I've had a Harbor Freight float charger on my vehicle that I rarely drive for the last few years. I went to start it on Tuesday and when I turned the ignition I heard a huge BOOM under the hood and smoke started pouring out. I popped the hood and saw the battery had exploded and there were pieces of plastic around the engine and acid flowing into the battery tray. I removed the battery, picked up the plastic pieces, and pulled the tray. I sprayed water with baking soda over the acid and installed a new battery. Fortunately the car seems fine. I'm not sure if the battery just ran out of water or the HF charger overcharged it. I'm thinking about buying a "battery tender" float charger as they seem to get good reviews though the HF charger worked fine until this incident.

The only time I've seen one explode is left on a high charge rate for too long. I had a 6 volt battery on a slow charge one time and forgot. When I remembered hours later I could hear it boiling inside. I unplugged charger from a distance cause I wasn't going anywhere near that battery to unhook it. Throw that HF charger in the garbage and get a Shumacher charger. they are the gold standard IMO. Walmart sells a Shumacher battery tender for around $ 25 that I've used for years to charge trailer batteries and the kids power wheels battery. I have the roll around model for my shop though.

gases build up under the hood from charging the battery is the vehicle parked where you can leave the hood up?

Ed

I had one blow up at work while starting an engine about 10 years ago. Near as I can tell the battery was probably low on water. No charger involved at all.

The plates can bend and touch each other inside the battery under a big load like cranking an engine. A spark inside the battery makes a big boom!

Regarding chargers, I stopped using my old school charger and got one that will shut off when the battery is charged. That old school one killed an expensive gel battery in my cycle when I left it on too long.

No experience with a battery tender here.

Hydrogen gas filled your engine compartment....I use a charger with a timer...won't over cook a bakery that way...

I think I figured out what happened. I checked my boat battery and discovered the water level was too low. Leaving the battery to be constantly charged evaporated the water below the plates which allowed a spark to ignite the hydrogen. So I guess the moral of the story is to keep an eye on the water level if you are using a float charger.

Also use ONLY distilled water when you add it. Tap or spring water always has minerals that will shorten the battery life, especially iron. Distilled water is cheap and every grocery store has it so use it. The old saying that if the water is safe to drink, it's ok for the battery is crap. It keeps battery makers in business.

Yes, you are correct. I was assuming that was common knowledge but thanks for the reminder.

Distilled water is common knowledge among those who know anything with batteries but there are lots of people who don't.