[Oeva-list] FW: Battery Warmer Sources

[Graunke, Gary]

forgot to cc the list...

-----Original Message-----
From: Graunke, Gary 
Sent: Friday, January 15, 2010 10:47 AM
To: 'Dick Burnham'
Subject: RE: [Oeva-list] Battery Warmer Sources

One needs to be specific to the chemistry and even the specific product. Some are high power and don't heat up--lower power ones will for the same currents. 

Li Ion with Cobalt (eg, early ThunderSky cells) are very exothermic (discharge reaction produces heat) during discharge, but endothermic (the charging reaction absorbs heat). Of course, if you have too much current (go beyond the power ratings) the batteries will heat up for both operations. 

Lead batteries heat up during charge.

NiMH heats up in both directions a lot! 

What you need is to measure the internal resistance for charging and discharging as a function of the ambient temperature. 

I have some data for LiPO4 A123 cells in my car, and as a result I don't heat or cool them. But most LiIon batteries need cooling or they will go into thermal runaway and catch fire. (I had a bunch of blowers to do this). 

But it all depends on your chemistry again and the power rating of the cells vs your car's power demands and charger power. 

I have power supplies, electronic loads, and data acquisition test equipment to evaluate this for batteries (but no chamber to control the ambient temperature). I also don't have an automatic cycling control unit, so it is a manual process. 

The same issues apply to battery internal resistance as a function of ambient temperature.

Gary

-----Original Message-----
From: oeva-list-bounces at oeva.org [mailto:oeva-list-bounces at oeva.org] On Behalf Of Dick Burnham
Sent: Friday, January 15, 2010 10:25 AM
To: Hansen, Chris; Daniel Anolik; Pete Skeggs
Cc: Oeva-list at oeva.org
Subject: Re: [Oeva-list] Battery Warmer Sources

I would be interested in a discussion of the same questions but in regards to LiFe4po cells.  Also, how about cooling on Lithiums while charging?  Needed?

Dick

-----Original Message-----
From: oeva-list-bounces at oeva.org [mailto:oeva-list-bounces at oeva.org] On Behalf Of Hansen, Chris
Sent: Friday, January 15, 2010 10:18 AM
To: Daniel Anolik; Pete Skeggs
Cc: Oeva-list at oeva.org
Subject: Re: [Oeva-list] Battery Warmer Sources

I am not having major problems with my lead acid batteries although I do notice some loss of range. Not more than 20%. I charge my vehicle in my garage where the temp never gets below 50 Fahrenheit. Couple of questions:

What is the typical efficiency loss of lead acid batteries in the winter at say, 50 Fahrenheit? At what temp does the loss kick in and is the loss mainly during charging or during use?

Chris

-----Original Message-----
From: oeva-list-bounces at oeva.org [mailto:oeva-list-bounces at oeva.org] On Behalf Of Daniel Anolik
Sent: Thursday, January 14, 2010 6:30 PM
To: Pete Skeggs
Cc: Oeva-list at oeva.org
Subject: Re: [Oeva-list] Battery Warmer Sources

Hi Pete,

I used to drive an electric Geo Metro with lead acid batteries, and battery warmers. The conversion was done by Dave Cloud up in Washington, and he came up with a cheap, but affective warming solution that kept my Geo running through the coldest of Portland winter days. Here's how it worked:

- Start with an electric soil heating cable, which are usually intended for heating flower boxes in cold weather, or for growing tropical plants. A quick internet search shows multiple options for around $35, including a thermostat.
- Snake the heating cable back and forth along the bottom of your battery box, under the batteries.
- Install the thermostat in the same battery box, but on top of the batteries.
- Power the heating cable off of the AC line, when the car is plugged in for charging.
- Optionally install a toggle switch on the dashboard for disabling the whole system (in warmer weather)

The result was a heating system that only ran when the car was charging, the batteries were colder than 70F, and the dashboard toggle switch was enabled.

Enjoy,
Dan


On Jan 14, 2010, at 1:34 PM, Pete Skeggs wrote:

> Hi folks,
>
> The lead acid batteries in my 2007 Zenn are struggling to get through
> this weather.  I'm trying to stretch their lives as long as possible
> as I don't want to replace the whole pack (6) right now if I can help it.
>
> I've heard that battery warmers can help significantly.  I'm sure you
> can walk into a Napa Autoparts store in Colorado and pick a few up
> anytime you want, but I'm guessing they're not in big demand here.
>
> Anyone recommend a good source that's local, or else online?
>
> -Pete
>
> _______________________________________________
> Oeva-list mailing list
> Oeva-list at oeva.org
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