Rich Rudman wrote:
> What John is seeing is the 270 %80 DOD cycles. He is getting 2x out
> of the Yts that most of us are. And is paying for it rather fast.
> Now that it is cooler his range is dropping, and he needs some
> thermal support, and maybe a 15 Min splash and Go charge spot.

I just got back from visiting Minnesota Electric Supply, a local
electrical supply house. They have something I had been looking for for
years -- self-regulating heating wire.

This is a 2-wire cable about 1/8" thick and 3/8" wide. There are two
copper conductors, surrounded by a black conductive plastic insulation,
with an outer insulated coating. They have it in both 120v and 240v
versions. The conductive plastic produces about 5 watts of heat per foot
at 32 deg.F. However, its resistance goes up with temperature, so it
produces essentially no heat at 80 deg.F. It functions as if it were
made up of hundreds of little heaters, each with its own little
thermostat to turn it off when the temperature gets too high.

It is normally used for heating pipes, floors, electric blankets, etc.
But I think it may be a good way to heat batteries. Wrap a few turns
around your batteries, inside whatever insulation you can manage. For
more heat, use more wire. Since it is self-limiting, it won't overheat
if you insulate it too well, or runs across open spaces where it isn't
touching the batteries.

Price was $2.39/foot; they have spools of the stuff, and sell it by the
foot (though I'm not sure what the minimum purchase is).
-- 
Lee A. Hart                Ring the bells that still can ring
814 8th Ave. N.            Forget your perfect offering
Sartell, MN 56377 USA      There is a crack in everything
leeahart_at_earthlink.net  That's how the light gets in - Leonard Cohen

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