Range of 66 miles, in seriously cold weather (no cabin heat)

[Arthur]

Today, I drove from Corning, NY to Ithaca, NY, and back to Corning. The average temperature, for the round-trip, was probably around 10 deg F.

Given that the one-way distance is just under 45 miles, my battery never quite dropped below the 1/4 mark. (I was able to charge back up to full, while in Ithaca.) The trip has a number of steep hills, which, from my experience do not affect range significantly, unless do a lot of hills, when the battery really isn't warmed up, yet. Corning is at a higher elevation than Ithaca, and my house, on a hill outside of Corning, is even higher. However, the average slope for one way is about 25 ft per mile, and the effects of the slope cancel out, for the round-trip.

Since I wanted to see what the best possible range would be, in weather this cold, and since I wasn't sure what it would be and didn't want to get stranded in the middle of nowhere, on a cold winter night, I put on my Arctic-quality parka and my best sheep-skin mittens. Then, I completely shut off the cabin heat, but cranked up the seat heater to "4." My nose, toes, and fingers were seriously cold, by the time I got home. It felt really good to stand in front of the roaring fire, in our wood stove.

I mostly kept my highway speed (the majority of the trip was highway) between 45 and 55, probably averaging a little over 50 mph.

Anyway, averaging for the round-trip and projecting out to what I would have gotten, if I had run the battery down to empty (which would be a seriously insane thing to do, on a night like this) I figured that my range on terrain with no net slope would have been about 66 miles. On the uphill half of the trip, it would have been about 61 miles, with 71 miles on the downhill half. Again, that's with seat heater at 4, NO cabin heat, 10 deg F outside temp, modest driving speeds, and assuming that I ran the car until the battery was very close to dead.

It's a fairly decent result, I would say, but, now I'm going to have to figure out how much heat I can get away with, so I can be a little more comfortable, but still not risk running my battery down to zero charge.

One disturbing thing I noticed was that my calculations were showing (based on the fact that I had just over 1/4 of a charge left, when I got home, and that my car said 28% SOC, and that MyFordMobile was showing an energy use, for the return trip, of 12.9 kWh) my usable battery capacity to be no more than 18 kWh. I don't know if that's some kind of effect of winter driving or if my battery has degraded that much since I bought the car in February 2013. Maybe there's just some inaccuracy or inconsistency in the numbers I'm getting.

 

[Richmond72]

I think those are good results for the cold. Did you preheat the cabin in either direction?

 

[sefs]

When the battery is cold you will not get the 19.5 kWh expected in temperate climates. I typically get 15.5 to 16 kWh in sub freezing temperatures. However, when the temperature warms back up, I get the 19.5 kWh again.

Did you have to leave your windows cracked to prevent fogging? That's what I've had to do when turning the heat off to extend range.

 

[v_traveller]

Would heated socks and gloves help? Not sure what to do about the nose, besides wear a mask... you are a brave one!

 

[Arthur]

Thanks for your feedback on what I wrote.

Yes, I did pre-heat the cabin a little, but just by doing a remote start with my key fob. I didn't set a go time. I just did a 10 minute remote start warm-up, once or twice, while I was still plugged into a 240v charging station (at both home and destination). So, it didn't affect my total amount of starting charge.

In terms of fogging of windows, I did NOT roll down the windows. It seemed like I was just starting to get a little fogging, by the end of my 45 mile (1 hour) trip. I did NOT put it on recirc. I turned off all of the options on the heating/cooling system, but the fan doesn't let you set it to zero. So, I believe there was still a minimal amount of cold air coming in. I shut the dashboard vents on the driver side, so that there wouldn't be air blowing directly on me, which is why I probably got a trace of fogging on the driver side, but it wasn't enough to hamper visibility.

Yeah, from my calculations, it seems like my max allowed charge capacity had dropped down to about 17.8 or 17.9 kWh.

If I assume a loss of 20 miles of range, due to cold weather (from 86 miles in warm weather, to 66 in cold), which is my best estimate of what result I would have gotten at similar driving speeds, in summer, ...my calculations show that I probably lost 14 of those 20 miles from energy going to run the system that heats the battery. The remaining 6 miles lost, would be from the battery capacity drop, from 19.5 kWh, to about 18.

My only remaining question is: Is this limiting of battery capacity a planned function in the software (in response to detected temp), or is it purely a result of reaching some electrical criteria (rate of current flow, into or out of the battery?) earlier, because of the effect temperature had on that criteria?

...and yes, I will definitely have to look into heated socks and gloves. That would have been all I needed. My wife has knitted me a nice wool "balaclava" that covers my nose, but I couldn't find it.

Perhaps I can ask her to design and knit me an integrated set of socks, mittens, and balaclava, with heating elements woven into the critical parts of each, and the power cords carefully integrated, so that I would have a single plug that I could plug into the car, while driving (no batteries involved). That way, I would be able to be sure that the energy drain was not significantly affecting my range. Hah! Am I THAT crazy?!?! Probably.

 

[sefs]

The limit of the battery through the software is based on state of charge (voltage). The energy you can get out of that state of charge window is less when the temperature is colder. Thus, you get less kWh out of the battery. The limits are not changed based on temperature, as far as I know.

 

[v_traveller]

My only remaining question is: Is this limiting of battery capacity a planned function in the software (in response to detected temp), or is it purely a result of reaching some electrical criteria (rate of current flow, into or out of the battery?) earlier, because of the effect temperature had on that criteria?

Good question... I've been trying to look up info online, but even batteryuniversity.com doesn't have a clear answer.

Found this on wikipedia:
http://en.wikipedia.org/wiki/Lithium-ion_battery

"Consumer-grade lithium-ion batteries cannot be charged at temperatures below 0 °C (32 °F). Although the pack appears to be charging normally, permanent plating of metallic lithium can occur on the anode during a subfreezing charge, and cannot be removed with cycling...."

".... Most devices equipped with Li-ion batteries do not allow charging outside of 0-45 °C for safety reasons, except for mobile phones that allow some degree of charging when they detect an emergency call in progress.[54]"

So based on that, I suspect that the battery management software does respond to temperature; if the battery pack is under 32F I'm guessing that regen is disallowed, therefore reducing predicted range, until the thermal mgmt system elevates the battery pack temp to above freezing. But the thermal mgmt continues to heat the battery, presumably until it's at 60-65F, which also has an adverse effect on predicted range.

Just my guess based on limited info I was able to find... anyone else able to dig out some published info on this?

 

[Gigi]

My only remaining question is: Is this limiting of battery capacity a planned function in the software (in response to detected temp), or is it purely a result of reaching some electrical criteria (rate of current flow, into or out of the battery?) earlier, because of the effect temperature had on that criteria?

I think that the change in battery capacity you are experiencing is something that is happening on the molecular level in the battery itself because of the cold, not something that happens at the level of software controlling the battery.

Think of the difference in how fast a regular 12V battery cranks the engine to start an ICE car in the summertime versus how slowly it cranks the engine when the temperature is in the single digits. The difference is not only that the engine oil has gotten thicker because of the cold; the battery itself has less fewer Amps of cranking power available because, in the cold, its molecules move more slowly and produce less cranking power. In the same way, the FFE's battery has less kWh capacity because the lithium ions move more slowly from one electrode to the other in the battery when it is cold and more of their energy is wasted in the process.

I'm not a physicist or an engineer, so this is my layman's understanding of what's going on. Someone with more expertise is welcome to straighten me out if there is something in the above that isn't correct.

 

[Arthur]

I'm guessing that the explanation for the range loss, at very cold temperatures, is somewhat more complicated. If the battery temperature was being maintained (during driving) at, for example, 40 deg F, then we would not see any more of a loss in our total battery capacity, at outside temperatures of 10 deg F, than we would at outside temperatures of 40 deg F. The fact that we DO see a reduced capacity (kWh) at 10 deg F, tells me that they are either trying to balance multiple factors, like cold-weather range and total battery lifetime (perhaps by maintaining an internal battery temperature of 25 deg F, when the outside temperature is 10 deg F), or maybe they really are messing with the maximum and/or minimum allowed state of charge.

Another thing to think about is that the FFE (LG Chem) battery cells use a Lithium Nickel Manganese Cobalt Oxide (NMC) chemistry. This is the same chemistry as the LG Chem cells, used in the Chevy Volt, but the Volt cells have a capacity of 15 mAh, each (with a total of 288 cells, arranged in three series circuits of 96 cells, each, with those three series circuits then placed in parallel with each other), and are 5-inch by 7-inch flat pouches. The FFE battery uses a single series circuit of 98 cells that are each 60 mAh (4 times the capacity of each Volt cell). So, that hump, in the trunk of the FFE is a single row of flat, rectangular pouch cells, presumably somewhat bigger than 5 x 7, but possibly somewhat thicker, as well, all lined up parallel to each other, like folders in a file cabinet drawer.

Most of that info has very little to do with the temperature discussion, in the first paragraph, except, perhaps, for the part about the battery chemistry. One of the most likely explanations for the reduced capacity (kWh) in very cold weather, is that the preset SOC limits correspond to certain fixed percentages of the total range of the State of Charge. If the whole range of SOC (which, in absolute terms, could be measured in Coulombs of charge) is shrunken (fewer Coulombs of charge moved from anode to cathode or vice versa) at lower temperatures, that is because the reaction does not proceed as far, in either extreme, at lower temperatures. In other words, the "fully charged" equilibrium point and the "fully discharged" equilibrium point, are both a smaller number of Coulombs of charge (transferred from one plate to the other) than they would be at a higher temperature.

So, I don't think the reduced rate of flow of charge has any effect on energy efficiency or maximum battery capacity. Slower reactions, and, thus reduced charge flow rates (at lower temperatures), would only affect the battery CURRENT and, thus, your motor's POWER output. So, it might explain sluggish performance in cold weather, but it wouldn't explain reduced range.

One thing that I can tell you is that the Nanophosphate (Lithium Iron Phosphate) EXT battery chemistry (http://www.a123systems.com/lithium-ion-battery-technology.htm), used in the Chevy Spark EV, among others (Scroll to bottom of page, for full list: http://www.a123systems.com/solutions-transportation-passenger-vehicles.htm), is MUCH less affected by temperature extremes AND much less prone to shortened lifespan when allowed to charge or discharge to extremes of SOC. In other words, it can get away with much less thermal management and much less restriction of SOC limits.

I know this, because I had the original Nanophosphate chemistry, in the Hymotion/A123 plug-in hybrid conversion, that I had had installed in the 2008 Prius that I had, before I got my FFE. It started out with about 4.7 kWh of battery capacity and is still working, over 5 years later, with a battery capacity that is still over 4 kWh, ...and it'll give you that full 4 kWh, in summer or winter. It just takes longer to use it in winter, because the Prius's Nickel-Metal-Hydride battery is so sluggish, in cold weather.

Unfortunately, the Spark EV is too much of a tiny "city car," with baby-sized, rear-wheel-drive tires, for my uphill gravel/dirt driveway, in the NY state winters. Besides, I think it's still only available on the west coast.

 

[cta4762]

Today I reluctantly parked my FFE until March. The cold weather has too much impact on range, and I'm not willing to drive without heat. I get a cold too easily.

I live in PA. I really like my FFE from spring - fall. It's such a great car to drive.

I want another EV when my lease is up in June 2016, but it will need more battery and preferably a heat pump. And high-speed charging. Level 2 doesn't cut it for traveling. My options might be the Model 3; GM's 200-mile EV that they say will be on the market in 2017; and a hoped-for CUV based on the Volt. I prefer an EV, but if a Volt CUV goes 50 miles in electric mode (I'm guessing the # will be lower, if there is such a thing as a Volt CUV at all), maybe that's good enough.

 

[jmueller065]

Today I reluctantly parked my FFE until March. The cold weather has too much impact on range, and I'm not willing to drive without heat. I get a cold too easily.

Have you tried the 12V electric blanket? I hear from people that use it that between the blanket and the seat heat they are sweating... They can't use it when temps aren't cold enough (like "freezing" isn't cold enough).
http://www.amazon.com/Roadpro-12-Volt-Fleece-Heated-Blanket/dp/B0009Y2CFS/ref=sr_1_2?ie=UTF8&qid=1417637940&sr=8-2&keywords=12v+electric+blanket

 

[michael]

I got this one

http://www.amazon.com/gp/product/B0000DYVN9/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

for a friend. She's very happy with it.

 

[unplugged]

"I'm not willing to drive without heat. I get a cold too easily."

It is a myth that being cold causes colds.
http://www.everydayhealth.com/cold-and-flu/colds-and-the-weather.aspx
http://www.cnn.com/2014/01/07/health/upwave-colds/