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What is up with the cold and the range?

5K views 48 replies 12 participants last post by  Yinzer 
#1 ·
So I've read a few mentions about the cold and how it shortens the range on the ED. I didn't know to what effect when mentioned in other posts. All of the sudden, I'm seeing my ED tell me I only have 60 or even 55 miles on a full charge. It's doesn't seem realistic based on the amount of battery I have left on the meter. But the computer if giving me some seriously low distances.

Is what the computer is calculating real or is it speculating that I'm going to use the heater that much? It's just been in the 30s and 40s around here. I can't imagine how bad the range will get when it really gets cold. Do you guys charge a lot more during the winter months?


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#2 ·
So I've read a few mentions about the cold and how it shortens the range on the ED. I didn't know to what effect when mentioned in other posts. All of the sudden, I'm seeing my ED tell me I only have 60 or even 55 miles on a full charge. It's doesn't seem realistic based on the amount of battery I have left on the meter. But the computer if giving me some seriously low distances.

Is what the computer is calculating real or is it speculating that I'm going to use the heater that much? It's just been in the 30s and 40s around here. I can't imagine how bad the range will get when it really gets cold. Do you guys charge a lot more during the winter months?
Yeah, it's an issue with all EVs - double whammy of needing more juice for heat, defrost, headlights and the battery chemistry not being as efficient in storing and discharging energy at lower temps. With the LeafSpy app and a Bluetooth OBDII dongle on my Leaf, I can see detailed battery info. I just watched the numbers get noticeably worse as the temps have dropped and the range estimate at full charge has dropped as well. But, it did this last winter and then the numbers improved through the spring and summer. I hit my personal best of 100 miles on a charge back in early Oct before the cold arrived. The degree of the hit varies with each manufacturer's chemistry, but they all suffer.

Try to keep it garaged, preheat if you can, and use seat/steering wheel heat instead if cabin heat to maximize range if you need it. Also, make sure tires are aired up properly as the pressure drops in the cold.

And, don't forget that ICE vehicles get their worst mileage in the winter as well. :)
 
#3 ·
rfernatt, is pretty much spot on with the impact of cold weather.

Most of the temperature degradation is beyond your control but garage shelter and pre departure cabin conditioning while plugged in can help. Beyond that, heater/defroster are not your friend. If you have bun (seat) warmers when possible bundle up and use those instead of the heater.
 
#4 ·
Keep in mind that the guesstimate "range remaining" display is just that. Especially when you turn the fan on, it deducts a lot of miles purely based on outside temperature. Unless you like it toasty warm in your car, you can go a lot further than it thinks.

The heater is by far the bigger effect on range than reduced battery capacity, especially if you charge at night: the battery doesn't cool off that quickly. So if you dress according to the weather and use the heater moderately, you can enjoy the car all winter.
 
#5 ·
Thanks everyone. I sort of felt like the computer's estimate wasn't lining up with the percentage of battery I was seeing. I'm used to using about 10% of my battery on my drive to work. The computer is taking off more miles that I would normally see but my pod gauge is still only going down about that normal 10%. So I assumed the computer was adding the cold as a factor.

Still finding these cars fascinating at how they work. So much to learn.

Thanks for the tips on the seat heaters. I was thinking they were a bit of a luxury. I didn't realize they were a battery saver over the cabin heat. Now I know that it's the other way around.


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#6 ·
The smart estimates the range from past consumption data, and also adjusts it based on temperature and heater usage - you will notice a big downward jump in the estimated range when you turn the heat on.

Couple things I like to do:

1. Always reset the trip odo when fully charged - you can use this along with the SOC gauge to make your own more accurate estimate of the range than the car does.

2. You can turn the right stalk control until you get to the "reset" window on the information display (the window that shows, miles, average speed, and miles per kwh since last reset) If you reset this window (push left button on speedo panel) it also resets the memory for the range calculation and will provide more accurate range based on the current trip and conditions.
 
#7 ·
Not sure if anybody mentioned it, but the "estimated range" computation will immediately revise its estimates based on whether you just turned on the heater (or a/c) or not.

You can always go into the instrument cluster and delete its trip data so it will start with a new revision as well. Quite often, I have clients returning to the dealership to ask questions about why their "estimated range" is not > than or = to 68 miles. Usually, it's because they don't realize that all those days, weeks, months, of sitting in the car with the heat or a/c on while you're talking on your cellphone for 15 or 20 minutes prior to actually going somewhere is consuming battery energy while achieving 0 travel distance.

After a while, the computer starts estimating range that is considerably less than 68 miles or 75 miles. Reset the memory and it will start from scratch again, spitting out mileage estimates of 68 or 75 or 80 like it did when it was brand new.

But with that said, YES, absolutely YES, cold weather will have a sizeable impact on your driving range. I even see it flicker from normal to erratic estimates when it is really cold out. In my experiences, if the car has been sitting in weather below roughly 40 degrees I wouldn't trust it to go 68 miles. I might not even try 50 miles those days...
 
#8 · (Edited)
Yes, I just mentioned your suggestion in my post above yours.

...and if you think the range at 40F is bad - you should try -10F while also slipping around in the snow climbing hills..This took the range down to only about 35 miles last winter. Fortunately, such conditions only happen a couple times a year on average where I live.

But I really dont know how a Smart ED can be practical in places like northern Minnesota, Dakotas and most of Canada except for warmer areas like Southern Ontario or Vancouver.
 
#9 ·
I bought an after market seat heater kit (relay, two pads, cables, control switch) and wired it into the remaining switched option fuse position on the SAM. One pad is under the driver mat, the other is under the passenger mat. The switch is Low:Off:High and we run it at high for 5-10 minutes and then switch it to low.

Keeps the feet warm and helps heat the car. So far the seat heaters are doing the rest. Temperatures around freezing to 5C (40F).

That 4kW hair dryer they call a cabin heater is a glutton for power.
 
#12 ·
I'm in Dayton, Ohio so our temps are about the same. Good to know we're consistent.
Yeah, but at least you don't have to deal with much in the way of hills. I'm not sure how that affects range.

Based on my reports of range from several members of this forum in mostly flat Toronto (and not much colder on average than Pittsburgh) hilly terrain (assuming the trip is not a mountain grade all the way to the destination) does not seem to degrade range. Presumably descending the longer hills allows a couple miles of regen mode - which makes up for the extra energy going uphill. I know that if I am headed downhill into town my range-remaining indication will usually go up - sometimes by more miles than the drive.

Then again, there is (or used to be) a sizable faction in the home EV builder community who insist that regen has little to no benefit on range - but they mostly drive the cars in flat areas...
 
#13 ·
First thing to do is to turn OFF your heater. That is robbing you of lots of mileage.

I use my seat heaters on a daily basis and rarely turn on my cabin heater.

Next would be to reset your remaining miles indicator when you are fully recharged
(check your manual for the procedure)

In my ED, this always shows around 90 miles to "empty" after a full charge?

Then drive very cautiously and keep an eye on both the state of charge meter and the miles remaining indicator.

Hope this helps?
 
#14 ·
Sometimes you need some warm airflow to keep the windows from frosting.
But even on the first setting, the fan is way stronger than necessary, wasting a lot of precious energy (and making a racket!).

Solution: add a resistor to reduce the fan speed further. Along with a bypass switch, so I now have an additional 1/2 speed setting. Less fan noise, less heater power, and still clear view.
 
#15 ·
Sometimes you need some warm airflow to keep the windows from frosting.

But even on the first setting, the fan is way stronger than necessary, wasting a lot of precious energy (and making a racket!).



Solution: add a resistor to reduce the fan speed further. Along with a bypass switch, so I now have an additional 1/2 speed setting. Less fan noise, less heater power, and still clear view.


Wow, I have this same problem and had a similar idea. I thought about a potentiometer in line with the fan speed switch. Then I could turn it down low enough for just some air flow. I can't just run without anything because I tend to fog up the windows but I turn it on and off a lot just to save the battery. So I figured if I could just turn it down even further, I'd have a happy medium.


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#16 ·
It's the gray wire. This is in the driver side footwell next to the go pedal.
Just make sure your pot is rated for the current. Normally, the fan draws 4A in setting 1, which flows through that wire.

I found a 2.5 Ohm resistor is about right, and it's much easier to get fixed resistors with the right rating. I just happend to have two 5 Ohm, 10W resistors lying around...

 
#22 ·
#24 ·
The observed increase is becasue it is predicting usage based on ongoing consumption. If you drive more gently and use the regen effectively, or go down a long hill, the estimate range will increase because you are beating the prediction and it adjusts accordingly. I don't think a warming pack affects the reading. It does not warm by much - the smart pack cooling syatem is only needed in very hot weather.
 
#28 ·
So along the lines of this discussion, does anyone know of the pod on the dash reads an actual battery level or a calculated one? I drive 8 miles to work. When I get there, the battery level is about what it would be in warm weather but my estimated mileage is reduced way more. So it seems to me that the dash pod is reading an actual battery level and not an estimated one. Does anyone know for sure?


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#30 ·
Regarding a warming battery pack, though I think the above commenters are correct about the calculations based on how you drive, there is definite validity in a warming pack having more juice than a cold one. I made up some small LIFEPO4 packs using the "large AA size" from scratch for the various vehicles around my homestead. Complete with BMS card. The one I constructed for the ATV that I use at the airplane hangar, I made silly small, only 4P3S, that is 4 parallel, standard to make 14v, and 3 sets of them in series. In warm weather it'll start the ATV like a dozen times successfully. Now in winter it won't turn the engine over. But if I click the starter like 20 times in a row with say, 5 seconds delay in between, the battery warms up considerably, and almost magically has more than enough power to start the engine. I will likely expand the pack, but it's an interesting phenomenon with lithium cells to watch.

So it makes one wonder if there's a way to warm the pack before departing, while on the charger. At least the first leg would have normal range.

Svaraman, you're correct that the series resistor wastes some power, but it's not total loss, as the current isn't constant, pre-change, and after. There is some savings as you're greatly reducing the overall current. I ran a calc myself to check. It's still a bit wasteful but it'll save some energy. Just calculate the current based on the new total resistance, multiply it by 14v, that's the new total power. Multiply that same current squared by the new added resistor, that's the "loss" in the series resistor.
 
#31 ·
emailchrishall, I suspect you are correct. The dash pod constantly indicates a calculated current state of the battery, probably just based on pack voltage, likely has nothing to do with temp and driving conditions, much less future estimates. The in dash estimate remaining range is the one giving heartburn, it's certainly estimating based on temp, and likely recent driving efficiency thrown in for good measure. Looks that way from here, at least.
 
#33 ·
emailchrishall,

A resistor definitely used energy - why do you think they have wattage ratings along with their ohm values?

supersmartie,

The energy consumed by the blower motor is minuscule compared to the high-voltage heater element. You don't save any energy to speak of slowing the motor down, even if the resistor didn't use up the same amount of energy you re trying to save. You might overheat the heater element though.
 
#34 ·
The energy consumed by the blower motor is minuscule compared to the high-voltage heater element. You don't save any energy to speak of slowing the motor down, even if the resistor didn't use up the same amount of energy you re trying to save. You might overheat the heater element though.
You are right, the power to the fan is not my concern. But you're mistaken about the heater: The High-voltage heater is a PTC element. Effectively it has it's own temperature control (which you can't change) to prevent the burnout you are concerned about. Without that, the heater would burn out anytime somebody in Texas put the fan on low and the temp on max by mistake. MB thought of that.

Slowing down the airflow significantly reduces the power to the heater, as it maintains the same temperature of the heating element with a lot less air going across to cool it.

That's the whole point of taming the blower!
 
#35 ·
Correct me if I am wrong
1. Ohm law I=U/R
Heat law Q=I^2 × R

The more resistance we have - less current flows
Heat dissipation on fan(f):
Qf= If^2 × Rf = ( U / Rf)^2 × Rf = U^2 / Rf

Heat dissipation on fan(f)+resistor(r)
Qfr= (U /(Rf+Rr))^2 ×(Rf+Rr) = U^2 / (Rf+Rr)

Lets find out: How much more heat dissipates on fan alone compared to fan+ resistor
Qf/Qfr = ( U^2 / Rf )/ (U^2 / (Rf+Rr) ) = (Rf+Rr) / Rf = 1 + Rr/Rf
So if Rfan equals Rresistor we have two times economy in heat dissipation.

2. It seems that fan works from 12v battery that is sporadically charged from HV battery - not sure what is fan wattage - doest HV need to charge 12 V when fan works for say 2 hours or not
 
#36 ·
Supersmartie,

So basically, by keeping the element hotter (less air flow), it draws less current - and with a high positive temp coefficient maybe a lot less current? But also now you don't have enough heat to keep you warm.
Why not keep the fan on low and the thermostat on its lowest setting - periodically turning it off? On cold days, I wish it had a lower thermostat setting than 60F.

I have a little room heater with such a burn-out proof high ptc element. I will connect to a kill a watt to see what the draw at various fan settings are.
 
#38 ·
On cold days, I wish it had a lower thermostat setting than 60F.
That's basically what this mod does, only a little different:

I don't like the idea of a "room thermostat" in a car at all. I don't want the car to blow hot air until the interior matches a set temperature, and then blow cold and lukewarm intermittently to maintain the temperature.

With the mod, I can have it blow warm air continuously. No matter what the thermostat says.

Oh, and it cuts down the noise: Even on 1 the fan is the loudest thing in the whole car! On 1/2 it's barely audible.
 
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