jackh@zehntel.UUCP (jack hagerty) (10/26/84)
> If I may tag along on your question, Dave, I have heard that > you should "never ever never" store a lead-acid cell on cement. This > will cause it to discharge. For the life of me, I can't think of a > reason... Anyone heard of this before, and know of a reason??? This "urban legend" has been around nearly as long as the storage battery. A few years ago one of the major magazines decided to put it to the test. (It was R&T, I think. It doesn't sound like something that C/D or MT would do. I'll look for the article tonight; if I find it I'll give a reference) Basically, the test went like this: they took two identicle batteries, fully charged them both, placed one on a plywood workbench and the other next to the bench on the concrete floor. After several weeks the batteries were tested and the state of charge was identicle, within measureable limits. If so, then why the "legend" in the first place? I can think of two reasons. First, batteries do discharge with time if they're not used. It's easy to put a battery on the floor in the corner of the garage and forget about it. When you go back (8 or 10 or more months later) the battery is dead! "Wow", you say, "that concrete floor sucked all of the electricity right out of this battery!" Second, concrete is a good conductor of heat as well as being a huge thermal mass. (Anyone who has stood around in the garage in winter will attest to this). This will certainly draw all of the *heat* out of a battery, at least down to ambient. Being chemical devices, batteries are much more sluggish at lower temperatures (right, snow belt people?). The above are pure conjecture on my part, but I've yet to see anything better. Jack Hagerty, Zehntel Inc. ...!ihnp4!zehntel!jackh
moroney@jon.DEC (10/29/84)
It probably worked like the evolution of a typical rumor in its formative stages, based on truth but... Probably what happened is something like this: Person "A" had a bad experience with a leaky battery ruining a concrete floor. He told person "B" "Never store a battery on a concrete floor, it will ruin the floor." "B" later advises "C" he shouldn't be storing his battery on the concrete floor because it is bad for it. C, knowing almost nothing about electricity, interprets "it" as the battery, not the floor. His imagination wanders a bit, and tells "D" that storing batteries on concrete floors discharge|ruin|doessomethingelsebadto the battery, and VOILA! One old wives' tale! Mike Moroney ..!decwrl!rhea!jon!moroney
jackh@zehntel.UUCP (jack hagerty) (10/30/84)
As promised last week, I looked up the R&T article where they tested this
myth. It was actually a two parter from "Technical Correspondence". I was
also surprised at how far back it was.
In the October '76 issue's TC a reader asked the same question that started
this discussion. The tech editor called a battery manufacturer who gave the
following explaination:
"In the early days of automobile batteries, circa the 1920s, battery cases
were made of wood. These would eventually saturate with the battery acid
allowing a current path if placed on a conducting surface. A concrete surface
allowed enough of a current trickle to completely discharge the battery in
a couple of days."
This explaination brought a hot letter from a reader who claimed that his
modern battery had discharged that quickly when placed on his garage floor.
To dertermine who was right, they (R&T) went to a local battery house and
conducted the following experiment:
They took two identicle batteries, charged them both, placed one on a
wooden bench and the other on the concrete floor next to it. Both the
state of charge and electrolyte density of all the cells of both batteries
was checked daily. After a week or two (I don't have the article with me)
the state of both batteries was identicle, within the accuracy of their
measuring instruments.
The second reader's letter and this experiment were written up in the
January '77 issues's Technical Correspondence.
-- Jack Hagerty, Zehntel Inc.
...!ihnp4!zehntel!jackh