Author Topic: Exploding lead acid battery explosion  (Read 3043 times)

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Offline off the wall

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Exploding lead acid battery explosion
« on: April 11, 2015, 05:25:56 PM »
I have been testing capacity of a bank of lead acid batteries for someone. In fact a major problem is the insulated connectors which are bolts not of stainless steel but of galvanised iron, which sit upon a 1mm ring of copper attached to the connectors and buried in insulation, and which need tough screwing down to make proper contact. But that's not the problem today . . .

It's a 1000ah bank of batteries and after a full charge I took out 600ah down to around 11 volts. Sun has not been brilliant in England so whether they've had 10 days of 12 amps or so for 6 hours is a moot point and the batteries have been gassing nicely at around 28.5volts during charges with the specific intention of equalising them. Some show specific gravity at full charge density whilst a few are still lagging behind a bit.

During charging today, we were connecting together another row of batteries adjacent. There was no circuit made, merely inserting the interconnecting links. Perhaps this caused some vibration.

Without the presence of a spark two batteries in the centre of the bank exploded, rupturing the top four inches of the casing and spilling a considerable quantity of acid on the floor.

I can only think that the caps which should be capable of allowing gas to exit simply didn't do so, allowing undue pressure to build up.

Has anyone had any experience in this sort of direction?

Best wishes

OTW

Offline frackers

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Re: Exploding lead acid battery explosion
« Reply #1 on: April 12, 2015, 12:31:15 AM »
My experience of lead acid batteries exploding is a very loud bang (12 gauge volume) as the gases (in the perfect ratio!!) burn. Overpressure I'm sure would be more of a pop and less spray of acid (if that can be determined after the leak).

I'm now restricting my use of an angle grinder to just setting my trousers on fire :)


Robin Down Under (or are you Up Over!)

Offline oztules

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Re: Exploding lead acid battery explosion
« Reply #2 on: April 12, 2015, 09:01:37 AM »
I'm with Frackers on this one..... the stoichiometric conditions in the cell are ripe for explosion...not a pop.

Somehow an ignition source has turned up, maybe a fracture in the plate to collector or something, but a pressure response will be a whole lot less energetic than a nice explosion of one of the fastest burning gasses there is.

Been there and done that a few times with industrial traction machines from time to time...... the noise is a very serious crack... has a sound barrier feel about it. Frackers description is apt.

Ditto on the angle grinder, although I also include my windcheater in that.



...............oztules
Flinders Island...... Australia

Offline A of J

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Re: Exploding lead acid battery explosion
« Reply #3 on: April 13, 2015, 09:30:11 PM »
It's a 1000ah bank of batteries and after a full charge I took out 600ah down to around 11 volts. Sun has not been brilliant in England so whether they've had 10 days of 12 amps or so for 6 hours is a moot point and the batteries have been gassing nicely at around 28.5volts during charges with the specific intention of equalising them. Some show specific gravity at full charge density whilst a few are still lagging behind a bit.

Something does not quite add up here, a 1000ah bank receiving 12A for 6 hours/day over 10 days? Then discharging down to 11V for an apparently 24v bank?

Is this a 12v bank or 24v bank?

Almost sounds like a 12v bank has been supercharged to 28.5V if that is possible, and two batteries have protested.

Nah every which way I look at this there is some miss information. Were the batteries gassing with only solar input? or...............

Offline off the wall

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Re: Exploding lead acid battery explosion
« Reply #4 on: April 14, 2015, 02:57:58 AM »
Hi!

Sorry - I think of a 12V system with the 11-14V range as standard - so there is a typo in the above - I discharged down to 22V - (being the 11V equivalent) so there's no anomaly.

I have been hosting over the past couple of days a meeting in England focussing on battery charging and rejuvenation.

Some time ago I sold an inverter to someone setting up tea rooms by a lake without grid power. He's finally got the grid connected and so he sold me his battery bank. This is a 48V bank of batteries, again 1000ah, and although shorter and fatter than the bank which suffered the explosion, bear similarities. I have yet to look at the specific similarities of castings, but the plate separators are the same plastic material inserted in the same way, and the cases are the same plastic material and colour but with a different colour vent cap. Three cells had been rejected and replaced by (OUCH) 600ah cells - and the retailer who recommended that needs to be shot. The "dead" cells were given to me in addition, and presented a 1.5V reading. Why they were dead we don't know.

For fun, we connected the dead cells to a rejuvenating charger over night, and this brought the three cells up to 2V, 1.9V and 2.1V. At lunchtime yesterday I presented to them a 12V incandescent bulb and on 2V cell caused it to glow dimly, the 1.9V just slightly less strongly and the other 2V cell at first not at all and then nearly as the others. Specific gravity was at the low charge end of the scale. We connected the charger to the three cells over lunch covering the cells with plastic and underneath a table. We went off to lunch and within 10 minutes an assistant nearby to the workshop reported an explosion . . .

This was another situation where there was no external spark and where gas was ignited internally. What by? Upon inspection there is no obvious cause and this is worrying.

Interestingly the second exploded cell is showing the top of one of the plates and the plates are quite thin . . . and a grid containing paste. I thought that this construction was only used for car batteries and not deep cycle batteries.

These battery banks were reported to have been bought "cheaply" and are without manufacturer markings nor ratings indications - and I suspect that there is a flood of them on the market in England, probably imported from China.

Clearly they should only be used in a situation that provides for acid containment, well vented and possibly with the vent caps open, although an ignition of one could then spread to any other gassing cells.

Best wishes

OTW

Offline MadScientist267

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Re: Exploding lead acid battery explosion
« Reply #5 on: April 14, 2015, 03:18:09 AM »
OTW -

A second explosion? It's time to reevaluate *something* from the sound of it. While you could theoretically get just so unlucky, the likelihood of two independent and unrelated events near back to back like that is less than nil.

At the very least, buy out 3 stores worth of baking soda and maybe get a fire truck on standby (couple birds with one stone?) until you have checked, rechecked, and checked everything again for any possible connections between the two events. And above all else, keep yourself and anyone else safe in the process!

Good luck... I hope a reasonable explanation comes to light before something else happens :-\

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline off the wall

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Re: Exploding lead acid battery explosion
« Reply #6 on: April 14, 2015, 03:57:06 AM »
Dear Steve

Thanks

I do assure you that the thing in common with both explosions, apart from charging at 12 amps - clearly don't ever ever ever charge 1000ah batteries at 12 amps ever - is cells bought cheaply on the UK market in black and grey cases with neither manufacturer's marking nor capacity identification.

The second explosion was "achieved" with wholly different equipment. The first was a charge from my solar system charging on 12 amps togather with other banks of batteries in parallel at the same time, the other batteries having the same charging regimes for two years. The second was on a dedicating recycling monitoring charger which desulphates and charges on a monitored basis.

Best wishes

OTW

Offline rossw

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Re: Exploding lead acid battery explosion
« Reply #7 on: April 14, 2015, 04:09:50 AM »
clearly don't ever ever ever charge 1000ah batteries at 12 amps ever

Are you suggesting that this is too much, or too little current?

If "too much", I can't believe that C/100 is "too much", and for 10 years I've run typically C/10 and higher (500AH and 1000AH banks at 50-80A charge).

If "too little", I can't believe that they require more than that, and for 10 years when sun has been less than great, significantly less than 12A for hours on end has been common.

As Steve says, I suspect that there's something else at play - even if its only "dumb luck".... but I have great doubts that 12A charge for a 1000AH bank is "bad" (except for probably being not enough!)

Offline A of J

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Re: Exploding lead acid battery explosion
« Reply #8 on: April 14, 2015, 04:10:20 AM »
Allan tips his hat and bids this thread a duh, confusion reigns.

Offline off the wall

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Re: Exploding lead acid battery explosion
« Reply #9 on: April 14, 2015, 04:31:19 AM »
clearly don't ever ever ever charge 1000ah batteries at 12 amps ever

Are you suggesting that this is too much, or too little current?

Apologies. My sense of humour - to demonstrate that there was nothing unreasonable about how these batteries were being treated. There is some capability of this design of battery to self ignite gas internally.

ila_renderedila_renderedila_rendered

What I believe to be in common is a cheap and poorly made battery with a design or manufacturing flaw.

The two batteries have in common the same plastic plate separators and clearly come from the same stable.

Best wishes

OTW

Offline A of J

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Re: Exploding lead acid battery explosion
« Reply #10 on: April 14, 2015, 08:39:02 AM »
Johny cool pants reborn?

Offline off the wall

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Re: Exploding lead acid battery explosion
« Reply #11 on: April 14, 2015, 12:51:52 PM »
Here are the photos of the other similar cell which exploded.

ila_renderedila_renderedila_renderedila_rendered

Best wishes

OTW

Offline A of J

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Re: Exploding lead acid battery explosion
« Reply #12 on: April 14, 2015, 04:02:04 PM »
It seems to me that you may be using a charger that has a high voltage pulse, if this is the case then bin it, the battery construction may be "cheep" , hard to say but looks fairly standard to me. Batteries can and do short out internally but in my experience this does not cause an explosion

I worked for 27 years in the power industry where the generators are filled with hydrogen (as a cooling medium), explosive limits for hydrogen are 4-74% in air, much more in a oxygen rich environment. Leaving the caps in place ensures a hydrogen rich mixture in the battery, should an ignition source ignite venting gas then the flame should stay external to the battery.

Can you please define over what period of time you discharged 600 ah, and how you measured/ achieved this this?

In one of your pics of your handy work (sorry my sense of humor) I see what looks like 4mm sq wire and both red (a recipe for confusion and disaster), this goes to the above question. What are you using these batteries for or are you just using them as a learning experience? There are lots of outcomes here, just whether they have been a learning experience remains to be seen, or maybe not. 

You stated that the bolts were not stainless steel, in one of your pics, the one where we see the red trolly, that remaining bolt look stainless steel to me.


Offline MadScientist267

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Re: Exploding lead acid battery explosion
« Reply #13 on: April 14, 2015, 04:38:04 PM »
Going by other clues, the cell in the second set of pics also looks like it may possibly be swollen,  indicating extra stress on the separators, potentially leading to an internal short (closely following gassing, this could easily lead to an explosion)... It's hard to tell exactly tho because of the vantage point of the pics.

The first cell doesn't seem as cramped inside, but as A of J mentioned, there are other issues that potentially could have caused the demise of that one.

Lead Acid isn't a toy, and particularly when you get up into the larger cells. The potential for disaster increases notably as size goes up. Use proper wiring, terminators, etc or this type of thing might be a regular occurrence. I'm not saying explicitly that either or both are your fault, but it's difficult to rule that out going by the pics.

You've seen what they can do to themselves, please know that it can (and does) get worse from there. Imagine the top of that cell being the ceiling of a battery room... Google has a fair collection of pics illustrating the latter. None of them are pleasant scenes.

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline off the wall

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Re: Exploding lead acid battery explosion
« Reply #14 on: April 14, 2015, 04:55:09 PM »
Thanks

I have been managing a 300kWatthour battery bank now for a couple of years and so am not a complete newbie when it comes to batteries, but am somewhat perplexed by the experience.

My own personal battery bank is colour coded red for positive and black for negative, arranged in switched banks, fused and arranged using with connecting wire and bus bars appropriate to expected currents, fuse ratings and out of preference I like stainless steel connecting bolts and washers.

One of the major reasons for failure in my experience of banks of traction batteries is the insulated bolts clamping down on a 1mm ring of metal resulting in a good recipe for bad contacts: I'm aware of these sorts of issues and for that reason in testing this bank I replaced them by stainless steel and ensuring good contact with connecting wires held securely by washers.

The first cell that blew was in a bank that someone asked me to look at. Its major problem had been poor connections. I charged it as one of the subsections of my battery bank on which the charging currents per section are not much more than a ball park of 12 to 15 amps maximum. For this connexion with 6mm cable is perfectly adequate. For discharge as a test load I have a 22V to 30V 600W grid tie inverter which from a 24V battery bank on a continuous basis puts a constant 500W into the grid, so discharge at 20 amps. No-one can say that a C50 rate is mis-use of a battery . . .

That discharge to 22V was a few weeks ago and from memory it was over 30 hours, thus 600ah

On the day that the cell blew, there was good sun, giving a 12 amp charging rate at around 28Volts which should be fine even if overcharged as an equalising charge . . . and as you say with the caps on, the hydrogen concentration should not have led to ignition, but there was ignition from some source inside the cell and the explosion was violent. The explosion was internal and not external.

With regard to the second cell which blew under a desulphation charge the specialist charger used, developed by someone in the battery business for over 20 years, does not use a high voltage pulsing regime. It so happened that the developer of that charger was here and it was he who had set up the three cells to be charged. The sources of ignition were internal rather than external and it's for that reason that this is of particular concern. Were an identifiable cause in terms of a loose wire, external spark to have caused an external explosion, those are comprehensible circumstances.

Best wishes

OTW