I have a whole house generator 15/16kw that runs off propane. I do my own maintenance and have changed the oil and filter without issue in the past. I've had this since about 2004 and it's performed like a champ without issue. Well my wife tells me that she noticed it didn't kick on last week Sunday 11/11 for the weekly test. On Tuesday last week I switched the unit from automatic to off so it wouldn't try to kick on in the event of a power outage before I could look at it. Due to numerous issues at home I didn't get a chance to look at it until today. So today I went out to check the oil and it was good. Now when I went to go shut it off last week I noticed that all the LEDs were flashing. I'm pretty sure this means the exerciser has not been set. I do the typical guy thing and say hmm and press the switch to manual (meaning on) and BOOOOM. WTF just happened? It sounded like a double barrel shotgun going off next to my face. My ears were ringing and there was smoke coming off the battery area. After gathering my senses I shut the unit off and started to process of removing my battery.




I've done some internet research and have found that this particular model has some overcharging issues. I'll be contacting Generac this week.

Charging and overcharging generates hydrogen gas. If the water was low in the battery it could have had a nice air and hydrogen mixture inside that was ignited when the generator drew a large amount of current to run the engine starter.

I would be livid.

Damn, I've blown the caps off a bad battery, cracked the case, but I've never seen one go like that. You're lucky you weren't in it's path.

I want to be at Sears when you return the battery.  Figure out when they are the bussiest and go there.  Ask them if this happens a lot?  Hold up a bag full of wer paper towels, and tell them this is as much of the battery acid as I could get.

Having worked for Exide I've seen a number of blown batteries.
Most of them were due to an outside ignition source, usually a cigarette.
Could also be a short causing a spark.

Is it burnt? If not, then it could have burst from gas pressure.
Usually they vent before they do that but it can happen.

If no external source of ignition, and the charging circuit was operating 'normally'...

I'd guess the battery electrolyte got low, battery was gassing aggressively as a result, overheated, and 2 plates shorted...

Resulting in a nice KABOOM.

There isn't much separating the positive and negative plates to start with and a failure from the above condx can easily happen.

A forensic examination of the plates will likely tell the story.

Seen it happen in a car, the guy turned the ignition on and boom, something shorted and ignited the hydrogen.

last month that happened to my neighbors tractor





clean out the battery compartment with something to neutralize the acid


 

Damn, glad you made out of that with out any injuries.

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Not unusual when the electrolyte is low and the battery has some time on it.
I had one let go on me in a well on a boat. Ears still ringing. not good.
I'm lucky the battery wasn't full of acid, A face full of that I don't need.

If the flood has dried out and it's due to gas buildup, there won't be much acid in there anyway.

A good reminder to check/top off flooded batteries a couple times a year with distilled water.

Eggsactly!

Lots of H2 and O2 tho...

Lots of baking soda and water to neutralize. Blow dry with compressed air and/or hair dryer.

Presume low water, lots of H and O2 in the enclosure and then when you tried to start it the spark from the starter's brushes ignited it.

Unfortunately with the prevalence of maintenance free (unmaintainable) batteries in cars, folks tend to forget that many still need maintenance. I even missed this for a while on my truck until I noticed the "eye' on one was dark and then further realized it was not a maintenance free battery. Fortunately it was only a little low so some distilled water fixed it up.

While you don't hear of it much these days, my feeble mind seems to remember this being much more common 35 - 40 years ago.  Seems the most common was explosions when you were connecting jump cables and made the last connection at the dead battery, as opposed to the frame.

If you've got a DMM , that's easy to confirm.

With a good, fully-charged battery installed , the charger will "float" it at around 13.5 volts. Much higher than that, and it's being overcharged.

Let me guess.

1. " Whole house generator " has a float charger that didn't " float " properly and has been cooking the crap out of the battery.
2. Hydrogen gas and a nice mix of oxygen are contained in the battery compartment.
3. Due to the excessive corrosion on the battery terminal - it is possible it sparked there, at the positive terminal - close enough to light off 4 of the 6 cells.

eta: check the second photo for the thick build up of corrosion, just below where the terminal clamp was.  This has been building up for quite some time.

eta again:  If the positive terminal was not making " GOOD " contact to begin with ( due to excessive corrosion ), the float charger would not shut down as designed, and would continue to charge.
Overcharging would cause the water in the electrolyte to cook off - thereby creating more hydrogen gas.  
Ignition spark was at the positive terminal when he applied a load to the system.