Myth - Batteries Discharge on Concrete

Mark from Sahuarita Manager Posted   Latest  
Discussion
Electrical
Myth

Myth - Car batteries Discharge on Concrete - battery must be charged and stored on a wood board.

Come on...really. Batteries back in the day sat on a steel plate in the car. How do the electrons make their way thru plastic or the old rubber based battery cases?

Speculation on source - Battery charge and power delivery are very dependent on temperature. In colder climates, sitting on cold concrete would compromise charging and power delivery efficiency.

Zero time to figure this on out. But techs I worked with were absolutely convinced this was true. When questioned about how this was technically possible; they had no explanation.

I wonder if this myth still is out there.

Mark …

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Rick from The Woodlands

 

Diagnostician
 

Mark,

Car batteries used to be encased in hard rubber, a substance that was porous enough that battery acid could seep through it and create a conductive path through the damp concrete, draining the battery. The "myth" is actually the truth from another era/battery design.

snopes​.​com/fact-check/bat…

HTH

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Chris from Commack

 

Diagnostician
 

Yes this used to be true, but the myth still persists today. It was "taught" to me when I first started 20 years ago. It was treated like gospel, all batteries were on the battery rack, on wooden blocks.

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Mark from Sahuarita

 

Manager
 

I have a great deal of respect for snopes. But I still don't get it.

Is the concrete floor a low level short..,to ground? Between the plates? The electrolyte is always between the plates.

Why doesn't the metal plate the battery is mounted on in the car do the same?

Technically how does this work? Where is the current path?

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Tanner from Wellford

   

Instructor
   

Something that I have always wondered and unfortunately never had an answer to is can condensation form inside a battery? I can tell you after having most of my property in a storage unit for the last two years that condensation can form inside plastic totes. I would assume sitting on a cold concrete slab could cause this to happen more frequently.

If condensation was able to form inside a battery it would dilute the electrolyte with water which would result in diminished battery performance. It would take a rather long time for this to happen but i Suppose it may be possible.

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Chris from Commack

 

Diagnostician
 

Where would the condensate come from? wouldn't the humidity level already be high in the battery? I would like to think that even though vented, the "airflow" would be low, and the condensate would be from the acid/water mix. If anything the humidity from inside the battery would exit from the battery faster than humidity would get in. Well, unless the battery is underwater. I honestly don't know the answers to these questions. Great thought experiment.

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Tanner from Wellford

 

Instructor
 

Because the battery is full of water that would make it more prone to condensation. It would basically be the same as a plastic bottle getting condensation inside it. The low airflow inside a battery would also make it more likely as the more airflow you have the less likely condensation is to form, the less airflow the more likely. Also humidity may not exit the battery if the dew point is outside is high.

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Mike from Fresno

 

Instructor
 

It is. More prevalent among people our age.

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Jim from Southampton

 

Mobile Technician
 

I don't know about that, I've been told by A LOT of techs that MARK WARREN taught them that one night in a bar ??? So it must be true. LMAO

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Thomas from Manassas Park

 

Technician
 

Im with you on this one mark. I was told that since concrete is colder than the battery itself the temperature is what drains it. To that I say what is the difference of a battery that sits on a metal hold down plate in a car when the outside temp is below 32 degrees?

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Jim from Frederick

 

Curriculum Developer
 

Can a battery with dirt and moisture across the top discharge faster than a clean battery?

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Mark from Sahuarita

 

Manager
 

Jim - not sure about dirt and moisture.

But you can measure the voltage draining across the top of a battery with electrolyte spewed on top.

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Jim from Frederick

 

Curriculum Developer
 

Agreed. Then if early case designs were semi-porous this can happen on the bottom of the battery, especially depending on what it is sitting upon. That was how this was explained to me during the tour of a battery manufacturing plant with a product engineer when someone asked the question. Modern materials and tech have eliminated the potential. (HA! Electrical joke!) ;)

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Mark from Sahuarita

 

Manager
 

The voltage I have measured on top of the battery travels from the negative to positive post thru the electrolyte connection. 

Not sure I buy the porous rubber case theory. But let's assume it is true.

What is the current path? Post to Post? Like on the top?

If it is thru the bottom, placed on concrete, how is this a better conductor than the metal plate it is mounted on in the car? If it is thru the bottom and not post to post I still don't get the current path.

If there is a current path cell to cell thru a porous rubber case; wouldn't the shortest path be thru the case between the cells and not the bottom?

Not claiming to be right. Just stating that I don't see how this would work.

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Rick from The Woodlands

 

Diagnostician
 

Mark,

Here another explanation that may shed some light.

homepower​.​com/articles/solar…

HTH

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Mark from La Junta

   

Engineer
   

Mark

I spent decades as an automotive research engineer. Through the years I was able to be in the same room with some extremely intelligent and knowledgeable men and women (not always other engineers). I remember being told (by a battery engineer) that his dad (or relative) worked in the military procurement area (huge warehouses and stockrooms). Evidently, back in or around the second World War; flooded, lead/acid batteries were stored on the concrete floor (in warehouses) and stacked a few levels high (with those thick cardboard separators between the batteries) very much like today. Evidently, when stored in this configuration they would often find the lowest level of batteries were drained. Usually it was after the front row was removed and the lowest layer of cardboard was hanging there. Warehouse personnel would "toss" the bottom layer of dead batteries then next time use a wooden pallet or other separator between the concrete floor and the lowest layer of new batteries and amazingly, the new batteries didn't seem to be drained. SO, the "ASSUMPTION" was you couldn't stack/store batteries on concrete. A really sharp guy or gal was curious about yours and my tax dollars being "thrown away" on dead batteries and investigated. What they found several years later was that when the military used the fire hose to clean the warehouse floors, they got the cardboard separators wet. The wet cardboard separators then very slightly/slowly conducted battery voltage to the concrete and YES, they did drain the batteries. Just our luck the "myth" was already spread by then throughout the military (and therefore the country as our military men and women came back to civilian life). It was probably documented in military memos.

How many of us can think of incorrect information that we held as a "truth" because it seemed logical? How about the whole charge/discharge myth of NiCad batteries (which was based on power curves from our space station?) Later we found that battery data to be incorrect but by then many of us were already discharging/charging our NiCad based on what seemed logical?

We could go on and on with facts, then the stories about those facts (usually the stories are more interesting, but not true)

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