House battery exploded - alternator voltage?

[sy_Anniina]

Just noticed that one 180Ah battery at house bank had exploded while I was away from the boat - at least did not heat the "kaboom" during our latest cruise.

Luckily only some cleanup and no other damages and/or fire. Not even signs of heat - all plastic parts were just torn, no sign of even thin edges melting.

Checked alternator output (14.2V) as well as mains charger output (14.4V) - these seem well within recommendations. Two other batteries in the same bank seem healthy as well.

A local battery expert speculated that an internal "charging bus bar" could have cracked and caused a spark - leading to small hydrogen explosion.

While the charging voltages seem fine - would anyone have any other suggestion for troubleshooting - or should I just continue with current bank and take the one boom as a single random event?

Tommi

[tiger79]

Sounds like one of those highly unusual one-in-a-million events.  Was the charger connected at the time?

[Lyra]

I assume the charger was connected.
Probably not an explosion, but high rate gassing that burst the casing (this looks like a "no maintenance" without filling/vent caps).
Reason is probably some kind of internal damage (maybe an internal short due to plate shedding?)  that caused excessive current and gassing.

[sy_Anniina]

There are two options regarding the question "charging or not?"

Case 1: If it exploded while I was motoring back to the pier from my latest cruise, I did not hear any "kaboom" but the potential sound was covered by engine noise - and nobody noticed that. (Didn't check that particular locker after leaving the boat). In this case the alternator would have been charging the battery - and back to pier also some heavy intermittent discharging by bow thruster.

Case 2: If it exploded after the cruise - the mains charger was not connected and power was switched off - so no charging or consumption. Internal short as suggested by Lyra sounds possible in this case

[sy_Anniina]

Updating the status of the two other identical batteries connected parallel to the exploded / gassed one...

After cleanup I charged the two other identical batteries in the bank up to normal voltage and everything seemed fine. However, after just two weeks without charging they had self-discharged down to around 2-volt level.

Time to look for new batteries 

[jonrarit]

Thanks for the update. How old were your batteries and were they all the same age? Your episode with the exploding battery and now two others going down would be giving me concern until I found the underlying cause of it all.

While I'm on I've read some "maintanence free" batteries, actually have topping up caps under the labels .... did you happen to notice if the exploded battery had these as you don't often get a chance to see the inside? I've got the same Varta one as your exploded battery ...If it has caps I'd be keen to check the levels if I could.

Thanks

Jonathan

[sy_Anniina]

Update 2:

Tried to charge up the flat batteries - did not work out. After discussing with a local battery re-seller, the most likely scenario is

• first battery has random internal damage (like the bus bar crack) resulting in gassing or small hydrogen bang
• the bang warped the plates of the first battery, creating low-resistance connection or weakish short
• the drain created by the first battery short killed the two other batteries connected parallel

FWIW, my bank was connected in "star pattern" - all pluses to one chunky copper plus bar, all minuses to a minus bar - the plus and minus bars are then connected to consumption and charging.

Maybe my first measurement on the two remaining batteries was by accident while the mains charger was on...

Jonathan - you are correct, the Varta LFD180 batteries I had, do have topping caps under the label. Now that my battery was warm around 35C the label was quite easy to peel from the top of the cap - see attached photos. The level on the two remaining ones for me was OK - so no failure there...

Tommi