Old car batteries - A warning :(

[Al]

I've been adding to my colection of deep cycle batteries and inverters recently, and now have plenty of capacity in the event of (all to frequent) mains failure.

While rearranging the garage, I found a couple of old high AH car batteries that had sat unused for many years. With a view to getting a bit of 'free' capacity to use for short term use as lighting in the garage, I thought I'd have a go and get them charged and cycled.

So, using my 'smart' charger, I started work on one. After several normal charging attempts and a couple of reconditioning cycles the charger was still reporting the battery as faulty. At this point, I should have given up. But ...

I thought I'd give the battery one last try on a slow charge. That was a mistake.

Sitting indoors yesterday evening, we heard/felt an explosion. I suddenly got that terrible feeling ...

Opened up the garage - Full of acrid fumes and bits of battery casing. Having opened up the doors at both ends, donned double layer rubber gloves and old clothing I went to examine the wreckage. The battery had exploded, leaving debris in a 10 foot radius. There were even bits in the rafters :( More worryingly the car in the garage had been splatted with acid.

Neutralised the pool of acid with baking soda and dumped the carcase of the battery in a large ploycarb bucket. Washed the car down in the drive (8:30pm - The neighbours must have thought I was mad!) and it looks like there's no damage.

Could have been worse - I might have been standing next to it when it blew. All I have to deal with now is a bucket full of broken battery and acid. I'll probably just fill it with cement rather than use a ton of bicarb. Oh, I decided not to use sodium hydroxide to neutralise it - The hydrogen released might have caused another explosion :)

So, be warned - Old car batteries are not worth the risk in 'rescuing'. Lesson learned.

Al.

[Invisible Man]

Anything that might cause gassing is better done in the open air. Remember one case where contacts were accidentally shorted (dropped spanner?) after a fast charge. Person ended up with part of their specs frame blown into his eye and was blinded in that eye. Batteries are one of the things I have learned to give a bit of respect to after 25 years handling claims.

[Andrew Mawson]

inverters

charger was

rubber gloves

carcase of the

looks like

hydrogen

'rescuing'.

respect

Yes - I foolishly took a battery off charge in my cellar a few years back by removing one croc clip (rather than switching off the mains). The resultant spark ignited the hydrogen in one cell which blew my glasses off and put acid in my eyes. Fortunately other than the ruined battery there was no more damage than a broken pair of glasses anda bit of smarting.

AWEM

[Jules]

Interesting tale - in what sense is the charger "smart"? Do you think it was the reason for the failure because it misread the battery status and tried to do something clever (i.e. a traditional slow/fast "braindead" charger might have worked)?

Last time I had a battery that hadn't been used in a very long time it took several days on slow charge (using a dumb charger) before it came back to life. It was never 100% (i.e. seemed to lack the kick that it once had), but would at least hold a charge.

(truck battery's sitting out in the garage at the mo after some overcharging drama with half its fluids boiled away - I'm not sure whether to even try and bring that one back, or to just cut my losses and buy a new one!)

cheers

Jules

[Harry Bloomfield]

Andrew Mawson used his keyboard to write :

I make a habit of wafting some air around a battery to disperse the hydrogen. Even if you turn things off it is no guarantee that no spark will occur.

[Dave Plowman (News)]

The lesson should be that batteries should not be charged in an area with poor ventilation. And sparks. Or fast charged with the cell filler plugs in place.

[Onetap]

Did you check the level of electrolyte in the cells?

I blew one up 20+ years ago, I had left a big spanner on the conveniently flat top of the battery before turning the engine over. The vibration on turning the engine over moved the spanner which shorted out the contacts and there was an explosion like a grenade. I found the spanner twenty or thirty feet up the road. All that remained of the battery was the bottom 2 or 3 inches of the casing containing a pool of steaming electrolyte. Fortunately no one was passing-by and I had the raised bonnet and windscreen protecting me from the shower of plastic shrapnel and hot acid. I think the low electrolyte level had allowed space in the cells which filled with H2/02 mixture and the spark ignited it.

Lesson learned. Note that the bit in the Haynes manual about jump- starting cars ( that bit that blokes never read because they think they know how to jump start a car) recommends the final connection should be made to the earthed metal work, far away from the duff battery; the connection is liable to make a spark.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Al saying something like:

Bollocks. You just didn't know how to do it, safely.

[Dave Plowman (News)]

If a battery is so flat it required a jump start it won't have been gassing. ;-)

[Al]

It's one of those multi-phase ones - Constant current, constant voltage, then constant current again. Except this one also has slow start, battery test on completion, then final topup. And a manual reconditoning mode (basically chopped DC to help desulphation). It works fine with other batteries (of the non-dead variety).

No. The charger display showed the actual current and voltages correctly. The battery was dead. It's ever deader now! ;-)

Al.

[Al]

Hmmm. It was well ventilated, there were no sparks, and it was a slow charge. Didn't remove the caps as it was a vented battery. Rather more vented now than it was before ;-)

The explosion was internal to the battery, not external.

I have another old battery. I think that one can go straight to the recyling at the local tip. I've had enough excitement this week.

Al.

[Al]

Probably not.

Is there a magic method for resurrecting 5 year old dead batteries? Bear in mind that this was a slow charge on a vented battery in a well ventilated space and that the expolsion was internal rather than external.

My point was that a dead battery is just that. Dead. Although as you have heard it is possible to make it even deader :)

Al.

[george (dicegeorge)]

i believe that once a lead acid car battery has been left flat for more than 3 days it is dead. The plates buckle, or something like that.

I test them by putting a multimeter across it, then connecting an oldstyle car headlight, 60 watts.

If the voltage drops from about 12 volts to less than eleven, (often ten and a half) then i deduce that one of the 1 1/2 volt cells is knackered, and i throw away the battery.

The local car scrappy pays £1 for a car battery and charges £15.

At the recycling center when they're not looking I swap my dead ones for ones with a juicy voltage on my multimeter!

that's in the spirit of the law, if not in the letter of it,

[g]

Al wrote:

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Al saying something like:

I've resurrected several, but not as old as five years, so all bets are off. ( Actually, I do have an ancient one of of the Landie diesel that hasn't seen a charger for at lest five years, to I'm now tempted to give it a go. )I use a very low charge current - about half an amp, for a week or two until an ordinary 'traditional' charger with ammeter will come off its stop. A useful regulating resistor is the remaining good filament of a headlamp bulb - the one you didn't want to chuck out as it might be useful for something. Anywaye, after up to a fortnight of this, the cells are starting to take a charge again and it's worthwhile trying the unregulated charger on it. Once you get it to approach something, anything near its capacity, now is the time to do the EDTA treatment on it.

YOu drain it and flush it and put new electrolyte in, with some EDTA.

Then give it another ordinary charge. If you're lucky, the battery might last another year or two.

[dennis]

There are only two ways to explode the battery that I know of.. hydrogen and an ignition source.. hydrogen and blocked vents.

[Andrew Gabriel]

Boiling electrolyte and steam? Don't know if that's realistically possible on charging (certainly is on discharging/shorting).

[dennis]

That probably makes three. ;-)