Re: Helping the batteries perfom in the cold.

["David Roden" <roden ald net>]

From:                   "Max Hall" <maxo iname com>
To:                     "elec-trak discussion list" <elec-trak cosmos5 phy 
tufts edu>
Subject:                Helping the batteries perfom in the cold.
Date sent:              Sat, 2 Jan 1999 19:32:35 -0500

> Next question to all you battery-powered people:

(Energizer bunny?)

> 
> 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?

Yes.  Every battery has a thermal capacity curve.

> 
> 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 and yes.  They hold heat mainly because they are massive.  Every 
battery has internal resistance, so they generate heat as they work 
(though I'm not sure it's very much, given the relatively relaxed rate at 
which the ET asks them to work).

> One would, in an unheated garage, want to be very careful about 
> ventilation
> especailly during charging, of course.

Someone may disagree with me, but I'm of the opinion that most domestic 
garages are large enough (and leaky enough) that hydrogen buildup is not 
really a concern, given the number of batteries and the rate of charge an 
ET uses.  I don't have any special garage ventilation provisions for 
either my ET or my electric car -- although I used an induction motor 
blower to exhaust the air from the car's battery boxes when I had flooded 
batteries in it; a car is much smaller than a garage.

I can see that you'd be more concerned in a heated garage, especially if 
the heating system used a standing pilot.  But unlike gasoline fumes, 
which are heavier than air, hydrogen would collect (if it collected at 
all) near the ceiling.  I think.

I just can't see six golf car batteries evolving enough hydrogen to worry 
about, as long as it's not held captive in a small space.

Anyone have any other thoughts?

PS: I wish the person in charge of this mailing list would program it so 
that the reply-to field in each message contained the posting address for 
the list.  If I forget and just click "reply," the reply goes only to the 
posting contributor, rather than to the entire list.  I bet we all miss 
some good, interesting stuff that way.

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