First Aid for Dead Lead Acid Batteries?

[bulgin]

Hi

I have 'accumulated' a couple of 12V dead lead acid batteries from rechargeable lanterns and from a UPS. They are rated from 1.3a/h to 7a/h.

One of these had a corroded off negative terminal which I succesfully repaired today by chipping out the surrounding epoxy and re-attaching a similar terminal by selftapper and re-filling with epoxy again.

I took the top plates off and removed the rubber caps on each cell of three of these batteries and found them completely dry and the cells sulphated, if that's the correct terminology.

I filled all the cells with distilled water, replaced the cell caps and put them on slow charge with a charger which I bought for one of these batteries.

I realise a full charge may take several days on each and since I haven't used the charger for several years, I checked its output which is 11.7V @a/h?

Before these procedures, I checked the capacity of each battery and got dc readings of 5.7V, 7.7V etc which was insufficient to light a 12V bulb or even a 4.5 or 6V lightbulb.

After several hours on charge, the capacity has increased to around 9.5V with still no capability to power any dc lightbulb.

Before I dispose of these batteries, is there any method with which to resuscitate them for further use? Long ago, some auto accessory stores used to sell a concoction which they claimed, could be used to revive this type of battery. As far as I know, none of these batteries have shorted-out cells but how can I test for this condition?

Thanks for your advice and attention.

bulgin

[mwmkravchenko]

Hi bulgin!

You may start with the charger. If it is really giving you the 11.7 volts you show it is your first problem. A 12 volt battery usually charges at 13.5 volts dc.

There are de-sulphating circuits that I have collected if you are interested. Just drop me a line and I'd be happy to send you a copy if your game on making one up.

Mark

[bulgin]

Hi Mark

Thanks for your attention. You're right. I checked the output of the built-in chargers of two lanterns from which two of these small batteries came and it shows 13.5V on both. The small charger I'm using now (which has had little effect) was bought years ago as a charger for one of these batteries. I never checked its output or charging rate as I assumed the counter salesman knew what he was selling me - often a very wrong assumption!

I also have a car battery charger for 6V or 12V car batteries rated @ 4A which I have used for years successfully but thought this equipment would not be suitable due to the small size of the batteries I want to re-charge now.

Then, I have a bench powersupply with digital volt and amp display where I can set what's needed accurately. I think this equipment is rated @30V 5ampere. Will this equipment be suitable to use?

I would be interested in your de-sulphating method as it seems a waste to dump these batteries.

Thank you for your kind assistance.

bulgin

[Paradise_Ice]

I was told once that by using an Arc Welder to short the terminals for a few seconds of a lead acid battery it can refresh it, something to do with removing the crystals from the lead plates? This sound dangerous to me so I don't recommend it, I only mention it as it was interesting and maybe somebody can dispel or verify this..

I have no idea if this is true or works, do some research and see what you can come up with.

[Ron E]

I don't know about South Africa, but in the USA lead has a scrap value.

I'd just buy new cells. You can usually get them fairly inexpensively.

[scott wurcer]

Do a web search for high frequency pulse restoration of lead acid batteries. I have heard some off-grid folks have had good success.

Ron - current avatar is pure coincidence

[bulgin]

Hi

Thanks for your kind replies. I did some searches and came across both the arc welder thing and various circuits for pulse re-generation but the former has unacceptable risk and I'm not convinced about the latter. The charger I've been using has a pot so I adjusted the output to 13.5V but this still didn't help as these batteries are beyond salvage. Yes, lead is recyclable here too. Heck, they even saw off lamppoles in my neck o' the woods

On my next trip to where the scrapdealers are, I'll just take the dead ones along.

bulgin

[Renron]

Try this link,
I tried this method but it didn't work on my WAY past dead batteries. But Epsoms salts work on recharging a lead acid battery.

http://www.ysuusy.com/YSUUSY_BATT1.html

Ron

[Steerpike]

I looked into this a while back, and had no great success.

If it battery gets one weak cell, the battery as a whole just won't deliver any subtantial current anymore, and to recharge only one cell is impossible in MOST batteries.

Shorting the battery is likely to damage it further - as the high current heats up the plates, causing them to warp and shed the porous lead sulphate that makes up the electrode.

Battery acid is a key constituent in local illegaly brewed "beer", so there's a market for this stuff!

[scott wurcer]

Originally posted by Steerpike
I looked into this a while back, and had no great success.

If it battery gets one weak cell, the battery as a whole just won't deliver any subtantial current anymore, and to recharge only one cell is impossible in MOST batteries.

Shorting the battery is likely to damage it further - as the high current heats up the plates, causing them to warp and shed the porous lead sulphate that makes up the electrode.

Battery acid is a key constituent in local illegaly brewed "beer", so there's a market for this stuff!

I think the stuff is pretty cheap on its own, There has to be lead taint comming out of a battery.

BTW automotive batteries are designed to have too little structure on the plates when totally discharged anyway. Solar off-grid batteries (golf cart, phone closet) are designed with plate material left after deep discharge, more expensive too.