Author Topic: Exploding lead acid battery explosion  (Read 3275 times)

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Offline A of J

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Re: Exploding lead acid battery explosion
« Reply #15 on: April 14, 2015, 05:12:49 PM »
And here is one pic to start you off.............
ila_rendered

That was taken from this artical http://www.daintree-holidays.com.au/daintree-pollution.htm, if you read it take it with a grain of salt. I have lived here for just short of 4 years using solar and I have an air conditioned house, cook off electricity etc. The pic is from before I moved to this area. This to me is a classic example of a wiring fault, perhaps even the connection at the lead flapping in the breeze, an overheated/shorting/melting wire or joint is not your friend.

Just as interest I will give you another example of wiring faults, not batteries directly but part of the system. While visiting the home of an acquaintance and looking over the top of a shot of home-brew rum or was that several, I noticed his DC switchboard open and smoke trail, and charred wires.  He told me it caught fire, the battery fuses blew, wires caught fire and his pl40 was no longer working.

I went back another day to effect repairs, now it is hard to get the true story sometimes but battery fuses blew, so a well meaning local chap bypassed this fault, somewhere this same chap extended the wires from the solar panels to the controller by about 200mm (8"). One connection is not tight, a blue point connector that was not flame proof was used and caught fire. Since the owner was home it did not result in a house fire, most of our homes up here are timber, ceder lined in and out. There are many house fires, I can only postulate as to how these fires occure.

Offline oztules

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Re: Exploding lead acid battery explosion
« Reply #16 on: April 14, 2015, 10:05:39 PM »
"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."

For the sake of completeness it is important to understand that the mixture in the cell has more oxidant in it than hydrogen.... simply because of the lightness of the H2 gas.

However, in an oxygen rich environment you only need 4% to be hydrogen, and it will detonate... not just burn.

So it is not true that a leak will/may have flame on the outside, and not progress into the cell from venting gas..... it will.... have no doubt at all..

It is not like hydrogen in the power station, where the gas has no oxidant mixed with it, and has to wait until it gets to the air around it........ Hydrogen mixtures with oxidant have exceptionally low energy requirements to ignite, in the range of only milli joules.... so any kind of even "so fine you cant see them " static sparks can cause total detonation.....it does not need to be contained to detonate, same with acetylene... they burn so fast that any mixture of gas and oxidant will explode rather than burn.... hence the bang you hear igniting the acetylene in the gas torch. ( yes still technically burning......., but more like an explosion than a rapid burn )...

Those cells exploded... either poor leads, internal break, or static spark.... but that was an explosion. I've been too close to too many of them to not recognise it when I see it. It is fortunate that the explosion did not spread to the whole lot. I have not seen that happen, usually only a few at a time.

edit:
 Although energy to ignite is in the tenths of a millijoule range, the temp required is quite high comparatively. (>1000F)... so red ( dull not bright) hot wires may not cause ignition, but the melted plastic..... should it actually ignite and burn and / cause a plasma ( flame) of any kind.... then away she goes.


My 675AH battery box
It has 24 T105RE batteries in three strings. Separate leads of all the same length to each string with 100amp enclosed fuses inside the shed for each string (48v).

It is big on ventilation, and isolation from other flame sources.... never again I hope.
ila_rendered

ila_rendered


................oztules

Edit fixed up typing fault in AH figures... not 750ah... thats the 100 hr rate
Flinders Island...... Australia

Offline Wolvenar

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Re: Exploding lead acid battery explosion
« Reply #17 on: April 14, 2015, 11:51:41 PM »
I've had similar experience, this is one I happened to be near, and able to document the aftermath.

Not the same as a larger or multiple detonation, but none the less it did not feel good.

http://www.anotherpower.com/board/index.php/topic,53.0.html
Trying to make power from alternative energy any which way I can.
Just to abuse what I make. (and run this site)

Offline oztules

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Re: Exploding lead acid battery explosion
« Reply #18 on: April 15, 2015, 01:28:31 AM »
Gotta love that label too Wolv.... 8)

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

Offline off the wall

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Re: Exploding lead acid battery explosion
« Reply #19 on: April 15, 2015, 03:49:42 AM »
OUCH! Thanks - it's good to see others have experiences. My worry - and that of the family and helpers - is that the source of detonation in the cells we experienced was internal. Connexions were tight and there were no external ignition sources.

The solution that you're all appearing to be suggesting is . . . to keep batteries in a well ventilated bunker . . .

This thread is important because as more people get into the idea of solar power and battery storage, people are entering a realm in which they're unfamiliar with what they're getting into.

Personally my system, against all conventional advice, uses SLA batteries ejected from emergency power supplies and this has enabled me to put together a large system economically and so-far successfully. As a matter of interest, a useful material for bus bars is 3x25mm lightning "tape" and, again, I colour code this keeping copper for positive and alumiunium for negative, and doubled up where appropriate for current carrying capacity. All my connectors are similarly coded with brass for positive and zinc plate for negative. Using 12V SLA batteries in multiples for 24V and obeying the requirements for only gentle exercise on each battery, instead of conventional hefty connectors I use a piece of solder wire which melts at 7 amps. In this way there is current limitation at the source of each point of power. Because of cheap availability, I use 6mm red and black solar cable to connect groups of 10 or 12 batteries to a local connexion taking 5 or so such groups of batteries and each of these fused with a dozen strands of solder wire twisted together. From these groups two parallel 6mm cables (ensuring equal length cables throughout the system as far as possible) take the group connexion back to the bus bar and 9 or so such groups all switched add to the current carrying capacity of over 100mm cable. LED voltmeters at the group connexions show the voltage at each such junction and any differences between them, and the difference between those voltages and the voltage at the bus bars indicate any poor connexion issues and any high currents. This distributed system has the advantage that sharing among 9 or so groups of batteries there are no high currents in any individual places other than the bus bars to the inverter - and likewise minimising any risk of spark as in the case of a poor contact, there will always be an easier current source from the 8 other groups rather than a spark or dangerous current through a high contact resistance.

This system is unconventional but I believe avoids the safety issues leading to the photographs above.

Best wishes

OTW

Offline rossw

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Re: Exploding lead acid battery explosion
« Reply #20 on: April 15, 2015, 05:42:41 AM »
The solution that you're all appearing to be suggesting is . . .

.... to not use lead-acid!

Quote
This thread is important because as more people get into the idea of solar power and battery storage, people are entering a realm in which they're unfamiliar with what they're getting into.

All the more reason to encourage the use of "safer" technology. AGM (fairly safe, but not very forgiving), perhaps LFP.

Quote
Personally my system, against all conventional advice, uses SLA batteries ejected from emergency power supplies and this has enabled me to put together a large system economically and so-far successfully. As a matter of interest, a useful material for bus bars is 3x25mm lightning "tape"

I used copper busbar, cut to lengths and drilled.  I think most of mine was 25x5mm and for the end bars I used 36x5
 (from memory)
[/quote]

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alumiunium

I would STRONGLY advise against the use of aluminium in ANYTHING around your batteries. It's a disaster.

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instead of conventional hefty connectors I use a piece of solder wire which melts at 7 amps.

7 amps?   On a 24 volt system?  Thats so near useless as makes no difference. I pull peaks of near 150A PER BANK at 48V
And charging a system at a maximum of 7A? That'd be fine for pocket-sized cells, but it is chronic undercharge for anything in the 200+AH range.

Quote
This system is unconventional but I believe avoids the safety issues leading to the photographs above.

Please don't take this the wrong way... but most of what you've put forward is so far removed from any practical application as renders it either useless, or ok for some esoteric system with a peak demand of around 100 watts, and not much more than that in PV to charge it.

My system is NOT a showpiece, it's NOT best-practice, and it's NOT all new gear. It does run my home, 2 offices and workshop, and has done so for a decade with no problems. It's second-hand AGM (sealed lead-acid) cells, running around 1000AH capacity (faceplate would say 1500AH @ 48V).


Offline off the wall

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Re: Exploding lead acid battery explosion
« Reply #21 on: April 15, 2015, 06:38:54 AM »
That's a nice system

But my mention of aluminium is for intergroup bus to the inverter and solar controllers and nowhere near batteries.

When one is using multiples of 38 to 60 or 70ah batteries, limiting draw and charge to C10 or C5 at most, and therefore fusable wire at 7 amps per battery, is not inappropriate. The concept makes a lot of things non-critical which could be otherwise.

Best wishes

OTW

Offline rossw

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Re: Exploding lead acid battery explosion
« Reply #22 on: April 15, 2015, 03:33:52 PM »
That's a nice system

But my mention of aluminium is for intergroup bus to the inverter and solar controllers and nowhere near batteries.

Given the problems I had of connections constantly coming loose, high contact resistance etc, I'd never, ever, use aluminium again in this application.

Quote
When one is using multiples of 38 to 60 or 70ah batteries, limiting draw and charge to C10 or C5 at most, and therefore fusable wire at 7 amps per battery, is not inappropriate.

I hadn't realised you were using such small cells, but I would still contend that "fusible wire" is a bad choice. Should you have a fault (which may cause significant gassing), then a fusible wire/link may well prove to be just the ignition source you DON'T want around!  Far far safer to use HRC fuses, keep the arc fully contained and rapidly quenched.

Offline off the wall

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Re: Exploding lead acid battery explosion
« Reply #23 on: April 15, 2015, 05:14:21 PM »
Yes - thanks - it should be pointed out that my personal system is a world away from the traction wet cell explosion experiences the subject of this thread. The busbars I'm describing are nowhere near the battery end of things and the aluminium works well in the context chosen as well as providing visual identification of the negative rail.

Because I'm using SLA batteries offgassing is neither allowed nor happens. On the solar controllers I set the maximum charging voltage to 28.8V in cloudy weather to take advantage of any available peaks of sun and 27.6V in continuous sun. Any risk is an accidental short and the interbattery fusing provides the best failsafe protection in the context.

The cells which exploded were not being operated as part of this system and the matter of concern is what internal source of combustion can have caused ignition.

Best wishes

OTW