Hi,

Can a sealed lead calcium 12 volt 7 amp battery explode or at least catch fire? I'm charging one at 600 mah as recommened and I think it started making a very subtle crackling sound.

Thanks

I've never had one explode or catch fire.

Yes, if charged at to high a rate or if a sudden short circuit accross the terminal with a cross sectional area sufficient to not burn through quickly occured. Anything that will allow the release of the stored energy in a very short period of time could be explosive.

Thanks Rodney,

The reason I asked is because the battery got low at the field and I put it on the charger with is a Hangar 9 600 mah charger designed for the task. It was only on for about 4.5 hours and I noticed a really really subtle occasional crackling sound. Is that a bad thing?

If I listen to my 12 volt battery as it charges, I notice the exact same thing. A VERY subtle crackling sound, almost like food sizzling on a frying pan. I would have never noticed this unless I looked for it. I assume its normal. I'm charging at 250 mAH

My unsealed Pb 12V 4.5Ah batteries would also do this - plus I could see the electrolyte bubbling. I was using a 2/6 amp car battery charger and determined this was far too high of a rate.

I now maintain all my Pb batteries via one of those Deltran Battery Tenders. Simply plug it in and forget it until it's time to fly.

Yeah the crackling sound is normal. I use a normal 12V motorcycle battery and a 6 amp car battery charger and get the same sounds. I think it might just be the acid bubbling.

Thanks guys for the responses. I've heard about that battery tender, I think I'm going to check that out.

It shouldn't explode unless it's being charged at a ridiculous rate or has a dead short.

600mAh shouldn't hurt it at all. Are you charging in "SLA" or lead acid mode, if not that could be a problem.

I had crackling on my field box, and couldn't get much power out of it. Turned out to be an oxidised connection rather than a battery problem.

You will know if it explodes, believe me! You would be buying a new flight box.

Over drawn or over charged sealed batteries also tend to "inflate" first.

The gas produce causes the plastic casing to inflate like a puffer fish.

When you see a small amount of this, it's time to replace the battery.

Good advice!

I'm trying to revive some near new SLA's that I recovered from a toasted UPS at work. The batteries appear to have taken a hit during the UPS failure so I'm being very cautious in trying to charge them. If I see the slightest swelling they will immediately go to the recycler. With luck, they may just need a good cycle or two (hoping anyway).

You can often obtain OEM UPS batteries for good prices and use them in your field box.

That's what I did. I'm running 21Ah batteries in my box.

They charge slowly, but you don't have to do it very often... heh.

600 ma is just over 1/2 amp which is an acceptable charge rate for the battery. That charge rate isn't going to "blow up" the battery however unless something bad has happened to the battery or it has been ignored for too long it will never be completly dead so I would guess that all you really need is 2 to 2 1/2 hours charge. [8D]