the case bursting first and subsequently causing an explosion when a short circuit occurs.

Fortunately that probably won’t happen with my battery charger.
If the battery isn’t taking the charge, the charge is aborted.
When the charger senses the battery is at full capacity, it switches to maintain mode.

I am hesitant about using “old school” chargers for the very reason OP mentioned.
I have seen plenty of my colleagues connect their old school chargers, walk away and do something else. Later, when the smell reminds them that they should have been paying attention, the battery is cooked. Literally.

Yes, it was a “vintage” charger, the type that sits on the floor with wheels.

They do have their uses, but it can be unwise to leave them unattended.

A battery can explode with the hood up and battery outgassing involved. This happened in a well ventilated Subaru shop when a poor charger connector popped loose about half an hour into charging and set the gas off.
This happened at lunch time and was noticed due to a loud 4th of July boom and the windows at the service desk rattling.

The car had been towed in right before lunch for a no-start complaint and the battery was ripped wide open. Luckily, it was at noon and there was no one around it when it went off.

This shop also had an emergency, high water volume shower stall in the shop for situations in which someone got doused with battery acid, set on fire, etc.

@Ok4450 And Other Car Folks, Yikes !
Hearing Of That Incident Is A Reminder Of The Importance Of Protective Eye Covering Whenever Working With Or Around A Battery, Especially When It’s Charging, In The Car Or Out Of The Car.

Not only can acid be thrown in your face, but shards of plastic and lead going 100+mph, too.

The only almost battery disaster I’ve had was when I was carrying a battery that had a cracked case and acid spilled all over my legs that were covered by car dealership uniform “rental pants.” I headed immediatel for the shower and wasn’t injured. I found out 100% poly-whatever pants aren’t injured by the acid, either. They must be made from recycled battery cases.
CSA

Chargers with a BOOST TO START function are the most likely to cause a problem. On the BOOST setting voltage is raised to 15v +/- and amps can exceed 100. If a battery has an internal failure and is put on a fast charger one cell might begin boiling and gassing and when the starter is engaged the load will pull the current up and something will give somewhere.

Let me repeat, overfilling a wet cell battery significantly increases the danger, and any spark near a gassing battery can cause an explosion. Most DIYers don’t have the large BOOST chargers and the most current bench chargers are quite safe if the directions are read, understood and followed.

In a shop class about 35 years ago I saw the top blown off of a battery so perfectly that it looked like it had been surgically removed. It started out with arcing across the top of the battery while the charger was turned on. I suspect that there was just enough sulfuric acid on the top that it was conducting electricity between the posts. It may have been over filled. Once it blew, it blew the charger’s clamps off of the posts so there was no more arcing. Luckily no one was near enough to be injured by the acid, but it did damage the paint on the wall beside it.

I had a battery blow up when I was younger. Instead of buying a new battery right off, I jump started it one too many times in a short period of time when the gas from an old battery had filled the engine compartment. Fortunately, I always make the ground connection while standing behind the hood. It sounded like a 12 ga and blew acid over the jumper car. I hosed down the finish but obviously not well enough as the paint peeled off in spots the next day. I now just use a jumper battery, wear goggles and rubber gloves. You have a right to be worried. It could cost you your eyesight.
BTW “How close was I to dying?” We are all just an accident away. It can come at any time.

The battery that blew up on us was on slow charge at the time (for about an hour) and the spark was caused when the lousy clamp on the cable popped itself loose; not exactly a first time event. The service manager had balked about a new charger and this incident led him to get another.
The car needed a new battery anyway based on the tests of the electrical system AFTER it was cleaned up and the battery had been swapped out.

The SM was the dullest knife in the SM drawer and a mechanic in the shop had a MAC charger at home (about 200 bucks or so new) that he offered to trade for a 36" center metal lathe in excellent condition along with a box of tooling and the lathe stand that was seldom ever used. The SM amazingly agreed to this and we helped the mechanic load the lathe up.
The mechanic headed off to the motorcycle shop at quitting time and sold it off the back of the pickup for 1100 in cash.

When I was a kid, my father had been having an intermittent no-start problem with his Toronado. The car would be fine, then suddenly just have no electrical power when you turn the key, similar to what a corroded battery terminal would cause. He took the car to the dealership for diagnosis since he couldn’t figure it out. After some head scratching, the dealership diagnosed a battery with an internal fault, I’m guessing a bad connection between cells, though I have no idea. They replaced the battery.

As the mechanic was carrying the old battery across the shop for disposal, it suddenly exploded with no warning that anything was amiss. He was carrying it at about thigh level I guess with one of those strap carriers that connects to the battery posts. (I surmise since I’d seen them carry batteries like this before) I remember the “pop” I heard waiting in the waiting room with my dad. The tech was uninjured except for likely needing a new set of drawers. (and not just from the battery acid)