[ausev] Cold weather and lead acid batteries

[Ken Thomas]

The batteries are AGM and both battery compartments are ventilated by 
large fans that are on anytime the charger is on.
The heater wire is generally not on while charging because the car was 
"heated" while driving. Additionally, the thermostats are sealed in 
adhesive heat shrink sleeveing.

Ken



-----Original Message-----
From: Steve Webb <stevenraywebb at gmail.com>
To: AustinEV News Announcements and General Discussion 
<ausev at austinev.org>
Sent: Wed, 17 Dec 2008 7:34 pm
Subject: Re: [ausev] Cold weather and lead acid batteries



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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