[ausev] Cold weather and lead acid batteries

[Steve Webb]

A little word of caution using "pop switch" tstats in a lead acid battery
compartment, the  gases produced during charging can be flammable,
corrosive and explosive under the right conditions.  Pop switches can
produce sparks.
NEC Article 625 covers the external equipment to an electric vehicle that
connect an electric vehicle for charging purposes.
A good rule of thumb is if you can smell the batteries charging you need to
ventilate it.

Steven Ray Webb
Texas Master Electrician 19870





On Wed, Dec 17, 2008 at 8:01 AM, Ken Thomas <kenscircus at aol.com> wrote:

> I got some resistance wire, 25' of HWR-21168 from
> www.refrigeratorparts.com and a couple pop-switch thermostats, stock
> number 802-STO-60, from www.mouser.com.
>
> All 25' of the resistance wire was snaked around the batteries.  The
> batteries are split into two compartments so a thermostat is installed
> in series with each section of resistance wire.  Each compartment gets
> 1/2 of the 25' but it is all wired in series.  So, either thermostat
> will turn the whole thing off.
>
> The heater wire system draws 1.9 amps at 120 volts or 228 Watts.  The
> wire is 2.5 Ohms per foot.  The thermostats will keep the compartments
> at about 50 degrees Fahrenheit.  Still a bit cool but much better than
> 30 degrees.  It will never turn on above 50 degrees.
>
> The 1.9 Amps is low enough that it can be paralleled across the charger
> input without undue mains load while charging.  I just leave it plugged
> in all night (which I always do anyway) and it keeps the batteries from
> getting lethargically cold.
>
> Thanks,
>
> Ken
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