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229Re: [hreg] FW: solar lawnmowers

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  • Kevin L. Conlin
    Jun 3, 2000
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      Hi James,

      Your theory on the self discharge is correct, however the mechanism was a
      little different. The actual reason, according to my battery expert, is as

      Before and during WW2 battery manufacturers made the battery cases out of a
      hard rubber material called ebonite. After the Japanese took over the
      rubber plantations of southeast asia and the Pacific islands, rubber came in
      short supply. In order to stretch their limited supply, the battery
      manufacturers started mixing small bits of flax and cotton in with the
      ebonite to act as a filler and conserve the rubber. These impregnated
      fibers were slightly conductive electrically. When a battery was left on
      concrete, the change in temp from night to day, and the batteries' high
      thermal mass would cause condensation under the battery, wicking up from the
      concrete. The conductive fibers in the cells would cause a slight short
      circuit between the cells in the battery, draining it. This was compounded
      by the fact that the batteries were not built as well as today's batteries,
      and they tended to self discharge faster anyway. The combination of self
      discharge and short circuits between the cells made the battery go dead very
      quickly. Thus, a battery stored for several weeks or months on a concrete
      floor would be completely dead, and ruined because of the resulting
      sulfation. After WW2, all the battery manufacturers converted to plastic
      cases, and the problem went away, forever, however the myth hasn't.

      I have to attribute this information to Foster Faerman at Tideland Signal,
      who knows more about lead acid batteries than anyone else I know. His
      father used to own a small battery manufacturing plant, and he literally
      grew up in the battery business. When I asked him about the myth many years
      ago, he reeled off the explanation quickly and succinctly, and it makes
      perfect sense to me. So there you have it, that's my explanation, but I
      liked your deductive reasoning as well. I wonder if anyone else can add to
      the unraveling of this myth.

      Best regards, Kevin PS How's the Solar Clubhouse coming? Will
      it be ready in time for football season?
      ----- Original Message -----
      From: James Ferrill <jferrill@...>
      To: <hreg@egroups.com>
      Sent: Friday, June 02, 2000 9:04 PM
      Subject: Re: [hreg] FW: solar lawnmowers

      > Right. On the sci.chem.electrochem.battery newsgroup a number of months
      > we had a big thread going on to hash out the myth. The best that anyone
      > up with was back after the turn of the century, batteries were made of
      > boxes lined with tar paper. If you set this on a concrete floor and the
      > battery leaked a little (which was fairly common), a conductive path would
      > set up that would drain the battery. Concrete reacts really well with
      > acid. I still know people who won't put a battery on the floor unless it's
      > setting on a piece of wood because of that myth.
      > James
      > "Kevin L. Conlin" wrote:
      > > The myth about batteries and concrete is that by leaving them directly
      > > top of a concrete floor, the concrete "drains" the charge out of the
      > > battery. This hasn't been true since WW2, but a lot of people still
      > > by it since their father or grandfather drilled it into their heads.
      > > of them can ever explain why this will happen, since it normally rests
      > > conductive metal in a car, but they will adamantly swear it's true.
      > >
      > > ----- Original Message -----
      > > From: s askew <rsaskew@...>
      > > To: <hreg@egroups.com>
      > > Sent: Friday, June 02, 2000 10:49 AM
      > > Subject: Re: [hreg] FW: solar lawnmowers
      > >
      > > > I am not sure what the myth about batteries and concrete is, but
      > > > from my experience a battery that leaks at all will begin to eat
      > > > the concrete. I now store batteries in a plastic tub and have
      > > > added some baking soda at the bottom hoping to neutralize any
      > > > acid that does leak.
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