Burned batteries.

D

desertqueen

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Thankfully this is not something you get to see every day, and I wanted to share it for the people who have a casual attitude about DC. These were on my dock this week; I asked the dock master about them but he hasn't heard back from the owner yet. The one on the right looks like a maintenance-free lead acid that got overcharged.

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[ QUOTE ]
The one on the right looks like a maintenance-free lead acid that got overcharged.

[/ QUOTE ]The two batteries are identical, aren't they?
 
Strewth!
It looks like fire rather than explosion though, a mate of mine once had a motorbike battery explode, luckily there was not much in the way, but it threw acid all over his dad's (company) car!
I had a lucky escape when the battery holder on an old car rusted out, dumping the battery onto the manifold!
I wonder if the batteries in the picture were charged at high rate with low electrolyte levels?

Sobering!
 
Both positive terminals are undamaged, burnt out neg cable ? burt / melted battery case ?

Fault on badly damaged one, bad connection possibly, cable caught fire, burning across to other battery so not damaged as much.

Could be a lowish current fault, so fuse would not have helped.

Brian
 
Are you likely to find out what happened?

If so, please post. It's good to learn from other people's mistakes, but only works when we know exactly what the mistakes were.
 
OK - here's my theory: The batteries were connected in parallel. Not uncommon for people to connect them in this way rather than go to the bother of having a switch and selecting one at a time, as required.

Suppose a cell in one battery fails resulting in a short circuit. Normally failing cells just get high internal resistance but I believe it's possible for them to short if the plates get distorted or start to flake.

So now we have a 12v battery in parallel with a 10v battery! Ouch - unbalance in the EMFs will cause current to flow between the batteries. The internal resistance of batteries is designed to be very low so the current is likely to be very high indeed! Result - both batteries get hotter and hotter and....

Any battery experts out there who can comment on this - maybe shoot me down? Is it likely? Should we be cautious about parallelling up 12v batteries in boats?
 
[ QUOTE ]
Should we be cautious about parallelling up 12v batteries in boats?

[/ QUOTE ]So what alternative do you suggest? I have 6 x 110Ah batteries parallelled, how would you improve that?
 
[ QUOTE ]
OK - here's my theory:

Suppose a cell in one battery fails resulting in a short circuit. - both batteries get hotter and hotter and....

[/ QUOTE ]

You would overheat the battery top generally.

Back in the late 1980's / early 1990's Sealine had a batch of batteries that had intermittant shorted out cell. Came to light on a 365, batteries had blackened tops, and we thought it was a fault on our mains charger. But we changed the charger and took it back for test, no fault. Next we thought it may be related to the large rotory inverter fitted, but no. We spent the day running the system no fault. Met the engineer who looked after the boat, and he promised that it did overheat.
So back to the battery manufacture, and they finally agreed that there was a battery fault, the cell link when it got hot could short out a cell. By shorting out the cell it caused overheating, thus keeping the short. When turned off link returned to normal, away went the short, battery now back to 12 volt, no fault visiable.

So short answer it can happen, but not what you see. This looks more like a cable fire.

Brian
 
I don't think that the energy that caused the damage came from the batteries. There is far too much damage after the stage at which the batteries would still have been delivering power and the effect is too localised. I think that the batteries lost electrolyte (probably gassing and failure to top-up as they look like flooded lead acids) then power coming from a mains-powered battery charger.

Moral:-- Keep your batteries topped up and leave your charger on only if you know that the batteries are topped-up!
 
[ QUOTE ]
[ QUOTE ]
Should we be cautious about parallelling up 12v batteries in boats?

[/ QUOTE ]So what alternative do you suggest? I have 6 x 110Ah batteries parallelled, how would you improve that?

[/ QUOTE ]I don't have a practical alternative. It's probably an unusual fault anyway. It would be a [--word removed--] if it happened though, wouldn't it?
 
I would say this is the result of a very low resistance external short circuit resulting in battery currents of hundreds of amps producing internal heat far too quickly to disipate. You would need an impossibly large charger to do this.

I once investigated a nice short circuit. It was a newly installed data centre standby battery - 460volts 250Ah. It was all connected up with the dry charged cells and parallel cables through an underground duct to the load. They filled the first 229 cells with acid then started pouring it into the last one and all hell was let loose - flames, smoke and boiling acid all over the place. The two sets of cables had got mixed in the duct before going onto the terminal posts so they actually had a dead short on the battery. That got me a nice trip to Indonesia away from the winter!

Another one was a 48V 2200Ah (yes, 2200) in Abu Dhabi. A large spanner got dropped across the main busbars. The spanner melted. The spark ignited gas (the battery was being boost charged at the time) and several cells the size of dustbins exploded. There were shards of 1cm thick plastic from the containers stuck through the plasterboard ceiling.

Batteries can be dangerous becuase of the huge currents they can give!

Mike /forums/images/graemlins/laugh.gif
 
[ QUOTE ]
The two batteries are identical, aren't they?

[/ QUOTE ]
You are absolutely correct! I had another look at them this morning and they have a common vented cap for all of the cells together. (My batteries' cells have individual caps.) The one battery is just missing it's cap, and the other I couldn't get off to check for sure because it is melted onto the battery.
 
[ QUOTE ]
Are you likely to find out what happened?
If so, please post. It's good to learn from other people's mistakes, but only works when we know exactly what the mistakes were.

[/ QUOTE ]
When the marina office opens this morning I'll stop to ask if they've heard from the owner yet. Yes, this is definitely a mistake that doesn't need repeating! My guess is that the batteries were on a charger and the cells dried out.
 
D
I agree, I had a small 40 ah battery on charge with my simple wack it to it charger, I forgot it and when I checked 2 days later it looked exactly the same.
Stu
 
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