Almost went boom

[Javelin]

Popped across to the boat today to give it a quick sponge out.
There's been a lot of rain the last week or so and being keel stepped there's always a little water that gets in at the shroud t terminals and gets into the bilge.
Decided to run the engine for some heat but hmmm, that's strange the battery seems flat.
Checked below and the mmpt reg says 7.4v but the panels were charging at 4.6v
Multi meter out and all five batteries were below 8 volts.

Grabbed the jump starter from the yard and fired up the engine but it was only charging at 12.4v and not the usual 13.4v.
Ran out an extra stern line and put her in gear and ran her at 2k and hoped that things would improve.
They didn't, in fact the charge voltage went down to 11.4v which was really strange.
Lifted starboard battery access and all seemed fine with the three bats that side.
Lifted up Port access hatch after about half an hour of moving all my sails etc which I'd heaped on top of it.
Dammed glad I did as when I lifted the hatch firstly the rotten eggs smell hit me and the very last battery in line was hot to the touch.
Shut everything down, very carefully disconnected all the bats and gingerly removed the, by now, very hot, angry 120a house battery, off the boat and onto the pontoon.
Went back to the boat, tidied up and an hour or two later checked on the battery which despite the -1 air temp was still hot to touch.
Have had a blazing head ache all evening due to the fumes it gave off in the boat.

Considering myself very lucky it didn't all go boom.

Makes you wonder what you can do to spot this kind of thing earlier.

 

[Champagne Murphy]

Well done, that could have been very nasty.

 

[Old Harry]

A tough call , moving a hot battery is very risky , i hope the rest recover ok
Do leave the charger on 24/7 un attended.

 

[matthewriches]

Should of been posted in the PBO forum following on with the requirement of a 20 page "discussion" :hopeless:

But here in the East Coast Forum, we are much more civilised

I think you need a low voltage alarm that maybe sends you a text if the batteries were to get seriously low. I say seriously low to avoid nuisance notifications, maybe as low as 10 or 11v.

 

[PaulRainbow]

Very risky disconnecting the batteries under those conditions Mike, glad it went OK for you. A battery monitor or volt meter with built in low/high voltage alarms would alert you to a problem, but unless you're onboard you won't hear it. Where your boat is moored you'd have to have something to send you a text or maybe a light wired to the alarm so you can see it from the yard.

A couple of points though, 13.4v is low for the alternator, that'll never fully charge the batteries, and how have you got the batteries connected that they are all dragged down to nothing by one dead battery ?

 

[Champagne Murphy]

Very risky disconnecting the batteries under those conditions Mike, glad it went OK for you

For future reference and in the spirit of life preservation, how else?

 

[Keith 66]

Best to shut every thing off & ventilate, I saw a big battery explode years ago, a spark from the terminal was all it took. bits everywhere & the guy who was disconnecting it splashed with acid. Lucky that he didnt get any in his eyes, there was a tap nearby & he was able to hose himself down very quickly.

 

[Leighb]

Do you have a gas alarm? Mine certainly triggered when one of my house batteries went the same way. I came down to the boat to remove one or two personal things a few days before hand over to the new owner and heard the alarm going, went on board and was met by the rotten egg pong!!

I just opened all the hatches and went off to get new batteries but the smell persisted for a day or two even with lots of ventilation. Luckily gone before he took over the boat, I did tell him what had happened though.

 

[PaulRainbow]

For future reference and in the spirit of life preservation, how else?

The hydrogen is explosive and removing battery cables can cause a spark.....boom ! I have personal experience of this, it isn't nice. I once had one explode right in my face, covering me with acid. As above, very lucky it didn't get in my eyes and there was a tap close by.

Ideally, remove all charging sources, vent the gas and come back later. Whatever you do, avoid mixing hydrogen and sparks.

Knowing Javelin, i imagine he took some precautions.

 

[PaulRainbow]

Do you have a gas alarm?

Co alarms often go off in the presence of hydrogen.

 

[pyrojames]

Unfortunately your u need to get the failed one disconnected from the others, otherwise they will continue to dump power through it. I had one go and then put it on a rope and hung it over the side with the terminals above the water. Two reasons, one to cool and the other to disperse the acid safely should it have ruptured.

I now have banks 6v Trojan’s in series, and paralleled by switching rather than multiple 12v in parallel, so that a single failure wont result in other battery trying to discharge through the failed one.