Battery EXPLOSION RISKS !

[JumbleDuck]

That's wrong, batteries will explode due to hydrogen being present.

Been there, got the tee shirt (full of holes from when the battery exploded), real World experience. Back in the early 70's when i was training as a mechanic, i was asked to take a battery off charge. No-one mentioned turning the charger off first. Old style battery, old style charger, been gently bubbling away all night, fitted to a car. When i removed the crocodile clips from the terminals there was a spark and the battery exploded in my face. Bits of battery went all over the place, as did the acid. I was very lucky to escape without injury.

With all due respect, that doesn't mean that the explosion was due to hydrogen. Battery chemistry ain't my thing, but it may be that a brief hydrogen burn touches off something more powerful.

 

[MikeBz]

It's an interesting article, although as ever one needs to remember that Nigel Calder is an interested amateur. However, it doesn't say anything about loose terminals causing thermal runaway. Perhaps they encourage some chargers to apply to great a voltage in order to get a specified current flowing.

That could only happen if the charger has no voltage limit - so it would happen as the batteries approached full charge anyway. Also if a poor connection requires a higher than normal voltage to get the required current then there must be a voltage drop across the poor connection, so the battery won't be seeing the high voltage anyway.

One thing I take away from this discussion is that if the temperature sensor is effectively a safety item to stop or reduce charging if a battery temperature gets out of hand then there needs to be a sensor on every battery in the bank. But can if you parallel them (the sensors) up does charger see the highest temperature?

 

[GregOddity]

That could only happen if the charger has no voltage limit - so it would happen as the batteries approached full charge anyway. Also if a poor connection requires a higher than normal voltage to get the required current then there must be a voltage drop across the poor connection, so the battery won't be seeing the high voltage anyway.

One thing I take away from this discussion is that if the temperature sensor is effectively a safety item to stop or reduce charging if a battery temperature gets out of hand then there needs to be a sensor on every battery in the bank. But can if you parallel them (the sensors) up does charger see the highest temperature?

Very good point about the sensor. Very good question as well. Got no clue as to the answer tho but sure would like to know.

 

[lw395]

With all due respect, that doesn't mean that the explosion was due to hydrogen. Battery chemistry ain't my thing, but it may be that a brief hydrogen burn touches off something more powerful.

Exactly.
The hydrogen is like a detonator.
I was hoping to point out there are other ways of setting off the main explosion.

The point is, I wouldn't mess about with overheated batteries, even if you've stopped the charging and vented the hydrogen.
If the case has gone soft enough for the plates to contact as you lift it, BANG!

One of the really stupid things I got away with in my youth, I had a rusty old car, the battery carrier fell apart to the point where the battery case was starting to touch the exhaust manifold.

 

[PaulRainbow]

Exactly.
The hydrogen is like a detonator.
I was hoping to point out there are other ways of setting off the main explosion.

The point is, I wouldn't mess about with overheated batteries, even if you've stopped the charging and vented the hydrogen.
If the case has gone soft enough for the plates to contact as you lift it, BANG!

One of the really stupid things I got away with in my youth, I had a rusty old car, the battery carrier fell apart to the point where the battery case was starting to touch the exhaust manifold.

What is it detonating ?

 

[lw395]

What is it detonating ?

A few mega joules of stored chemical energy.
I've just worked out that a 100Ah times 12V is equivalent to a kg of TNT.
Somebody else do the sums:
TNT equivalent - Wikipedia

 

[Lucy52]

Musing only. Does an explosion not involve a plasma which can conduct electricity which could then short out the battery terminals?

 

[JumbleDuck]

That could only happen if the charger has no voltage limit - so it would happen as the batteries approached full charge anyway. Also if a poor connection requires a higher than normal voltage to get the required current then there must be a voltage drop across the poor connection, so the battery won't be seeing the high voltage anyway.

I'm thinking of my experience with my DS (mentioned above) when a Lidl/Aldi type charger cheerfully ignored the high voltage needed and kept on pushing 3.8A through a dud battery until the failed cell was completely dry.

 

[Bilgediver]

I suspect that internal short and spark plus the the accumulation of hydrogen and sulfuric gases inside the battery would be the most probable cause.

That was what I was thinking . I am pretty sure the timeline was so short that it wasn't a heat issue.

 

[JumbleDuck]

What is it detonating ?

Detonation is when an explosion propagates by shock and the flame front propagates at the speed of sound or higher. Sometimes much higher: 2000m/s is quite typical.

Deflagration is where combustion (not an explosion) propagates thermally and the flame front moves slower than the speed of sound. Hydrogen-oxygen mixtures deflagrate.

Black powder deflagrates but TNT and dynamite detonate. A detonator is a small charge which starts the shock wave needed to start the large charge when simple heating witha fuse won't have any effect.

 

[GregOddity]

It's interesting to note the how hard it is to find some literature on the matter.

Here's some interesting links.

https://www.eaton.com/content/dam/e...resources/Eaton-Battery-Handbook-BAT11LTA.pdf

Thermal runaway

 

[Graham376]

As a matter of interest, what have people done to safeguard batteries in the case of extended lock down?

As we charge by solar and are most likely looking at a couple of months before allowed back, I've reduced absorption time and voltage and topped them well up.

 

[JumbleDuck]

As a matter of interest, what have people done to safeguard batteries in the case of extended lock down?

As we charge by solar and are most likely looking at a couple of months before allowed back, I've reduced absorption time and voltage and topped them well up.

I checked that mine were both properly charged when I went round the boat at the weekend. They are currently charged by a single rather opaquified 50W panel through a Photonic Universe dual battery PWM controller which has been very reliable so far. So basically I have fairly new batteries getting a small amount of charge through a proven system, which I think is as good as I'll get it.

Also, I'm insured ...

 

[Graham376]

I checked that mine were both properly charged when I went round the boat at the weekend. They are currently charged by a single rather opaquified 50W panel through a Photonic Universe dual battery PWM controller which has been very reliable so far. So basically I have fairly new batteries getting a small amount of charge through a proven system, which I think is as good as I'll get it.

Also, I'm insured ...

I'm insured for fire but not for £600 of knackered batteries due to overcharging and loss of water.

 

[rotrax]

Some of you without direct experience are totally missing the point here.

Of course there is substantial energy stored in a battery, but it is a scientific fact that hydrogen mixed with a specific quantity of air burns very fast.

Getting that dramatic and fast expansion out of a confined space will cause the battery case to rupture.

The internal contents will come out.

Which is what I have witnessed on more than one occasion.

 

[JumbleDuck]

Some of you without direct experience are totally missing the point here.

Of course there is substantial energy stored in a battery, but it is a scientific fact that hydrogen mixed with a specific quantity of air burns very fast.

Getting that dramatic and fast expansion out of a confined space will cause the battery case to rupture.

The internal contents will come out.

Which is what I have witnessed on more than one occasion.

If you set fire to a balloon full of hydrogen and oxygen you get a nice big bang and a whoomf of flame, but little or no expansion - it all burns away where the balloon was. I am sue you have seen batteries go bang; it just seems unlikely that the small free space atthe top of one could contain enough hydrogen to have any significant effect. Perhaps being stored under pressure helps.

 

[rotrax]

If you set fire to a balloon full of hydrogen and oxygen you get a nice big bang and a whoomf of flame, but little or no expansion - it all burns away where the balloon was. I am sue you have seen batteries go bang; it just seems unlikely that the small free space atthe top of one could contain enough hydrogen to have any significant effect. Perhaps being stored under pressure helps.

But in a battery that energy is retained until the weakest part of the container ruptures. A balloon just stretches until it bursts.

On the old fashioned flooded cell lead acid batteries, the case was a hard synthetic rubber, divided into three or six compartments. The plates and dividers were inserted with external inter cell lead connecting bars and the top sealed with a pitch type substance.

In my direct experience this soft pitch like substance was the first to give way, the top then lifting off and chucking acid around. Nasty.

Yuasa types were made of a special tough plastic, inter cell connectors under the heat welded on top. The vent was a 3mm bored hole in a right angle plug in one end of the battery, to which a plastic tube was affixed allowing gasses to escape. When one of these suffered a hydrogen burn the plastic case burst and the right angle end plug could be fired out quite easily by the rapid expansion.

I also have some experience of Black Powder. Put an ounce on a paving slab, light it, bit of a puff and a flash as it burns off.

Restrict its expansion - as in a muzzle loading gun - and you get a burn fast enough to throw a lead ball significant distance.

As you say, it is the pressure build up as the only escape is from the battery vent system. These are easily blocked with dirt or the vent tubes pinched by poor fitting.

Simples..................................

PS - After further thought - it was a long time ago that I studied Boyles Law - a petrol air mixture of 15:1 will burn quite fast. Enough to make a nasty pop in an open container.

Compress it inside a closed cylinder and ignite it and it does real work.

It makes cars go along...........................

 

[JumbleDuck]

But in a battery that energy is retained until the weakest part of the container ruptures. A balloon just stretches until it bursts.

I used to light the balloons with a candle. The balloon burns faster than the gases inside burn, so you get a nice balloon-shaped flame and bang where it used to be.

PS - After further thought - it was a long time ago that I studied Boyles Law - a petrol air mixture of 15:1 will burn quite fast. Enough to make a nasty pop in an open container.

Compress it inside a closed cylinder and ignite it and it does real work.

It makes cars go along...........................

It only makes cars go along if you do it a hundred times per second.

 

[rotrax]

I used to light the balloons with a candle. The balloon burns faster than the gases inside burn, so you get a nice balloon-shaped flame and bang where it used to be.




It only makes cars go along if you do it a hundred times per second.

At my school, before the chemistry double period immediately after lunch on a Friday, and obviously before the Teacher entered, we would fill condoms with a mixture of coal gas - from the bunsen burner taps on each bench - and air, by blowing into them. We would knot them and light the tail. Set free out of the window they would float away on the wind and make a satisfying bang when the gas exploded.

 

[Graham376]

At my school, before the chemistry double period immediately after lunch on a Friday, and obviously before the Teacher entered, we would fill condoms with a mixture of coal gas - from the bunsen burner taps on each bench - and air, by blowing into them. We would knot them and light the tail. Set free out of the window they would float away on the wind and make a satisfying bang when the gas exploded.

After my father died, I found he had kept all my school reports, not good reading. Mr Leach (known as Dracula) our chemistry teacher, commented term after term "apparently only interested in explosive compounds"