C.P.R. for batteries

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alanporter

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A motor mechanic has just told me that, to revive a lead acid battery that is failing to hold a charge for long, is to flatten it completely, by connecting to a high amp draw, such as a car headlamp, leaving it connected overnight, then to short out the positive and negative terminals, using suitable precautions (whatever they are). I could not understand from his explanation what this actually does. Is there an electrical wizard out there who can comment ? Thanks.
 
At a guess, the idea is to generate enough heat (by shorting) to cause some of the sulphate to drop off the plates and clean them up. This sounds v.dodgy though.

The instruction to run the battery down first is probably to stop you actually melting whatever is doing the short (cables, spanner) and burning or blowing yourself up on the spot.

Suitable precautions probably include standing behind a riot shield at 50paces wearing safety goggles and a hard hat, and sending the motor mechanic to try this first and see what happens.

dv.
 
Your mechanic friend?? must want to give you a big fright! Shorting out a car/boat battery can lead to big sparks and injury, or if the shorting wire is small guage it will just blow like a fuse. I'd say don't try it.

If you have followed the Volvo Ocean race I believe one of them had a fire on board when something dropped onto the battery and shorted it.

I know the mechanic said the battery should be flat but you need to be very sure before shorting any source of current./
Ray
 
An old trick actually. Don't short it when it has any real charge in it of course as you will wreck it, or worse but if you put a high drain on it to "empty" it first the last connection across the plates is supposed to stir up the sediment that falls to the bottom of the plates. Really this should only be a precursor to emptying and flushing the battery and re-charging with electrolyte of the correct SG (not just distilled water). Not really worth doing these days though as its only going to perk it up a bit, not revive it to new condition and a new one is not that expensive in real terms.
 
Oh! do be careful - don't go shorting out batteries - if of any size you'll risk a fire or burnt hands at least.

I've partially revived a number of batts by very slow charging (over days) using a very small charger (not automatic type) & allowing the voltage to reach 14.5V+ for at least 12hrs. By slow, I mean a charging current of 2A or less at the start & don't worry if initial charge rate much much less; be patient & allow 24hrs before deciding. It's not worth buying a tiddly charger just to do it - but if you already own one - well worth a go, but not if said battery is your sole starting batt. on a boat.

Please don't put spanners or cables across battery terminals .
 
Re: C.P.R. for batteries .... there used to be a fluid ...

You could buy Battery Reviver ... a small can of fluid that you dropped few cc's in each cell to revive them - I believe it acted on the sulphate coating that builds up on plates ...

Haven't seen it around for years .... mate of mine used to sell cars with duff batterys ... he used it to give enough life to the battery to sell the car !! Rotten swine ..........
 
Re: C.P.R. for batteries .... there used to be a fluid ...

Another 'trick' I learnt in the early 70s was that some car battery manufacturers made cases and plates to exact specifications. After a few visits the rep became friendly, and when quizzed on why batteries always seemed to die, a few weeks after the garantee had run out, told us, they were made so the space in the bottom filled up and shorted out.

We had just such a battery, and it was manufactured so the top could be cut out, like a lid. We cut this off, emptied it out, and sure enough the battery worked as new. Forget exactly how we stuck it back on, probably with bitumin (underseal) or something. However I know I used this battery on a buggy type thing we had built, and it was still ok months later. As this oversize 'go-cart' was just for riding round the orchard at the back, it did not of course have any charging facility, but despite frequent use, the battery seemed to last a few weeks.

When my car dynamo (yes they were still used on my old cars, alternators were only on new ones) packed up, I used to struggle home using only side lights, or less. So it must have been lights that ran the battery down, far more than the heavy starting current, which is usually only for a few seconds.
 
Years ago in labs ...

It used to be possible to buy wet-cells that you could take apart .... literally a lift-off top with plates / terminals etc. in place. The container could then be cleaned and refilled with new electrolyte. The plates and terminals could be washed / lightly wiped before returning to the container ....

They looked like large motor-cycle style batterys with the clear bodies .. so that you could see the state of the inside etc.

As a standard wet-cell they were as a car battery nominal 1.5V .... charged up to just over 2V .... they could be series or parrellel as required to increase power or voltage.
 
I hate to argue for the sake of it Andy and I am not, but others should know that in fact the reverse is true. A deeply discharged (truly flat) battery will never hold a charge if you try trickle charging it. It needs a "boost" at a high charge rate to get it going first. I have no doubt that your trickle charger did a good job of reviving a battery run down on the car or boat. One of the problems with simple generators is they never really get the battery to a high state of charge. That's what "smart charging" is all about. It's also why they make trickle chargers. If you ever find a battery won't charge at all though take it down to your garage and get them to put it on boost at about 30 amps after that it will accept a trickle charge again.
 
Re: C.P.R. for batteries .. cheap battery\'s

They might be for average common sizes ... but my Suzuki Vitara ... UGH !! For such a tiddly little battery was 50% more than the girt big HD job I fitted to the boat couple year back.

I will now only buy from Breakers yards ... as the Suzi battery lasted approx. guarantee period ... (seems Ships Woofy and I have same problem - different vehicle !). My brother picked up a Breakers Yard job for a fiver and that has lasted just the same - in fact is still going strong ....

You also have to be careful about useage and clauses in the Guarantees ... Ships Woofy found that out ... use as Starting Battery seriously reduced the Guarantee period ....

You may find that the use you put it to is outside the Guarantee coverage ....
 
Try EDTA+
http://www.pureresearch.co.uk/

I have used this on old batteries that have been down to 11.5 volts, within days back to 12.5 and 13 with in weeks, lasted years.

This is a heavy metal
It cleans the sulphate from the battery plates during charge and then during discharge the sulphate goes back into the acid.

Carries on working.

Not sure about gel type ?


This is a more gentle way of removing the sulphate coating on the lead plates and keeps working.
 
that's the theory Mike - but having made several dead batteries (that took almost no measurable charge, even on a big charger at a higher voltage for some hours& wouldn't even light a bulb properly) work again - I'll trust my experience .
 
Many years ago, I had a car battery explode (caused by sparks, I was testing a 12 v motor) and it did just that! There were just small pieces of casing and plates left and acid everywhere. Luckily for me, the acid went straight up and missed my face, but my clothes soon disintegrated! Pieces of the casing hit and broke the flourescent lights above, showering me with glass fragments. I was completely unhurt, but I know that I will never be that lucky again and have great respect for batteries. Never connect a wire with a load on it to a battery as it will spark, make sure the circuit is switched off first.
Peter
 
Re: Years ago in labs ...

Hey!,

Do you remember Leclanche cells in square glass bottles about 5in square by 7in high..........with a 'pocket' at the side for the zinc rod?

How I wish I'd salvaged some from the tip beside the coal mine......jars would be worth a fortune.

Vic
 
Re: C.P.R. for batteries .... there used to be a fluid ...

Yep, was common practice to literally flush batteries out with a hose to shift the crud from the bottom; rinse will distilled, refill with new sulphuric. These days would cost more that a new battery!!.
 
Re: C.P.R. for batteries .... there used to be a fluid ...

Instead of a dead short, would a relatively low resistance (like a load tester) be any better / safer?
 
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