# EV Performance at or below freezing



## wasatch (Jun 25, 2009)

I have often wondered what kind of performance I could expect from a EV when the temperature falls at or below freezing.  What if the EV is parked outside in these temperatures , like during work hours.


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## dimitri (May 16, 2008)

All depends on how much below freezing the battery gets and what type of battery you have in the EV.

Lead Acids don't work well below freezing, Lithiums work, but performance depends on many factors, most importantly how much below freezing it is 

Most people up North insulate their battery boxes, and/or heat them up with additional heating elements, which of course means less energy to the wheels and less range.

Once you start moving, current flowing thru the pack tends to warm it up a little. Also, if you are charging while parked, charging current also warms them up a little, but again, all depends on how cold it is.

Luckily, I can't speak from personal experience, since I am in Tampa


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## PatricioIN (Jun 13, 2008)

My batts are not heated or insulated. I knew it would decrease my range in winter but decided to live with it for my first conversion. I live in Indiana and it often gets below freezing in winter. The car actually performed fine, but range was drastically cut... In our 70-90 degree weather now, I can go 40 miles. In dead of winter it can be as low as 15 miles on a VERY cold day, but is typically around 20 miles on average.


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## Coley (Jul 26, 2007)

Last winter I ran my 72 volt system on 15 degree days with no problems.
This was using fla marine deep cycle batteries (not a good choice).
The car sat out in an open ended shed, now I have a new unheated building.

I don't insulate or heat my batteries (a little morning charging heat is all).

I only have to go 5 miles or so, so range is not a problem.

This year I am running MK Gel batteries and they are performing very well.

I try to run all winter long, but some snowdays makes too much to push through. 

They will be tested this winter to see how well they will work for me.


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## simey_binker (May 13, 2009)

simply run off-the-shelf battery heaters off the charging circuitry. that is, when you have the car parked and plugged in, the batteries are both charging, and being heated to above zero. 

when you drive, the amp draw will keep them warm enough for operation, therefore there is no "waste energy" going towards heaters when driving.

the only issue you run into, is when you park the car for a while, without plugging it in. in that case, you may want to hook up a switch to run the heaters off the traction battery; but this counts as loss.

Sim


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## tomofreno (Mar 3, 2009)

No experience yet myself, but there's this:
http://www.geocities.com/RainForest/Vines/5565/heat.html


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## DaveAK (Jun 28, 2009)

OK, so don't laugh, but what about -20F/-30C? 

I don't hold out too much hope, but I'll be insulating well, adding heaters, and it will plugged in at work as well as overnight. I don't have much of a commute so if I could get 40mph/6miles it would be OK. And if I can't get down the low I'll just drive something else over the winter.


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## RKM (Jun 9, 2008)

DaveAK said:


> OK, so don't laugh, but what about -20F/-30C?
> 
> I don't hold out too much hope, but I'll be insulating well, adding heaters, and it will plugged in at work as well as overnight. I don't have much of a commute so if I could get 40mph/6miles it would be OK. And if I can't get down the low I'll just drive something else over the winter.


I don't have first hand experience, but from what I've read, you should be okay. Yes, Pb performance really suffers with cold. REV Consulting in Ottawa, Canada has done some testing on a couple of different conversions. The vehicles had insulated and heated batt boxes as you are suggesting. I don't remember the specifics of the testing but the results were quite encouraging. Range performance was reduced amazingly little even at very cold temps. IIRC it was less than a 10% reduction, even at -30C. Keep the batteries warm and they should have the capacity they have in summer.

Of course, any vehicle's economy will be reduced with cold weather (rolling resistance, oil viscosity, etc).

Rob


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## tomofreno (Mar 3, 2009)

Could you give a reference for this work? I will be operating in 5 - 30 F temperatures in winter. I plan to use 1/2" insulation in the boxes and heaters. I would really like to see the details of how they operated at temperatures in the range of -22 F (-30C).


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## RKM (Jun 9, 2008)

tomofreno said:


> Could you give a reference for this work? I will be operating in 5 - 30 F temperatures in winter. I plan to use 1/2" insulation in the boxes and heaters. I would really like to see the details of how they operated at temperatures in the range of -22 F (-30C).


 
There you go.

http://www.revconsultants.com/winterizing.html

Rob


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## Zemmo (Sep 13, 2007)

I bought my car from a guy up on Illinois/Wisconsin border. He had battery heaters on the batteries. I live in Texas where cold isn't an issue. So when I was cleaning the battery racks and repainting them I pulled the battery heater system out. I have it for sale in the classifieds section:

http://www.diyelectriccar.com/forum...y-warmer-controller-termostate-150-31177.html

All I have is just the thermostat controller and display. I don't have the pads any more. They were weathered since they were out in the open and not in a battery box. But he said this system worked great for him. Just plug it into the wall while you are charging or if you know it will be cold out. It has a temp prob to heat them up to a point and not over heat them. Having it in a battery box would probably make this system even better.


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## DaveAK (Jun 28, 2009)

Well that's really encouraging! Thanks for the replies.


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## martymcfly (Sep 10, 2008)

I read somewhere that someone was using waterbead heaters for his battery pack.


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## 86Honda (Apr 15, 2009)

Waterbed heaters should work well - they are usually thermostatically controlled and waterproof. My original 96 volt (12 V x 8) FLA battery pack was in a box (well, the rear half was) but unheated, and Indiana weather killed them. Range went from 30 at most in the summer to 10 or less in the winter. I don't drive it much in the winter becasue of that. This past winter it got down below -20 F and when I checked on the batteries this spring, 3 of them had exploded from freezing. Soon my LiFePOs will be here, and no more watering, excess weight and charger GFI problems...


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## DaveAK (Jun 28, 2009)

A fully charged battery shouldn't freeze. Luckily I will be able to put my EV on charge at work. (Every parking space has an outlet for employees to plug in their block heaters.)


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## tomofreno (Mar 3, 2009)

You might still need to heat if you want to maintain similar range in winter and summer. The LiFePO3 cells don't take a charge well below 30 F. I'm told they will only charge to about 60% of their capacity at that temp. I imagine they charge considerably less at -20 F. The SkyEnergy spec for charging is 0 C (32 F) to 55 C (131 F). If you have more than enough capacity then maybe you can avoid heating. I plan to start heating maybe an hour before, and during charging (since I'm told LiFePO4 cells don't get warm at charging currents below 1C, C as in Capacity). We'll see...

Tom


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