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Re: Helping the batteries perfom in the cold.

Charging and discharging batteries are not both exothermic; one is
endothermic, but I don't know which off the top of my head.  What works in
our favor for cold weather is that any battery current supplies some
electric resistance heating.  I charge my batteries for 15-30 minutes
immediately before use in cold weather to warm them up.
-----Original Message-----
From: darrylmcmahon igs net <darrylmcmahon igs net>
To: elec-trak cosmos5 phy tufts edu <elec-trak cosmos5 phy tufts edu>
Date: Sunday, January 03, 1999 11:24 AM
Subject: Re: Helping the batteries perfom in the cold.

Hi Max,
> To help my E15 work well out there in the cold, does it not make sense to
> keep the thing as warm as toast (ok, say, 65 degrees F) before I put it 
> to
> work?
> I imagine that those big bad batteries have huge heat capacity, (I mean,
> specific heat of lead is high) and that they will cool very slowly if 
> they
> come out of the garage at 65. (ANd operation is exothermic; they give off
> some heat as they work, yes?)
Yes, charging and discharging are both exothermic.  It is not
necessary to
keep the whole tractor warm, just the batteries.  The motors would
rather be cold.  Look into getting an automotive battery blanket
(usually 50 or 80 watts heating elements).  Put one under the front
batteries and one between the rear batteries.  Putting a thin sheet
of styrofoam over the batteries (in place of those black plastic
battery covers) should also make a big difference in terms of heat
retention.  I use this arrangement in my electric car, and it works
well in temperatures to -35 degrees.  Batteries have remained at
+70 degrees F with no difficulties.

> One would, in an unheated garage, want to be very careful about
> ventilation especailly during charging, of course.
Unless you have an airtight garage (unlikely in my experience) and an
open ignition source beside and above the batteries, I would not be

Darryl McMahon             48 Tarquin Crescent,
It's your planet.         Nepean, Ontario K2H 8J8
If you won't look         Voice: (613)828-0805
after it, who will?       Fax:   (613)828-3199