Old Husband's tale

My suspicion is that when a battery is set down, it sits there a long time. Long enough, and undisturbed enough, and uncharged enough that it accumulates a layer of dust and dirt, which in conjunction with moisture, slowly conducts off to the concrete floor or ground. And while a concrete floor, or dry dirt for that matter, isn't as much off a conductor as steel, it most certainly will conduct - I got nailed as a kid standing barefoot on a basement floor! So putting the battery on a 2x4 or plywood or something provides a better insulator and maybe even a better break in the dirt path..

Just my thoughts.

WT

Urban myth. Google on urban myth battery concrete.

Hi...

Oh oh, here we go :)

I believe it either is or was true.

I hold that the damage was caused by interaction between the very alkaline cement and the battery acid.

Take care.

Ken

How does the acid get there? The case is acid proof, otherwise the steel it sits on in the car would corrode through in even shorter time.

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    Dave Plowman        dave@davenoise.co.uk           London SW
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I set them on the ground all the time and never noticed a problem.

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1. Urban myth

1. Alkaline cement/battery acid

2. Dust dirt and moisture

1. Basement floor

CJT said he never had a problem, but didn't mention anything about time. How long ? Nobody ever said it was dead in minutes, or even hours.

A buddy and I have been discussing this, after reading the responses and I can no longer summarily dismiss the effect, if the "urban legend" is indeed true. At this stage I must admit that there is a possibility.

1. A reaction between whatever solubles are in or on the cement, along with the highly acidic content of the battery housing, which has some porosity, is an interesting possibility.

All of this might be enhanced in more humid climates. Even on cement, even if it doesn't rain, if left long enough metals will corrode or rust on the bottom.

3.Basement floor : While copper is an excellent conductor, cement is not. That is not to say it is a good insulator. Your legs act as wires, not very good wires, but functional enough to kill. If you are barefoot on cement, it's not making all that good of a wire either, but look at your footprint and you see the cross-sectional of this wire. A bit bigger than the wires in your basic 12-2 Romex you think ? A copper conductor of that size could carry thousands of amps. It needs alot less to burn you, or to discharge your puny battery over time.The linear resistance of a piece of wire is inversely proportional to it's cross sectional area. So what do we have here, how many ohms ?

Actually I would be at a disadvantage here with my 13 wide sized feet.

When I want to know if something is true I need to prove it to myself. Thanks all so far. I play Devil's advocate against my own initial point of view for that reason. All these factors are evidence that this myth might be true, but initially came from personal obsevations. Cause was attributed to effect, but the matter was not looked into further.

JURB

Further on:

1. Alkaline cement/battery acid

Most good scientists know that everything dissolves into everything, it just a matter of how fast. As some minute conductance developes through the bottom of the battery, if we are to assume this theory fact for the moment, means we must accept the possibility the earth and/or concrete which has a solid Earth ground throughout may indeed have an effect that was unforseen.

It it also unreasonable to expect that there is no seepage at all in the life of these batteries. If some electrolyte soaks into the dirt, even an infinitesimal amount could it possibly be setting up cells polaraized opposing those in the battery ? This enhances whatever conduction there already is. Yet if the battery is removed you might still not see a voltage on it, because the bottom of the battery forms one of the plates of this self made battery under itself. (I think you know what I mean)

I'm not saying this is true, but it is possible.

JURB

Hi...

First - the story never ever called for hours, or minutes. Being perhaps the "old guy", I believe it came from those "olden" days when cars were put aside for the winter. (at least here in Winnipeg (Winterpeg) Canada, where we get more than our share of -40 degree days.

Folks would drain fluids, remove tires and put the car up on blocks, and bring the battery inside to store in the basement. So we were talking 4 or 6 month periods.

Second - in support of my position, I invite an experiment from any who are willing and in a position to do it.

Those of us who change our own batteries pay a 5 dollar deposit when we buy a new one, refundable whenever we return the dud. I suspect not many would suffer much were they to do without that 5 bucks for a month or two.

So, anyone buying a new one, with a still usuable but due for replacement, keep the old one. Put it somewhere safe on the newest cement available. Keep the kids safe, put it perhaps on a garage floor.

Leave it alone for a month or two, then take a good look at it. The case _will_ be covered with salts.

I fail kindergarten level chemistry, but what are those salts? Where did they come from, and what effect does their loss have on the battery?

Let us know; then take the battery back for your 5 bucks :)

Take care.

Ken

I'm with you; I think this is a complete myth. The conductor theory completely ignores the fact that they sit on steel while in the cars, and the concrete dust theory ignores the fact that putting it on a little square of plywood doesn't change the amount of concrete dust in the air around it.

My personal theory is that this "problem" just shows up when a battery is taken out of service and stored in a corner for a long time. Since any battery will slowly self-discharge at some slow rate, the time alone is usually enough to explain the fact that the battery is later found to be dead. Add this to the fact that such batteries are often already old and possibly from cars in poor condition (poor charging voltage?) then the prognosis just gets worse.

Any lead acid battery left discharged for long will become sulfated. This can be easily reversed, but not quickly; it takes time, and most people won't spend the time. It can take a week or more, but by then most people have declared it dead and replaced it.

There's also the explanation that the battery dies because the concrete is cold, thus maintaining a temp gradient across the electrolyte. Proof of this is claimed to come from the fact that diesel-electric submarine batteries had active stirrers to keep the electrolyte at an even temp. I won't claim to know anything about submarines, but I suspect that stirring would be a very good thing to keep the electrolyte concentration constant. Otherwise, the electrolyte concentration would become depleted near the plates and the battery would appear to be discharged. Stirring the solution, would make for a much more uniform discharge curve.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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FWIW ... months.

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Interstate Batteries says no, but maybe they just want to sell more batteries:

also says no.

Matt Roberds

The "old husband's tale" was once valid, but is not any longer. Not that many years back, the standard container for lead-acid batteries was hard rubber. It was a good insulator and resistant to acid, and had the benefit of some resilience so the cases didn't crack or split at the seams. You might, with some luck, find an "antique" hiding in someone's garage and be able to inspect the casing of one of these beauties yourself, though most of yesterday's batteries have long since been recycled at the local lead smelter.

The danger of concrete was not electrical in nature but rather chemical. Lime (calcium) in concrete or cement could pass through the hard rubber compound whereas the acid could not. Cold wet concrete, not unusual for a garage or driveway, set up the conditions for the lime to actually leach into the battery casing, and it would, aided (I think) by the charged ions of the electrolyte egging it on. Battery activity requires a certain concentration of the acid, measured by its specific gravity. The lime would neutralize some of the acid, altering its concentration and producing a salt which would pollute the plates of the battery. The electrolyte would have to be purged and the salts washed out before you could put fresh acid of the proper concentration in-- just a pain. Further, because the lime got permanently into the rubber itself, it was less resilient on the bottom of the battery and was more susceptible to the same pollution at a later date. Hence the battery manufacturers would warn the service-station and garage owners to always rack their batteries and not store them on the floor once they had been "filled".

The military were the first to use acrylic and pvc cases for their batteries, which were often filled and ready for use many months prior to their actual use. When good strong pvc cases were economically feasible in the mid '50's (think Tupperware), the battery industry moved quickly away from rubber and into plastics. It was a good move, being at once cheaper and solving the lime-leach problem. The cases are also lighter and don't tend to expand or contract as much, important because the seal between the case and the terminal posts, which used to be a real bugaboo, is now truly tight. And the plastics transfer heat to the outside of the battery better (though now, with today's tight engine compartments, a battery over-jacket of foam rubber is sometimes needed to protect the battery from the heat of the engine!).

How long would it take for a rubber-cased battery's electrolyte balance to be upset (to the point where the battery's life was significantly affected) by lime leaching in? I have no direct experience, but would guess that a couple of months would be enough. But long before that, you would probably be able to measure a voltage drop in the cells, due to a less effective concentration of electrolyte-- possibly after a week or two. In the battery biz, where you have to take ambient room temp into account when measuring a cell's specific gravity, where .5v differential between (nom.2.2v) cells can be a cause for concern about the battery's health, little things can cause a big spoil.

Some of you old-timers in the telcom industry will probably remember glass jar casings for some of your huge central office batteries. They were taking no chances back then...

I don't, and I have never heard of this

Luckily no one told my electric fence battery about this, or it might have given up the ghost - it sits on the ground and 4 years on still works fine

David

Ah. Then anything which helped protect from the cold would be a good idea.

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    Dave Plowman        dave@davenoise.co.uk           London SW
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And this type of battery could be dismantled for repair. ;-)

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    Dave Plowman        dave@davenoise.co.uk           London SW
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Ken Weitzel wrote in news:vXcMe.27309$vj.437@pd7tw1no:

If the case is clean and dry before you set it down [most are NOT clean], there will be no such salts unless there is a crack in the case.

The 'salts' you see build up around the battery are due to spills of battery acid. When the water evaporates, it will leave behind lead sulphate and perhaps some other salts, depending on how pure the water has been that was added to the battery, over the years. You can also have copper sulphate from the wires leading to the battery corroding due to the acid spills.

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As part of PM I change 1 or 2 batteries a year... the price of owing too much stuff. I ALWAYS keep the freshest (old) batteries for emergency use with 12VDC powered radios. So I have done exactly the experiment you propose.

The old batteries sit directly on my garage floor. I never see any salts or other deposits on them.

Aren't all car batteries, even maint. free ones vented? I believe that along with the hydrogen gas a small amount of vaporized acid can escape from the battery's vent allowing it to settle on nearby surfaces such as the outside of the case.

There should be minimal gassing with a modern charging system. And most recent cars I've seen have a vent tube to take the fumes away from where they could do mischief in the event this occurs.

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    Dave Plowman        dave@davenoise.co.uk           London SW
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