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Discussion Starter · #1 · (Edited)
So I did pick up my hummer yesterday, but the rest of my day didn't quite go as planned. Went out early this morning before traffic picked up to get some experimentation in, so here's the data from that. I intended on doing 4 loops but didn't have enough battery to complete the 65 mph loop.

53.5 mile loop on I-75.

Speed1st leg2nd legAvg wh/miHeater cons.
801050 wh/mi1003 wh/mi1026 wh/mi1.3 kWh
75956 wh/mi890 wh/mi924 wh/mi1 kWh
70871 wh/mi785 wh/mi829 wh/mi0.80 kWh

These are all numbers derived directly out of the BECM. Quite a bit of headwind on the northward part of the trip. Temperature stayed between 27 F and 29 F the entire test. 80 mph loop was in the dark, so the heater consumption might be just a little bit swayed because of that, but really doesn't seem like by much. Started at 95% charge and ended at 21%. For the entire trip, Energy Display says 173.8 miles driven and 160 kWh consumption.

Rectangle Font Parallel Wood Paper


Some observations:
My assumption about low efficiency vehicles having less of a penalty for heating in the winter time seems to be true.

BECM estimated total battery capacity was 217.26 kWh at the start of the trip, 214.90 kWh at the end. Probably still need more miles for it to settle on actual capacity.

BECM seems to keeps track of energy recaptured during the charge cycle but I don't see it displayed on the car anywhere. The value given is 10.6 km. Not sure if that's amount of miles recovered or the amount of distance covered while under regen.

There is an actual "One Pedal Driving" mode in the settings menu, that when set to high, seemed to dramatically increase the amount of regen available. Near the end of the trip, at 55 mph, while holding down the regen paddle, I saw ~234 kW going back into the battery in "D". I didn't have time to experiment further but it felt like I practically slammed on the brakes. I'm used to one-pedal from other vehicles and this was stronger than anything I've felt before.

It seems like Supercruise drops out when the truck loses cell coverage. It dropped out in the same spot on my loop in the first and second legs. Attempting to reenable it right away apparently locked me out of using it again, not sure if it was just the rest of the drive or what. Automatic lane changes worked pretty well except for the spot where it needed a lane change around a sharp corner, it opted to slow down. When I initiated the change it didn't complete the change and ended up just driving down the middle of two lanes.
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Looks like ca. 1.1 miles/kWh in the cold on the interstate. My Bolt is showing 2.9 miles/kWh over the last week which has been in the single digits in the morning and in the teens to low 20s in the afternoon. My driving is mostly town. This time of the year shows the worst miles/kWh as one would expect. In the summer while diving the same commute I see 5.5 to 6.0 miles/kWh so you'll probably get twice the miles per kWh in the summer.
 

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So I did pick up my hummer yesterday, but the rest of my day didn't quite go as planned. Went out early this morning before traffic picked up to get some experimentation in, so here's the data from that. I intended on doing 4 loops but didn't have enough battery to complete the 65 mph loop.

53.5 mile loop on I-75.

Speed1st leg2nd legAvg wh/miHeater cons.
801050 wh/mi1003 wh/mi1026 wh/mi1.3 kWh
75956 wh/mi890 wh/mi924 wh/mi1 kWh
70871 wh/mi785 wh/mi829 wh/mi0.80 kWh

These are all numbers derived directly out of the BECM. Quite a bit of headwind on the northward part of the trip. Temperature stayed between 27 F and 29 F the entire test. 80 mph loop was in the dark, so the heater consumption might be just a little bit swayed because of that, but really doesn't seem like by much. Started at 95% charge and ended at 21%. For the entire trip, Energy Display says 173.8 miles driven and 160 kWh consumption.

View attachment 1788

Some observations:
My assumption about low efficiency vehicles having less of a penalty for heating in the winter time seems to be true.

BECM estimated total battery capacity was 217.26 kWh at the start of the trip, 214.90 kWh at the end. Probably still need more miles for it to settle on actual capacity.

BECM seems to keeps track of energy recaptured during the charge cycle but I don't see it displayed on the car anywhere. The value given is 10.6 km. Not sure if that's amount of miles recovered or the amount of distance covered while under regen.

There is an actual "One Pedal Driving" mode in the settings menu, that when set to high, seemed to dramatically increase the amount of regen available. Near the end of the trip, at 55 mph, while holding down the regen paddle, I saw ~234 kW going back into the battery in "D". I didn't have time to experiment further but it felt like I practically slammed on the brakes. I'm used to one-pedal from other vehicles and this was stronger than anything I've felt before.

It seems like Supercruise drops out when the truck loses cell coverage. It dropped out in the same spot on my loop in the first and second legs. Attempting to reenable it right away apparently locked me out of using it again, not sure if it was just the rest of the drive or what. Automatic lane changes worked pretty well except for the spot where it needed a lane change around a sharp corner, it opted to slow down. When I initiated the change it didn't complete the change and ended up just driving down the middle of two lanes.
View attachment 1787
Makes sense, you have a huge battery pack, so the percentage needed for HVAC have little impact. Hopefully you get some more nominal weather soon, so you can give us more consumption data.
 

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This is Keith. I sometimes do range/acceleration and battery pack performance-related tech articles for InsideEVs, usually with fellow ME George S Bower. First, congratulations on being among the first pioneers in GM's next great electrification adventure. I recall the excitement back in the gm-Volt forum's early day as the first Volts met their owners and we on the forum shared and discussed our discoveries. Fun times. Great to see a new generation of GM-EV owner's repeating that experience!

About your loop drive results:

  • Your battery pack appears to have been correctly conditioned for optimal driving range, maintaining its full 215 kWh capacity. I've seen recent several test drive instances in similar cold conditions where the pack was under-conditioned and temporarily lost some of its kWh capacity, adversely impacting an already reduced-range situation..
  • 27 deg. F air is very dense and significantly increases aero drag. Rolling resistance also increases at lower temperatures. It's just physics. There is no engineering around that.
  • Your Hummer appears to have a very effective heat recovery heat pump operating behind the scenes. Your average battery + cabin heating power was 1.7 kW, which was probably primarily driving the AC compressor, plus some glycol pump power. With the 27 deg. F outside air and all that glass, I estimate the average heating loss is about 6-7 kW. So your Hummer was probably being about 70% heated by the waste heat coming from the drive units and power electronics that previous non-heat pump-equipped GM EVs, like the Bolt, just had to "throw away". The balance was the compressor "heat". As a point of reference, my 2013 Volt, with much less volume or window area, uses about 3-4 kW of resistance heat at about 35 deg. F.
  • My range model for the Hummer estimates about 320 miles EPA and 70 deg. F - pretty close to the published 329 miles.
  • My range model @ 27 deg. F air temperature estimates 263 miles @ 70 mph (1.22 m/kWh) , 245 miles @ 75 mph (1.13 m/kWh), and 228 [email protected] 80 mph (1.06 m/kWh). About 20% higher than your test results. That was for dry roads. If some of the road on your loop was wet, (which I've seen in recent MI-based videos, that would increase the rolling resistance enough to get the actual efficiency levels you saw.
Anyway, my conclusion is the Hummer is likely driving pretty close to spec, actual operational conditions considered, with the delightful bonus that the HVAC appears to include an all-new high efficiency thermal management system.

I'm digging around now for additional information and evidence on this apparent new heat pump system and will keep fellow Hummerchatters and IEVs readers updated when I find more.

If any new owner finds themselves inspired to figure out how to pull the frunk and photo/video/describe the front drive, compressors, front AC coil, etc, underneath, please post what you find. We EV-gearheads would love to see 'em!
 

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Discussion Starter · #8 ·
If some of the road on your loop was wet, (which I've seen in recent MI-based videos, that would increase the rolling resistance enough to get the actual efficiency levels you saw.
Roads were completely dry. Discrepancy in energy usage is likely due to the amount of wind that morning. I don't have a way of measuring that while driving. The nice thing is the Hummer didn't really feel like it was getting pushed around much.

If any new owner finds themselves inspired to figure out how to pull the frunk and photo/video/describe the front drive, compressors, front AC coil, etc, underneath, please post what you find
The service manual has a little bit of detail about this. Take a look at Document ID 5844345. Quick synopsis is that there are two coolant loops but the BECM has control over a 4 way valve to decide if/when to mix them. It describes using the HV Battery as heat storage to warm the cabin faster, which I found interesting. Normal operation is to use the heat exchanger to provide heat to the cabin.

I'd offer to take some pictures/video here if it weren't so bloody cold outside still. Maybe this weekend when it's supposed to be a bit warmer.
 

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Discussion Starter · #9 ·
Your battery pack appears to have been correctly conditioned for optimal driving range, maintaining its full 215 kWh capacity. I've seen recent several test drive instances in similar cold conditions where the pack was under-conditioned and temporarily lost some of its kWh capacity, adversely impacting an already reduced-range situation..
Could be partly due to the fact that it hadn't completed the full charge yet, and I sat in the vehicle for ~45 minutes with it still plugged into the wall before taking off on the drive. Was getting my laptop set up for the data recording. I didn't record any numbers but I do remember at the start of this experiment, while still drawing the full 48A out of the wall, it was pulling a few kW out of the battery as well. It was back to charging before I left.
 

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Roads were completely dry. Discrepancy in energy usage is likely due to the amount of wind that morning. I don't have a way of measuring that while driving. The nice thing is the Hummer didn't really feel like it was getting pushed around much.


The service manual has a little bit of detail about this. Take a look at Document ID 5844345. Quick synopsis is that there are two coolant loops but the BECM has control over a 4 way valve to decide if/when to mix them. It describes using the HV Battery as heat storage to warm the cabin faster, which I found interesting. Normal operation is to use the heat exchanger to provide heat to the cabin.

I'd offer to take some pictures/video here if it weren't so bloody cold outside still. Maybe this weekend when it's supposed to be a bit warmer.
Thanks!

I found the owners manual, which gives a lot of interesting stuff. But not the service manual. Was there a specific website where it is accessible online? What you described with the two-loop/4-way valve controls matches one of the two GM patents I've found regarding a heat pump type system, as well as using the pack for thermal storage. Thermal energy storage is a concept that GM, Hyundai, Tesla and other OEM all are starting to implement to help balance out HVAC power issues and optimize efficiency. We've been doing large ice or water-based thermal energy storage for large facilities (chilled water for cooling, not water for solar heating) in the building HVAC industry for decades.
 

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Discussion Starter · #11 ·
Thanks!

I found the owners manual, which gives a lot of interesting stuff. But not the service manual. Was there a specific website where it is accessible online? What you described with the two-loop/4-way valve controls matches one of the two GM patents I've found regarding a heat pump type system, as well as using the pack for thermal storage. Thermal energy storage is a concept that GM, Hyundai, Tesla and other OEM all are starting to implement to help balance out HVAC power issues and optimize efficiency. We've been doing large ice or water-based thermal energy storage for large facilities (chilled water for cooling, not water for solar heating) in the building HVAC industry for decades.
I had a subscription to the online service manual stuff at acdelcotds.com. Some good illustrations as well but I think GM would not be happy about people sharing that stuff publicly.

Looks fairly straightforward to pull the frunk panel up. If you don't have someone to assist and I still have the truck this weekend, I can take a look at doing it. I think I figured out what my whistling problem is, the windshield isn't quite in the right spot.
 

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Thanks!

I found the owners manual, which gives a lot of interesting stuff. But not the service manual. Was there a specific website where it is accessible online? What you described with the two-loop/4-way valve controls matches one of the two GM patents I've found regarding a heat pump type system, as well as using the pack for thermal storage. Thermal energy storage is a concept that GM, Hyundai, Tesla and other OEM all are starting to implement to help balance out HVAC power issues and optimize efficiency. We've been doing large ice or water-based thermal energy storage for large facilities (chilled water for cooling, not water for solar heating) in the building HVAC industry for decades.
Oh, and the wind. I just saw that response from you. Iif you do an out/back route and have head wind one way and tailwind the other, they about balance out for net total aero drag losses, but crosswinds are an issue. They increase drag in both directions. An SAE aero research paper showed 10 miles per hour of crosswind can increase aero drag by 10-20% at 70 mph traveling speed. When I plug in an adjustment for 15% aero drag increase, it brought the 80 mph range down to 212 miles, which is very close to your actual Wh/mile.
 

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I had a subscription to the online service manual stuff at acdelcotds.com. Some good illustrations as well but I think GM would not be happy about people sharing that stuff publicly.

Looks fairly straightforward to pull the frunk panel up. If you don't have someone to assist and I still have the truck this weekend, I can take a look at doing it. I think I figured out what my whistling problem is, the windshield isn't quite in the right spot.
Hmmmm..... Please keep us posted on the windshield. Is it not seated right?
 

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Discussion Starter · #14 ·
Oh, and the wind. I just saw that response from you. Iif you do an out/back route and have head wind one way and tailwind the other, they about balance out for net total aero drag losses, but crosswinds are an issue. They increase drag in both directions. An SAE aero research paper showed 10 miles per hour of crosswind can increase aero drag by 10-20% at 70 mph traveling speed. When I plug in an adjustment for 15% aero drag increase, it brought the 80 mph range down to 212 miles, which is very close to your actual Wh/mile.
This is what my route was, kind of hilly and not really a straight shot. Started on the southern end.
Ecoregion Map World Line Parallel
 

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Wow. I expected low efficiency, but wow. I am a new EV owner, a Ford Mustang Mach-E, and I have been getting around 2.4 mi/kWh on the highway at 75-80 mph speeds. I would love to put that 200 kWh battery in my car! Want to trade batteries?
 

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Wow. I expected low efficiency, but wow. I am a new EV owner, a Ford Mustang Mach-E, and I have been getting around 2.4 mi/kWh on the highway at 75-80 mph speeds. I would love to put that 200 kWh battery in my car! Want to trade batteries?
Your Mach E seems really bad, what climate are you in? I just did a 300+ mile round trip Phoenix to Tucson driving 70-75 and got 3.5mile/kWh. Last summer driving up a 6000ft elevation change at 75 mph I got 3.1mile/kWh. I have the CA Route 1.
 

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Your Mach E seems really bad, what climate are you in? I just did a 300+ mile round trip Phoenix to Tucson driving 70-75 and got 3.5mile/kWh. Last summer driving up a 6000ft elevation change at 75 mph I got 3.1mile/kWh. I have the CA Route 1.
I have the GT model, so definitely your efficiency will be better. My car's EPA range is 270 compared to yours at 300. 2.4 mi/kWh equates to a highway range of 211 miles, which is about what is expected especially in winter. In the summer I am sure it will be better, maybe 2.6-2.8 on the highway, but I don't expect high efficiency driving at around 80 mph.

If I slow down to 70, the efficiency will go up measurably. Same for warmer weather - anything above 60-70 F makes a big difference.

Since this is a Hummer forum, the same applies to the Hummer. At 70 mph, the Hummer will do much better than at 80 mph, exactly at @Dark-Fx demonstrated. And winter temperatures kill battery performance for all EVs.
 
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