# real world lithium and cold weather



## scott (Feb 15, 2009)

I'm looking for some real world results with lithium packs in the winter. I currently am using a 3year old 144v 140ah agm pack. When new was getting 20miles in the summer and 12miles in the winter. This last winter I was going 14miles and charging at 7miles each way. Currently I'm getting about 12mile range per charge. But now my employer has decided that I can no longer plug in there. The tempature here ranges from +90F in the summer to -10 in the winter. So, what is being seen for range differences from summer to winter with a lithium pack?


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## bjfreeman (Dec 7, 2011)

yes @ -25C is the lowest you can go and have practical charge.
once you get to -45C the max charged voltage is about 3.0 V instead 3.4v per cell of 55C where the knee is about 90% SOC.
@-25C the knee is about 70% SOC (2.8V) and max charge voltage is 3.2V Instead of 80% at 25C max charge 3.3V.

This is similar problem with lead acid, however you can use a battery heater with a ICE that is charging, but it drains the battery pack EV.

my pack is liquid cooled and heated. the ,motor liquid cooling is it channel in the winter to keep the batteries warm.
for EV you would add a battery warmer to the charging circuit, so while charging, the batteries are warm.


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## mora (Nov 11, 2009)

I have not noticed much difference in range but voltage will sag way more if batteries are cold. Temperatures drop down to -35C here. I could go 60km during summer and 55km during winter. Performance is worse because of sag. But not much.

Batteries tend to warm themselves up; if voltage drops and amps are high batteries get warmer. When they get warmer sag will lower (assuming those are not near empty). Charging also warms them up a bit but you should not charge if batteries are below zero celsius. That's why you should add battery heating. It should be no problem if you plug in right after drive (as batteries are likely warm enough).

You should also insulate your battery cases. That's good idea to do when adding heating. I don't have heating but have insulated all my battery boxes. Batteries stay above zero celsius for ~24h in -20C weather.


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## batterytang (Nov 17, 2011)

Alll battery would be effected by temperature,

Including Lithium batteries.

I think for a better solution, take cooling system and

heating system would be a good choice.

I do not think electric car can replace gas car,

Only for some suitable weather(not very cod or hot),

and some regular range mile driving.


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## batterytang (Nov 17, 2011)

Inside the battery is a chemical balancing system.

So you will know how important a player that temperature act.


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## 3xe-electric-cars (Jun 7, 2012)

In cold weather (below zero Celsius) it is good idea to heat batteries especially before charging.

To hold the working temperature higher than 0 Celsius you could use resistance wire - the same like antifreeze heaters used. An example:
http://www.omega.com/ppt/pptsc.asp?ref=SRF3_SRF5_SRF8&Nav=heab01
Great advantage if these cables is self protection from overheating (resistance rises with temperature).
You can wrap battery cell 2-3 times to have enough heat for every single cell.

Remeber, that high voltage DC systems need special relays with anti-arc protection (vacuum, magnetinc, etc). Without this kind of protection your heater could stay always ON.
You could also use some simple manual switch only in winter.


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## lowcrawler (Jun 27, 2011)

bjfreeman said:


> yes @ -25C is the lowest you can go and have practical charge.
> once you get to -45C the max charged voltage is about 3.0 V instead 3.4v per cell of 55C where the knee is about 90% SOC.
> @-25C the knee is about 70% SOC (2.8V) and max charge voltage is 3.2V Instead of 80% at 25C max charge 3.3V.


So as the temp drops (it's below 0C here for about 4-5 months straight every year) I need to recalibrate my BMS shunting levels and charger shut-off points?

This is the first I've heard of this... and would have significantly impacted my plans. 

Can you tell me more?


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## scott (Feb 15, 2009)

mora said:


> I have not noticed much difference in range but voltage will sag way more if batteries are cold. Temperatures drop down to -35C here. I could go 60km during summer and 55km during winter. Performance is worse because of sag. But not much.
> 
> Batteries tend to warm themselves up; if voltage drops and amps are high batteries get warmer. When they get warmer sag will lower (assuming those are not near empty). Charging also warms them up a bit but you should not charge if batteries are below zero celsius. That's why you should add battery heating. It should be no problem if you plug in right after drive (as batteries are likely warm enough).
> 
> You should also insulate your battery cases. That's good idea to do when adding heating. I don't have heating but have insulated all my battery boxes. Batteries stay above zero celsius for ~24h in -20C weather.


Do you remove any of your insulation for the summer?


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## onegreenev (May 18, 2012)

scott said:


> Do you remove any of your insulation for the summer?



No. Unless your cells or box are directly in the path of the sun. If they are under the hood somewhere that heat can escape then you should be fine. I drove my Leaf in summer and winter and I can tell you that you will loose range in the winter. I tested a cell as low as -56 below zero f and put the cell to sleep. The cell is fine after it thawed and once the cell is above 0 degrees F it will begin to take on a real charge. It is best once its around 32 degrees F. If you can keep your cells at around 70 degrees F then your going to do well. My cells are in the chassis and even in the winter and sitting in the hot summer sun and outside temps hitting 106 F and the car sitting on asphalt parking lot for 8 hours I have never had the battery pack temp go near the danger zone for being overly hot. 

The cells are affected by cold Sorry but it is a fact. 

Pete 

Freezing the cell only puts it to sleep. It goes into a natural hibernation mode. Wakes up easy too.


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## Kamleshgk (May 24, 2012)

Apparently the Swedish company Volvo has an electric car - C30 Electric, which uses an ethanol based gas heater to warm the cabin and the pack.

I blogged bout it at my site
http://www.pluginindia.com/1/post/2013/12/electric-vehicles-and-cold-weather.html

I want to know, if EV conversions can use a gas based heater to warm the battery and the cabin instead of using the energy from the battery.
Is that feasible? Would it be worth it?


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## mora (Nov 11, 2009)

scott said:


> Do you remove any of your insulation for the summer?


Sorry for late reply. I made top parts of insulation removable so I can take them off during summer. I tried driving with them in place and batteries were a bit too warm for my liking after driving and charging. Like +30C and over all the time. I haven't seen any need for external cooling though.


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