Last night around 9 PM, we heard what sounded like a gunshot. Went out and looked around. No clues. This morning I see that one of the two 12V batteries on the tongue of my 20 ft trailer had exploded! It's continually being charged by a good quality, computer-controlled converter so It shouldn't have been being over charged. Just yesterday, though I did disconnect the cables one at a time and clean the connections with sandpaper. Then I replaced them, again, one at a time, and greased them so as not to get corroded again. I did this because the batteries were running only 9 volts even though they were connected to the converter for a month. I was figuring they couldn't get charged through the corroded connections.Any clues as to what the problem is?

Shorted cell - boom!Replace the other battery also. Might be eductional to have it load tested but it's toast.

Did you check the water level in the batteries while you had them disconnected? My guess is the exploded one had a low cell and the charging made it spark internally.

How exciting :B Good reminder to wear eye and even face protection around batteries.

A perfectly smart charger will keep trying to fully charge a battery with a bad cell. Eventually, heat builds up and boils what remaining water is in the battery.

I’d also check the converter...regardless of good quality and computer control.

Exploded Battery! | Good Sam Community

CA_Traveler
Explorer III
Oct 28, 2020
Shorted cell - boom!

Replace the other battery also. Might be eductional to have it load tested but it's toast.
opnspaces
Navigator II
Oct 28, 2020
Did you check the water level in the batteries while you had them disconnected? My guess is the exploded one had a low cell and the charging made it spark internally.
time2roll
Nomad
Oct 28, 2020
How exciting :B Good reminder to wear eye and even face protection around batteries.
Super_Dave
Explorer
Oct 28, 2020
A perfectly smart charger will keep trying to fully charge a battery with a bad cell. Eventually, heat builds up and boils what remaining water is in the battery.
Lwiddis
Explorer II
Oct 28, 2020
I’d also check the converter...regardless of good quality and computer control.
Acampingwewillg
Explorer II
Oct 28, 2020
After experiencing the same "ka-boom" myself. I no longer rely of my inverter/charger to maintain batteries. Instead, I use a battery tender now and I don't plug in the RV at all.

I have to concur regarding wearing safety glasses....after seeing the top blown off an 8D battery.
time2roll
Nomad
Oct 28, 2020
9 volts was the clue that the battery was shot.
As long as the cables were off for cleaning... new batteries should have been installed.
Lwiddis
Explorer II
Oct 28, 2020
Time2roll’s counsel is tuff...but accurate. Should have been replaced.
wa8yxm
Explorer III
Oct 28, 2020
One of the big arguments in forums like this is
Which is better
2 six volt in series
or 2 12 in parallel
Well... There are dangers with both hookups and you just found the parallel danger. If one of the batteries develops a shorted cell...or two. the other battery will very rapidely try to charge teh remainingi cells and KABOOM.

NOTE. There are dangers with the two six in series two. I'd rank them roughly equal so the moral of this post is "Whatever occupies your trailer tongue is good" at least up to this point.

I prefer the six volt pairs myself. but that is a topic for a different thread.

Finally.. You need to replace both batteries. and you might think about converting.. WHY? More amp hours for less $$$$ and more still USABLE amp hours.

Down side. More work and taller batteries may not fit.
KD4UPL
Explorer
Oct 29, 2020
A battery at 9 volts is probably bad and should have been replaced. Do you ever check the water in the batteries? I'd bet they ran dry.

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