Renewable Energy Questions/Discussion > Solar (heating or electric)

Exploding lead acid battery explosion

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off the wall:
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

frackers:
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 :)

oztules:
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

A of J:
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...............

off the wall:
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

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