GM Volt Forum banner

1 - 20 of 32 Posts

·
Registered
Joined
·
1,315 Posts
Discussion Starter #1
Now that the cold season is here and the range of EV's are getting shorter, what are the causes?

1. The battery pack could not take in more charge? If so, what would be the available kWH per full charge at low temperature, take 40F as an example.

2. Does it consume the same amount of energy from the wall for a full charge? What is the energy spent to keep batteries at optimum temperature while plugged in, let's say at 40F?

3. Does GM's algorithm play with the actual state of charge values so that the car can buffer or attenuate the effect of temperature?

4. Does the car consume more power to move it when the ambient temperature is lower? Assuming you're not spending any energy for cabin climate controls. I've noticed that it requires more kW power to maintain the car at 60 mph when temperature is lower.

5. other factors related to temperature?

I've used data from various Volt owners and analyzed them, but forgot to take data from the actual kWh used.

VoltTemp by Joe Real, on Flickr
 

·
Super Moderator
Joined
·
6,312 Posts

·
Registered
Joined
·
3,440 Posts
I suspect the main causes are
1) Heating the cabin
2) Heating the battery pack
3) Cold air is more dense, thus more aerodynamic drag. This effect also lowers tire pressures, so if you have neglected adjusting them, you will get less range due to that.
 

·
Registered
Joined
·
4,803 Posts
If the Volt is plugged in the temperature management system will maintain the battery temperature so it never drops below 32F. When charging the battery will be maintained at 40F or warmer temperature (not to exceed 90 - 95F in warm weather.)

My experience with winter driving in my 2017 Volt is that up up 25% of the EV range can be lost to cold temperatures, this is before factoring any use of the electric heat. The heated seats and steering wheel use very little power (~200 watts total) so I don't consider these accessories to be a significant power draw. I have never experienced the Volt's battery heater use more than 1 - 2 % of the battery charge while driving. A major reason for the reduced range is that the chemical reaction within the battery that enables electrons to flow is less efficient at lower temperatures. The battery functions much more efficiently at 80F than at 32F.
 

·
Registered
Joined
·
3,252 Posts
Higher friction is one source. This includes rolling resistance in the wheels themselves. Cold air is denser so high speeds are impacted more. Batteries, including LiOn, don't like the cold and you can't get as much energy out of them. Finally, with the Volt, the hair dryer based cabin heater consumes a lot of power.
 

·
Registered
Joined
·
1,315 Posts
Discussion Starter #7
... Batteries, including LiOn, don't like the cold and you can't get as much energy out of them.
And this really made me curious.

Does the Li battery store less energy because of low temperature?
Or does it give off less energy?
Or both?
 

·
Registered
Joined
·
3,252 Posts
And this really made me curious.

Does the Li battery store less energy because of low temperature?
Or does it give off less energy?
Or both?
Batteries are chemical reactions. It takes energy to "reset" the reaction and you reset to the same point regardless of temperature. The difference is how much excess energy is created by the reaction during driving.
 

·
Registered
Joined
·
1,315 Posts
Discussion Starter #9
Batteries are chemical reactions. It takes energy to "reset" the reaction and you reset to the same point regardless of temperature. The difference is how much excess energy is created by the reaction during driving.
The Volt's battery pack is thermally managed, so I don't think that it is related to chemical reactions in the battery. I think the battery thermal management would require more power at lower temperature and is a good chunk of the consumption.
 

·
Registered
Joined
·
4,803 Posts
The Volt's battery pack is thermally managed, so I don't think that it is related to chemical reactions in the battery. I think the battery thermal management would require more power at lower temperature and is a good chunk of the consumption.
It's not. Only 1-2% shows as Other on the Energy Summary screen. This is for heating/cooling the battery.
 

·
Registered
Joined
·
6 Posts
Not sure if this comment belongs in this thread .. but .. my 2016 ELR, fully charged, only indicates a 33-35 range AFTER fully charged.
Of course, it has gotten colder outside thus why I've posted this here but the car is inside a "warm" garage.
I've recently changed my charger from the OEM 110V to a 220V Zencar. Maybe this is a factor. Disappointed as I expected 36-38 miles on electric alone (to and from work!)
 

·
Registered
Joined
·
4,803 Posts
what were the conditions? Temperature, miles driven, driving profile...
I did not record the conditions, just typical mid-Atlantic winter conditions. If the Volt is left plugged in the battery temperature management system will keep the battery temperature from dropping below 32F. While driving it takes very little energy to keep the Volt's 450 lb. battery from dropping below 32F as the battery has a large thermal mass. The battery packaging and housing provides some insulation. If you are at the arctic circle then the Volt will use more energy to maintain proper battery temperature, everywhere else I would expect the Volt to use less than 5% of the battery to maintain the battery within an acceptable temperature range, typically 1 - 2%. If anyone has any better data I'd like to see it.
 

·
Registered
Joined
·
149 Posts
Not sure if this comment belongs in this thread .. but .. my 2016 ELR, fully charged, only indicates a 33-35 range AFTER fully charged.
Of course, it has gotten colder outside thus why I've posted this here but the car is inside a "warm" garage.
I've recently changed my charger from the OEM 110V to a 220V Zencar. Maybe this is a factor. Disappointed as I expected 36-38 miles on electric alone (to and from work!)
Not to hijack a thread, but I get the same in my 2013 Volt. It's just due to denser air and greater electrical loads through heating. What works best for me and gives the most range is to preheat the car once about 20 minutes before I leave. While preheating, the car can use around 6 kw to heat the interior and battery up, while the onboard charger can only supply 3 kw, so you're at a net loss. By preheating for 10 minutes, then letting it rest for 10 minutes on the charger prior to departing, your battery will be up to temperature and nearly full again. If push comes to shove, you also have a gas-powered heater on board that makes a little electricity as a byproduct.
 

·
Moderator
Joined
·
8,680 Posts
Now that the cold season is here and the range of EV's are getting shorter, what are the causes?

1. The battery pack could not take in more charge? If so, what would be the available kWH per full charge at low temperature, take 40F as an example.

2. Does it consume the same amount of energy from the wall for a full charge? What is the energy spent to keep batteries at optimum temperature while plugged in, let's say at 40F?

3. Does GM's algorithm play with the actual state of charge values so that the car can buffer or attenuate the effect of temperature?

4. Does the car consume more power to move it when the ambient temperature is lower? Assuming you're not spending any energy for cabin climate controls. I've noticed that it requires more kW power to maintain the car at 60 mph when temperature is lower.

5. other factors related to temperature?

I've used data from various Volt owners and analyzed them, but forgot to take data from the actual kWh used.

VoltTemp by Joe Real, on Flickr
1. Technically the battery has the same amount of charge - but the internal chemical reactions become less efficient, so it can't deliver as much of the charge to the drive inverters. Here's a nice scholarly paper I think I mostly understand on the subject:

http://jes.ecsdl.org/content/165/3/A674.full

You'll note in figure 5 that at -10C the energy delivery is about 6% less than at room temperature (25C). GM thermally manages the pack for safety, but they don't hold it at room temperature in all environments (which would eat a lot of power unless they added a bunch more insulation.)

2. I don't have numbers handy for energy spent to warm the pack, either during charging or during operation. The car does warm the pack in cold weather in both environments. Pack temperatures below ~30F are dangerous for charging due to the risk of electroplating lithium metal onto the anode, permanently damaging the cell (GM ensures this won't happen - which is why there's a deeper ERDTT mode that pretty much locks the battery out in extreme cold.)

3. I haven't seen evidence of GM messing with buffers based on temperature change.

4. Aside from HVAC, loads are a lot higher at lower temperature. That same 25C to -10C drop (77F to 14F) from the battery above? That's a 10% decrease in absolute temperature. From ideal gas law (PV=nRT) with a basically constant pressure from gravity, that means the air is 11% denser, producing 11% more drag on objects moving through it. But that's not all.

The drive motors and gears are lubricated and cooled by Dexron VI ATF. I don't have a viscosity chart handy for that, but here's a generic one:

https://wiki.anton-paar.com/en/automatic-transmission-fluid-atf/

As you can see, viscosity shoots up as temperatures drop, which means more energy wasted just turning the gears.

5. HVAC. It wasn't part of 4. as you wrote it, but it's the biggest factor. Heating the cabin is expensive, and that's a big difference from the ICE world where engine waste heat is used. Because EVs are so efficient in the drivetrain, they aren't constantly throwing 20 or 30 kW of heat out into the atmosphere, so they don't have that "free" heat to draw on for the cabin. You can reduce the impact by using the heated seats more and setting the temperature and fan speed lower (but at least out here, you can't get away with turning the electric heat off - the windows will fog up pretty quickly.)
 

·
Registered
Joined
·
4 Posts
My dash shows 17 to 20 percent of my energy is going to environmental controls during the winter. That takes me from 53 to 55 miles down to 43 to 45 miles pretty quickly. Still enough for my daily commute!
 

·
Registered
Joined
·
2 Posts
I don’t think the shorter range is caused by anything other than the cabin heater. My reasoning is as follows:
1) during the summer months, when I’m driving easy, I am able to get approx. 105KM (65Miles) on a charge. This is at temps of 25 - 30 deg Celsius. (77 - 86 deg F)
2) a few weeks ago, while driving the same route using the same driving style, I was able to get 101KM (63 Miles) on a charge. This was a sunny day and the temp was approx. -3 deg Celsius (27 deg F). I left the heating system powered off. (It was fully powered off, not on with no lights on “max” or “econo” as I’ve found the heater still kicks in for some reason 🤔)
3) the same trip with the cabin heat on (I didn’t have a jacket), on a similar day, and my range was only 70 Km (43 Miles).

Just my $0.02
 

·
Registered
Joined
·
292 Posts
Energy usage by the hvac is not the only difference. That is a big contributor, but on my Bolt I use 10-20% of my energy for hvac, yet my range is 30-40% less in really cold. I know on the Volt I can see a change in reported capacity of .1-.3kwh when it’s cold. Full battery capacity when warm is 14.1, when it’s cold it’s in the high 13’s.
I do know internal resistance of the packs change with temperature, so the packs are less efficient when cold ie more voltage sag. On my drive home my usage in summer averages 3m/kWh, in winter it’s 2m/kWh or lower. IMHO this could be one of the biggest obstacles for ev’s to overcome for general acceptance. Barely being able to go 100 miles at highway speed in a Bolt in 0 deg weather is a huge difference from the summer range of 180-190 miles.
 
1 - 20 of 32 Posts
Top