[UncleDon]

2018 Volt LT 97,000 miles.

Just FYI:

I am on a cross country trip through the rockies, much of it off interstates. This is my first time mountain driving in a Volt though I am an experienced mountain driver. I started in Wisconsin. Here are a few things I observed.

I drove up a 6% incline at 70mph for 2.5 miles in Normal Mode and the battery indicated miles dropped from 37 to 16 miles in that distance. Those indicated battery miles ticked down remarkably quickly. I was wondering how hot the electric motors must have gotten drawing all that power.

I drove up another 6% incline of 3 miles in Hold Mode (16 battery miles left). Nearing the top the engine seemed like it was screaming at a very high rpm. The coolant temp was 217 degrees at the top. The car made it with no apparent reduction in performance, but I think I was at the edge of what that car is capable of. I understand physics pretty well and that engine had to be working pretty hard to lift all that weight at that speed. The battery charges nicely downhill. During the subsequent descent the battery mileage increased to 29 miles, but I don't know how far it was.

Those were the only 2 notable up slopes on this trip so far (Santa Fe to Phoenix), but the next mountain driving leg will be up towards Flagstaff then Moab UT. I will use Mountain Mode for the remainder of the trip in mountainess areas. I am be curious to see how well it works. I am also curious to see what the battery charge level (miles left indicated) will be on the "other side" if I start mountain mode with a near full battery of about 40 miles indicated. Will it return to 40 after each descent?

Downhill driving is a breeze in Low. I'm don't think I engaged the physical brakes at all. I'm pretty sure all of the downhill speed control was done via regen. But I don't know for sure.

Interesting trip. 9 days left of 15. After Moab, it's Rock Springs WY then Denver. Another learning experience.

 

[TYmrLutz]

Now you know why the Volt engineers called it "Mountain" mode! The Volt was made to go anywhere. anytime. BEVs still can't do that. Enjoy those roads less traveled, UncleDon, hope you have fair weather.

 

[wssix99]

I was wondering how hot the electric motors must have gotten drawing all that power.

The motors are designed with cooling and designed to go up mountains. I expect that they would get hotter driving on a flat road through the desert.

Nearing the top the engine seemed like it was screaming at a very high rpm. The coolant temp was 217 degrees at the top. The car made it with no apparent reduction in performance, but I think I was at the edge of what that car is capable of.

Remember that the Volt doesn't work like a normal car and the engine/generator is not attached to the wheels. The generator is optimized for running at a high RPM - much higher than a regular ICE car. The high RPM doesn't have a direct correlation to how hard a regular ICE car would work in the same situation. Its specific to the Volt and why you get much better mileage going up the mountain than an ICE car - even when you aren't using your battery.

Will it return to 40 after each descent?

The estimate should go closer to normal as you come back down, but you could see it spike really high as the computer "sees" efficient running. I expect the Guess-O-Meter (GOM) will not give you a good estimate until you hit a level stretch of road and you run for a while like that.

 

[MikeBCo]

I was wondering how hot the electric motors must have gotten drawing all that power.

Electrical motors are typically very efficient. If you were using 80 kW to climb the pass, only a small percentage was lost to heat. A comparable car needing to generate 100 hP to climb the same hill would be generating nearly 200hP in thermal losses.

I don't suspect the motors (inside the transmission) were overly hot...

 

[flyingsherpa]

Electrical motors are typically very efficient. If you were using 80 kW to climb the pass, only a small percentage was lost to heat. A comparable car needing to generate 100 hP to climb the same hill would be generating nearly 200hP in thermal losses.

I don't suspect the motors (inside the transmission) were overly hot...

Even 90% efficient motors would have to deal with 8-10kW of sustained heat here, which is not nothing. But the transaxle has its own cooling loop / radiator, and is designed for this operation, so yes I'm sure the temperature was fine.

 

[spaycace]

I have made many trips through mountain ranges (I live in Colorado) and I would recommend using hold mode while climbing in elevation. When you get to the top, switch to normal mode and let the car regen on the way down, leaving cruise control set and transmission in normal drive, not L. On a trip from my home to Las Vegas, NV, even though I used hold mode instead of mountain mode, some EV range was depleted, but easily recovered on the downhill runs. I simply kept the car in hold mode until the car was using 5kwh or less, then I’d switch to normal mode, and cycled that way the whole trip. Mountain mode in Gen 2 is not as effective as it was in Gen 1. Gen 2 saves roughly 20%, but isn’t as efficient at keeping up the 20% level. Gen 1 saved 50% and was far more effective at keeping the 50% stored for mountain driving. Anyway, I plugged in at my hotel in Vegas, and had 85 miles of EV range in the morning when I left to head for California. I was only able to get 58 miles of EV driving from the 85 projected miles, but I was also driving 80 mph for parts of the EV trip.

 

[obermd]

Here's the writeup I did on my experiences with not needing Mountain Mode.

Mountain Mode not needed (Gen 2)

It's leaf peeping season in Colorado, so this morning I filled my tank and headed for the mountains. I live at 5,700 ft above sea level and ran out of battery after a little over 47 miles and a net climb of 2,800 ft. I stayed in Normal mode the entire loop, driving over Kenosha Pass at 10,000...

www.gm-volt.com

 

[BarryD]

Remember that the Volt doesn't work like a normal car and the engine/generator is not attached to the wheels.

This isn’t really true, especially on a gen-2. The ICE is quite often mechanically driving the wheels, in addition to producing electricity.
Barry

 

[obermd]

This isn’t really true, especially on a gen-2. The ICE is quite often mechanically driving the wheels, in addition to producing electricity.
Barry

Even the Gen 1 Volt has a mode where the ICE is directly connected to the drive shaft. It's not used nearly as often as in the Gen 2, but thermodynamics is very clear - when burning gas, use what is needed to propel the car and only convert the rest to electricity. Thermodynamics is very clear that you will have a loss during the conversion to electricity.

 

[hellsop]

Can we agree to set aside the "directly connected to the wheels" argument as being too nuanced to explain to people that aren't deeeeeeply involved and settle for "The Volt always needs and uses the battery for normal operation, even while running the engine"? The places where that might not be exactly 100% pure technically true just don't matter to people wondering why they can't drive their car anymore.

 

[rrrroos]

Even the Gen 1 Volt has a mode where the ICE is directly connected to the drive shaft. It's not used nearly as often as in the Gen 2, but thermodynamics is very clear - when burning gas, use what is needed to propel the car and only convert the rest to electricity. Thermodynamics is very clear that you will have a loss during the conversion to electricity.

I have a 2017 Volt. I have the MyGreenVolt app. Today I was driving the Interstate on Cruise at 70MPH on ICE power (Hold mode). I had the MyGreenVolt app RPM / tachometer Dashboard gauge showing me ICE RPMs I don't believe there was direct connection of Ice to wheels because the ICE RPMs were constantly fluctuating depending on the grade of the Interstate.

 

[obermd]

I have a 2017 Volt. I have the MyGreenVolt app. Today I was driving the Interstate on Cruise at 70MPH on ICE power (Hold mode). I had the MyGreenVolt app RPM / tachometer Dashboard gauge showing me ICE RPMs I don't believe there was direct connection of Ice to wheels because the ICE RPMs were constantly fluctuating depending on the grade of the Interstate.

Don't forget the ICE is also used to maintain the battery buffer when in Hold mode. As such, RPM fluctuations are normal as the car determines the amount of power needed to maintain this buffer. Remember, no road is flat, so the down hills will require lower RPM to maintain the same speed (it's not a manual transmission) and the uphills will require a higher RPM. The Volt's planetary gear set is a transmission and the ICE and both electric motors all connect to it. In the gen 2 Volt more of the power from the ICE is directly transmitted to the drive shaft from this transmission.

 

[zeldar]

My experience with Mountain Mode is that it keeps (or generates) a small percentage of battery available to supplement the ICE when going up hills. If you have exhausted the battery and then turn on Mountain Mode, something I do often, the ICE will generate extra power to charge the battery to provide that supplementation when needed. In cases where I have arrived at my destination still in Mountain Mode and shut off the car, then drive it again in Normal mode (without charging), there is about 5-10% battery available that is left after using Mountain Mode. If you keep it in Normal mode, the Volt will use up that 5-10% and then switch over to the ICE. It's a great feature. I have blasted up steep mountain pass grades with plenty of power thanks to MM. Just one of many reasons I love my Volt!