Loss of range in cold weather

[TomMoloughney]

There have been a lot of threads and comments here about the loss of range now that the cold weather has arrived. This is my 6th winter driving electric and every year this issue comes up around mid to late November. The range is going to be significantly less in cold weather regions, perhaps as little as 45 to 50 miles per charge depending in on conditions, so prepare for this and use techniques to maximize your range. This isn't a problem specific to the i3, all electric vehicles have this problem because the batteries just don't work as well when they are cold. I have gotten so many emails and private messages this year that I did a blog post to try to clear the air about it. There are a lot of i3 owners that believe their specific car has a problem or the dealer changed their software and that's what the range is lower. That isn't the case, it's just the cold weather. Here are some recommendations to mitigate the problem. Spring is only 4 months away, your full range is waiting there for you!

http://bmwi3.blogspot.com/2014/12/bmw-i3-psa-no-there-is-nothing-wrong_8.html

 

[websterize]

It's too bad BMW didn't install a heated steering wheel, as in the Leaf.

Wearing a down jacket ( ), and sitting atop those toasty heated seats and holding a heated steering wheel, I'd could probably drive all winter without using ventilation heat. (I precondition during the work week.) The heated wheel probably draws much less power than the heat pump, and the wheel is literally more direct, more efficient, heating.

I bet we have a heated steering-wheel option in MY 2016.

 

[WoodlandHills]

Am I the only one who finds it funny that in 2014 the most advanced car on the road requires the driver to dress up like he was doing the London-to-Brighton Run? Perhaps BMW should sell high tech car coats and lap rugs as accessories?

I wonder if a small propane heater from our camping gear would keep the cabin warm while extending the range. The ventilation system would keep the cabin free of CO just like it removes smoke.... You could fold the back seat and strap it down to the cargo rings. It would pose no more explosion hazard than packing your camping gear in the car for a weekend trip.

 

[BrianStanier]

The ventilation system would keep the cabin free of CO just like it removes smoke....

It might - or it might not. I would suggest a canary would be an essential extra.

The electrical heater is 5.5kW. That's two standard propane cooking rings. Quite a lot of heat.

 

[Simon]

I live in holland, since the beginning of september i have significantly less range than before after a workshop visit. Before the visit i had 19,6 kwh battery capacity and steady, since then it was 18,1 and dropping, then steady 17,5. The steep drop was beginning september and the workshop performed a software update. Temperatures in holland were above 20 degrees still. In the mean time we have around 4 degrees celsius, and batcap now 17,1.

Tom, do you think i am imagining?

 

[Blue20]

Simon, how do you find out the battery capacity?

I tried turn off heater. It does increase the range a bit, but the windows will fog up.

I understand in cold weather the batteries will output less juice. However, even if I turn off heater, I still can't get the efficiency anywhere need in the summer. What else may be taking up the juice in the background?

 

[alohart]

Am I the only one who finds it funny that in 2014 the most advanced car on the road requires the driver to dress up like he was doing the London-to-Brighton Run? Perhaps BMW should sell high tech car coats and lap rugs as accessories?

I agree! There have been small gasoline/diesel/alcohol auxiliary heaters available for years. Especially for REx versions that already have on-board gasoline and don't have a heat pump heater, offering one of these auxiliary heaters would seem to be a no-brainer, but no EV maker is doing so. Several i-MiEV owners have installed these heaters and have reported much improved winter range and much more civilized driving (i.e., no need for 12 v. electric blankets, electric socks, etc.).

 

[mindmachine]

Am I the only one who finds it funny that in 2014 the most advanced car on the road requires the driver to dress up like he was doing the London-to-Brighton Run? Perhaps BMW should sell high tech car coats and lap rugs as accessories?

I wonder if a small propane heater from our camping gear would keep the cabin warm while extending the range. The ventilation system would keep the cabin free of CO just like it removes smoke.... You could fold the back seat and strap it down to the cargo rings. It would pose no more explosion hazard than packing your camping gear in the car for a weekend trip.

I agree with you a lot of the time, but really, really? How would you like to own a Tesla S with a 85 kwh battery pack and loose range from a stated 250 miles down to 170 miles or so? It is state of the art and battery technology is what it is at the current time.

Anyway today I took a 103 mile trip, preconditioned in my garage which is at 45 deg F with a projected range of 88 miles and pre conditioned when I left. I drove 103 miles starting out at 10 am at 35 deg F and driving 103 miles over 5 hours with 4 stops and 45 deg F on the returne home. I registered 77 miles full EV and 30 miles with my Rex upon arriving home, slightly less than a gallon of gas, this was in ecopro+ mode driving on state routes at speeds of 50 to 60 MPH and with an elevation change starting 1000 ft above sea level up to 1250 ft back down to 800 back up to 1250 and then back down to 850 and back up again to 1230 and again back down to 800 then up to 1300 qnd down again to 1000 up again to 1250 and down again to 1150 for one way and then the repeat backwards to home.

While I admit I have only 800 miles on my i3 but I am still getting good range, however in the late summer I would have been able to do the whole trip in EV in ecopro + mode and that translates as a 25% drop in range. Thank God fir the Rex at least for me, no EV charging in Walnut Creek Ohio.

 

[TomMoloughney]

I live in holland, since the beginning of september i have significantly less range than before after a workshop visit. Before the visit i had 19,6 kwh battery capacity and steady, since then it was 18,1 and dropping, then steady 17,5. The steep drop was beginning september and the workshop performed a software update. Temperatures in holland were above 20 degrees still. In the mean time we have around 4 degrees celsius, and batcap now 17,1.

Tom, do you think i am imagining?

I don't think your imagining, I just believe you'll see the capacity raise in the spring. There will be a gradual capacity loss for every battery, that's inevitable. But I think you'll see more like 2-3% per year, not what you've reported here. The cold weather really effects the battery. I've been through this for five winters now and every year there are a lot of people that swear their car has a problem, whether it's a bad module or there was something done at a service visit that is causing the range problems. Then spring rolls around and suddenly the range goes back to what it was the year before. I have no idea if you car really has a problem or not, but my guess it that is probably doesn't. Your dealer should be able to check everything out. If they do and say everything is operating the way it should, then my bet is that is is fine, and the range loss is due to the colder temperatures.

 

[fdl1409]

This "capacity loss" to 17.x to 18.x kWh in the service menu is due to a software update, as we have concluded in the German i3 forum. BMW after several inquiries conceded that this is the case. They promised a software update to fix the problem.
My REx has not been updated yet. In the summer my max. capacity was around 19.7 kWh. It has suffered somewhat from the cold, but nowhere near those quoted figures. My lowest max. capacity so far was 19.2 kWh. On saturday after a longish trip battery temp rose to 15°C, after that the service menu showed a max. capacity of 19.6 kWh again. Yesterday 19.4 at a battery temp of 7°C.

I am living in a rather cool region, colder than the Netherlands. Minimum temperature was -5.7° this winter ( 22F ), rather mild for us. Lowest battery temperature was +1° ( 34F ). So far in december temperatures remained in a range between +3 and -3°C.

Average power consumption from the meter, including all losses:
- summer june/july/august : 13.4 kWh/100km
- autumn september/october/november 14.6 kWh/100km
- winter december ( 320 miles ) 16.6 kWh/100km

Moisture is a factor just like temperature.
Last week with temperatures around freezing point and the roads always wet my power consumption was 13.9 kWh/100km according to the board computer, without losses. That was with summer tires. Last 2 days same temperature, but roads dry, went down to 13.0 kWh/100km, with winter tires. Difference between summer and winter tires doesn`t seem too big.

Frank

 

[MikeS]

I understand the issue with colder temperature but the range on my i3 dropped significantly before the temp dropped below 14 deg C so I don’t think BMW can blame the weather.

 

[TomMoloughney]

I understand the issue with colder temperature but the range on my i3 dropped significantly before the temp dropped below 14 deg C so I don’t think BMW can blame the weather.

My records show my EVs (MINI-E ActiveE & i3) gradually begin to lose range once the temperatures drop below 18 deg C. So by the time it drops below 14 deg C you should have definitely noticed it. By all means, have BMW look into it just to make sure there isn't any real physical problem, just don't be too surprised if they come back and say the battery is fine.

The KLE (onboard charger) that everybody will eventually have replaced ( I see in another thread that you have had it changed) doesn't have anything to do with the car's range. You don't even need the KLE, as the car has a 3.6kW inverter in the EME that will charge the car fine without the KLE, it just takes twice as long

 

[Ruffles]

I've definitely noticed the range change with the temp. Unfortunately, I bought my car the end of Nov. so I've never seen the "good" range. I'm keeping my fingers crossed that I'll be doing the happy dance in the spring when I hit 80+ miles.

 

[TomMoloughney]

I've definitely noticed the range change with the temp. Unfortunately, I bought my car the end of Nov. so I've never seen the "good" range. I'm keeping my fingers crossed that I'll be doing the happy dance in the spring when I hit 80+ miles.

Oh you will, I promise. It's just another reason to love the Spring!

 

[WoodlandHills]

It would behoove an EV buyer to plan on buying in the depths of winter: the range would be at its worst, and the buyer would be able to see if the EV was suitable for purpose in its worst case range scenario. At least there would be no Winter Surprise as there is for summertime buyers.

 

[TonyWilliams]

I use a simple rule of thumb on lithium cells that we lose 1% capacity per 2C/4F below 20C/70F, therefore a freezing temperature of 0C/30F would lose 10%, and a really cold temperature of -20C/-10F would lose 20%. Again, I'm talking about BATTERY temperature, not ambient air temperature.

This works great until you start to factor in the power consumption of the battery heater, which is going to be vastly different for every car and situation. The ONLY way to know how much power that is would be to read it off the CAN bus on the car, or measure it with your own equipment. There are just too many variables to accurately guess. The same goes for cabin heating.

So, let's say that you're the advanced EV driver, and you know that to get maximum range, you needed to preheat the cabin and battery (and you've done that), and by some stroke of luck, the battery just happens to get over 20C/70F (even though it might be -20C).

So, you are therefore starting out with ALL the available energy that the battery has to offer. If you have a heated garage, this might actually be the case. The other variables to range (not what the GOM says, but actual range... how far can the car go given a set of metrics) can be estimated.

Speed - thankfully, this is very easy to calculate.
Wind - easy to factor
Snow, Rain - you're going to have to guess
Cabin/Battery heater - another big guess
Ambient Temp - easy to factor increased air density in cold air
Winter tires - you may have snow tires that increase rolling resistance

That's really it. The bottom line is to know how much energy you start with and monitor the consumption to make sure that you're going to make it. With experience, you'll learn that the worst combination of events can cut your range in half.

Knowing what makes an electric vehicle go the FARTHEST might help to understand why it goes less in cold weather.

Longest Range Pointers

1) Drag - Wind resistance - high elevation and hot ambient temperatures thin the air, making it easier for any object to pass through the air. In the airplane business, we call this calculation "density altitude". Here's an easy to use online version: http://wahiduddin.net/calc/calc_da.htm. The most "aerodynamic" vehicle will cut through the air with the least resistance.

2) Drag - Rolling resistance - drag from everything that rotates to move the car; tires, wheel bearings, u-joints or cv-joints, gears and bearings, gear lubricant. Generally, the hotter the lubricant, the lower its resistance; the higher the tire air pressure, the lower the tire resistance.

3) Gravity and Mass equals Weight - as long as there is gravity, it will take energy to accelerate mass and energy to propel mass at speed. Obviously, it also takes significantly more power to lift the mass away from the gravitational pull while driving uphill. Quite simply, lighter is better.

4) Ideal speed - every vehicle has a speed where the intersection of the power required to overcome drag and weight is the least. Heavy cars with high drag tires (but extremely aerodynamic) like a Tesla tend to be most ideal in the 20-25mph range and small, lower mass cars like BMW i3, LEAF and Spark EV are probably in the 10-15mph range. Obviously, anything that uses power that isn't being used to overcome drag and weight is a waste; the heater, a/c, etc.

5) Hot batteries store more energy - the hotter the better, however, this same heat tends to significantly shorten their life (Nissan LEAF in Phoenix) and in some cases (Boeing 787), make the battery fail.

That's it! Hit the ideal speed, at the lowest weight with the least drag and the most stored energy!!!!

 

[GHi]

Need to do a 118 km trip tomorrow. i3 BEV, winter tyres, dry weather, no wind, 6 deg Celsius, mostly flat highway.
Should I give it a try or is it hopeless ?

 

[TomMoloughney]

Need to do a 118 km trip tomorrow. i3 BEV, winter tyres, dry weather, no wind, 6 deg Celsius, mostly flat highway.
Should I give it a try or is it hopeless ?

I would say you should be able to make it if you keep your speed down. If you see you're cutting it close, just slow down. Speed kills (range).

 

[fdl1409]

I use a simple rule of thumb on lithium cells that we lose 1% capacity per 2C/4F below 20C/70F, therefore a freezing temperature of 0C/30F would lose 10%, and a really cold temperature of -20C/-10F would lose 20%. Again, I'm talking about BATTERY temperature, not ambient air temperature.


According to the service menu the loss is less than that. In the summer months I had an average max. capacity of 19.7 kWh. Battery temperature around 20°C. The lowest I have seen so far was 19.2 kWh when battery temperature was down to +1°C. That is only 2.5% less capacity for around 20°C lower temperature. Last week after a 110 mile day with some charging in between battery temperature went up to 15°C and max. capacity 19.6 kWh again.

This works great until you start to factor in the power consumption of the battery heater, which is going to be vastly different for every car and situation.

There is no battery heating unless you have seat heating and set a timer. Have watched that closely. Started for example with 2° battery temperature, drove 11km slightly downhill and after 15 minutes the same road back slightly uphill. After 22km ( 14 miles ) battery temperature had only got up to 3°C. Certainly no active heating, and that is the information BMW confirmed.

Need to do a 118 km trip tomorrow. i3 BEV, winter tyres, dry weather, no wind, 6 deg Celsius, mostly flat highway.
Should I give it a try or is it hopeless ?


I agree, no problem if speed is not too high.

Frank

 

[mindmachine]

According to the service menu the loss is less than that. In the summer months I had an average max. capacity of 19.7 kWh. Battery temperature around 20°C. The lowest I have seen so far was 19.2 kWh when battery temperature was down to +1°C. That is only 2.5% less capacity for around 20°C lower temperature. Last week after a 110 mile day with some charging in between battery temperature went up to 15°C and max. capacity 19.6 kWh again.




While the battery capacity is showing only 2% less energy stored, what you are missing is that the colder battery will not deliver that capacity. Instead of 4.4 miles /kwh you will probably get closet to 3.8 miles/kwh. Heating the cabin and blowing air on the windshield ect... are going to be extra loads too.