Battery bang

Submitted: Friday, Aug 22, 2003 at 06:56
ThreadID: 120086 Views:2051 Replies:6 FollowUps:0
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Re the exploding battery I mentioned last week.

The owner (a maker of high quality 'RVs) would prefer not to be identified. I spoke to him a few days ago and the facts are these: (it happened to his own vehicle).

The battery was in an internal but what had previously assumed to be an adequately ventilated enclosure - with an open steel mesh base. It was being charged by a typical mid-quality non-smart charger that has no 'float' mode, but had previously boiled batteries dry.

The vehicle in question has a front-located slide-out kitchen that is electrically actuated. When the owner pressed the actuating button, the battery exploded - fortunately blowing the steel mesh and the remains of the battery downwards. It is unclear whether the sudden load imposed by the slide out electrics perhaps caused a poorly connected battery cable to overheat and arc - or what. There was no electrical switching mechanism inside the battery enclosure.

He says it was 'one hell of a bang' - and would have been a great deal worse had it not been for that open mesh base plate.
Collyn Rivers
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Reply By: Deleted User - Friday, Aug 22, 2003 at 06:58

Friday, Aug 22, 2003 at 06:58
Weird !!! Was the battery being charged at the time ? You would assume it was to supply enough explosive vapour to blow through mesh floor ..... especially with a reasonable amount of venting ??? Another assumption is that the vapour was leaking to around non flameproof kitchen motor and armature arcing was ignition source ..... highly unlikely but not impossible. All motors unless flameproofed are sources of ignition. Collyn has said that a cell shorting can be source of ignition, or loose terminals, probably never know ? By the look of it a battery can supply two parts of the fire/explosion triangle which only leaves ignition source to complete it .......... one part of the triangle is cause for safe handling .... two parts are downright dangerous ...... As most people know the fire/explosion triangle (equation) is made up of ...... FUEL + OXYGEN + IGNITION = FIRE/explosion If one thing comes to light through all this it is ......... the batteries are an ongoing maintenance item. They are NOT set and forget ... check terminals for tightness, check electrolyte levels, use a quality charger and dont overdischarge. Keep sources of ignition away from battery compartments. Anthony
AnswerID: 559462

Reply By: Deleted User - Friday, Aug 22, 2003 at 06:59

Friday, Aug 22, 2003 at 06:59
With flammable gasses there is a critcal gas to air (oxygen) ratio whcih significantly increases the explosive nature of the gas. If there is too much or too little air the severity of the explosion is very much reduced. It doesnt take a large volume of flammable gas to produce a large explosion if the gas air mixture is right. Having a static ventilator ie non forced ventilator can actually contribute to the explosion. Fan forced ventilation is better. Vidas
AnswerID: 559463

Reply By: Deleted User - Friday, Aug 22, 2003 at 07:00

Friday, Aug 22, 2003 at 07:00
It is unlikely and bothering that the cause of the explosion may not be discoverable. The battery was totally wrecked - the sides were blown out of it.

My guess and it's only a guess is that it had something to do with thermal run-away. A seriously overcharged battery heats up, enhancing its ability to accept a charge - which heats it yet further etc.................

This generates a great deal of hydrogen and. as Vidas points out, once passed a critical concentration (10%) it goes off with a serious bang if ignited.

What is unclear in this scenarion is whether or not the action of operating the slideout (a) was a coincidence; (b) caued a spark from the switch contacts that somehow ignited the gas; (c) -- any my guess - the heavy current drawn by the slideout motor possibly caused a slight arc across a poorly made or corroded battery terminal or cable.

What we do know however is that the battery charger was one of those only too common heavy current and negligible automatic-control types. If that had not been there and operating it is unlikely this explosion would have occurred.
Collyn Rivers
AnswerID: 559464

Reply By: gottabjoaken - Friday, Aug 22, 2003 at 07:01

Friday, Aug 22, 2003 at 07:01
And don't forget that the hydrogen generated is lighter than air, so a mesh base will not stop a collection of gas under the cover. Ideal explosion situation - ready supply of oxygen and a bubble of hydrogen.

You tend to put "gas" in the same category as propane where a mesh bottom will let it drain away!

Ken
AnswerID: 559465

Reply By: Deleted User - Friday, Aug 22, 2003 at 07:02

Friday, Aug 22, 2003 at 07:02
This message has been deleted by the author.
AnswerID: 559466

Reply By: Deleted User - Friday, Aug 22, 2003 at 07:03

Friday, Aug 22, 2003 at 07:03
Ken
You do not appear to have read the early postings when this first arose. My article posted in the documents section of this site makes it totally clear that hydrogen gas is lighter than air and thus rises.

The reference to it being fortunate that the base was mesh would I think have been understood my most readers in the context that it dissipated the force of what was a considerable explosion and directed it downward rather than into the van.

The article also emphasises that under some conditions the gas may not rise - it can bbe trapped and pushed back down into the enclosure by wind and thermal effects.

Contrary to earlier reports, that the enclosure had no other electrical devices within it, photographs of the wrecked enclosure show that thee was what appears to be a battery charger and possibly a switching solenoid.
Collyn Rivers
AnswerID: 559467

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