Towing with the Gravity

[Dr K]

[This was also posted on Reddit -- sorry if it looks familiar...]
I specifically chose the Gravity for range and hopefully towing range, and today I got to test it out. It did not disappoint. My GGT has 7-passenger and 21" wheels so a bit of a hit on range (not what I originally ordered), and my tow was from the Maryland suburbs of DC down to VIR in Alton, VA. I was towing a sports car on an open aluminum trailer, total weight 3500 lbs with another 500 lbs of "stuff" in the car. I removed the overhead tire rack and the 8 extra wheels/tires were among that "stuff" inside the cavernous interior of the GGT.

I had done one prior 83-mile tow and watched the miles/kWh gradually increase but started quite low at 1.05. Today it started at 1.17 and climbed gradually but consistently ending at 1.40 after 250 miles, and still rising.

The first leg was almost all Interstate with some traffic. 133 miles, battery went from 99% to 31% (81.6 kWh) - 1.63 miles/kWh. That would allow an initial pull of 176 miles. But I'll be more conservative until I have more experience - see below.

For my second leg (after a quick charge from 31->92% at a 360 kW charger over about 22 minutes while I had a snack), I went 110 very hilly miles on 64% (76.8 kW), or 1.43 miles/kWh. So conservatively an initial pull would be 171 miles, and subsequent pulls (charging to 80% and trying to charge again at 10%) of 120 miles. Charging to 90% took very little extra time and would bring the range to almost 140 miles if you're only getting 1.43 miles/kWh.

 

[colmode]

[This was also posted on Reddit -- sorry if it looks familiar...]
I specifically chose the Gravity for range and hopefully towing range, and today I got to test it out. It did not disappoint. My GGT has 7-passenger and 21" wheels so a bit of a hit on range (not what I originally ordered), and my tow was from the Maryland suburbs of DC down to VIR in Alton, VA. I was towing a sports car on an open aluminum trailer, total weight 3500 lbs with another 500 lbs of "stuff" in the car. I removed the overhead tire rack and the 8 extra wheels/tires were among that "stuff" inside the cavernous interior of the GGT.

I had done one prior 83-mile tow and watched the miles/kWh gradually increase but started quite low at 1.05. Today it started at 1.17 and climbed gradually but consistently ending at 1.40 after 250 miles, and still rising.

The first leg was almost all Interstate with some traffic. 133 miles, battery went from 99% to 31% (81.6 kWh) - 1.63 miles/kWh. That would allow an initial pull of 176 miles. But I'll be more conservative until I have more experience - see below.

For my second leg (after a quick charge from 31->92% at a 360 kW charger over about 22 minutes while I had a snack), I went 110 very hilly miles on 64% (76.8 kW), or 1.43 miles/kWh. So conservatively an initial pull would be 171 miles, and subsequent pulls (charging to 80% and trying to charge again at 10%) of 120 miles. Charging to 90% took very little extra time and would bring the range to almost 140 miles if you're only getting 1.43 miles/kWh.

And no cruise control available, right?

 

[Dr K]

And no cruise control available, right?

You are (unfortunately) correct. I’ve posted about my right foot getting tired—on the thread about a “heavy” accelerator pedal. And I’ve messaged Lucid to allow ACC with the longest inter-vehicle distance. I believe that would be safer than what they have now—I’ve been towing with cruise control in various vehicles for at least 15 years!

 

[colmode]

You are (unfortunately) correct. I’ve posted about my right foot getting tired—on the thread about a “heavy” accelerator pedal. And I’ve messaged Lucid to allow ACC with the longest inter-vehicle distance. I believe that would be safer than what they have now—I’ve been towing with cruise control in various vehicles for at least 15 years!

I tried to get a definitive answer a few weeks ago. What the SA in Natick relayed to me was that cruise control (not necessarily adaptive) in tow mode was on the list of planned features, but with no date yet.
Competitors support towing with cruise, so Lucid might feel some pressure. I believe that Rivian revert to fixed-speed cruise, whereas GM supports adaptive.
This is probably held up by the need to test braking with a wide range of loads, and by the fact that people who tow are a smaller subset of Lucid owners compared to other brands.

The Gravity isn't a great long-range tow vehicle, exactly because it is so power-efficient. Aero drag from a trailer kills that efficiency, and that affects range a lot more than it does some GM monster that gets its range from a huge battery instead of (partly) a low drag force.

 

[Dr K]

But as I implied in my first post, I think the Gravity is actually a good long-range tow vehicle. Granted I'm not towing 5700 lbs with a tall, flat front surface, but I bought the car specifically to tow my race car and other than a Chevy Silverado with 205 kWh the Gravity's range is not to be beat. MUCH better than a Rivian which was the other EV I was considering.

 

[colmode]

But as I implied in my first post, I think the Gravity is actually a good long-range tow vehicle. Granted I'm not towing 5700 lbs with a tall, flat front surface, but I bought the car specifically to tow my race car and other than a Chevy Silverado with 205 kWh the Gravity's range is not to be beat. MUCH better than a Rivian which was the other EV I was considering.

Exactly my point. If I read you correctly you're losing something like 65% range. Something like a Sierra or Silverado EV loses a lower percentage of its range when towing, because it's a brick wall anyway and gets its range from the big battery. Aero drag is the biggest factor in towing, even with a relatively low-profile load. That ruins the Cd of the Gravity, but the difference is less with the trucks. So if long-range towing is one's most important use then big battery is the way to go. For all other uses the Gravity wins.

 

[Dr K]

Exactly my point. If I read you correctly you're losing something like 65% range. Something like a Sierra or Silverado EV loses a lower percentage of its range when towing, because it's a brick wall anyway and gets its range from the big battery. Aero drag is the biggest factor in towing, even with a relatively low-profile load. That ruins the Cd of the Gravity, but the difference is less with the trucks. So if long-range towing is one's most important use then big battery is the way to go. For all other uses the Gravity wins.

Even the Silverado takes a >50% hit with a towing range of 150-200 miles, but with a very expensive fast-DC charge taking 45 minutes 10-80%, it's an awful choice for long-distance towing. ICE or hybrid would be the way to go for that.

 

[jrreno]

I just completed a trip from Leland , NC to Rochester, NY roughly 750 miles in our Gravity GT. I was towing a 4500lb sedan on a dolly with the rear wheels turning on the towed vehicle. No cruise control available so I was driving the entire trip. I tried to maintain speeds from 55 to 60mph. At times I would find myself cruising at 75. The Gravity hardly noticed it had an extra load.
The NAV was completely inaccurate in terms of % SOC on arrival. It would state -32% on arrival at the beginning of a leg. About 3/4 of the way to the desitnation it was estimating +22%. I stopped paying attention to it and started using the Dynamic Range which provided a more accurate assessment of my available range. I averaged about 150 miles between charge stops. I used 512.5kwh for the trip. For reference the trip from home to Leland without the tow is 681 miles and used 288kwh.
The biggest challenge was finding trailer friendly charge stops. At some I just had to block several stations to get in charging position. Fortunately most of these were late at night and no one else was charging. In order to unhook the dolly I would have had to unload the car from the dolly, not really a reasonable option.
I’ll attach pics of a couple charge stops.

 

[Dr K]

It looks like you only got 175 miles total range—significantly less than my 203 miles. But the car I was pulling weighed only 2450 and the aluminum trailer 900 lbs. I did average 65-70 mph the whole trip (and occasionally 80 mph). With the car on a trailer I was easily able to disconnect the trailer for charging, although your first photo looked like an actual “pull-through” charging station!! Perhaps my trailer wheels had lower drag than the rear wheels of your car, or perhaps it was the weight difference.

I just realized I didn’t post HERE about further towing (from VIR to home, and then to the cage-builder for mods to my roll cage)—towing efficiency is now up to 1.7 miles/kWh, giving a 203 mile total range but still rising.

 

[jrreno]

It looks like you only got 175 miles total range—significantly less than my 203 miles. But the car I was pulling weighed only 2450 and the aluminum trailer 900 lbs. I did average 65-70 mph the whole trip (and occasionally 80 mph). With the car on a trailer I was easily able to disconnect the trailer for charging, although your first photo looked like an actual “pull-through” charging station!! Perhaps my trailer wheels had lower drag than the rear wheels of your car, or perhaps it was the weight difference.

I just realized I didn’t post HERE about further towing (from VIR to home, and then to the cage-builder for mods to my roll cage)—towing efficiency is now up to 1.7 miles/kWh, giving a 203 mile total range but still rising.

I did a lot of research before the trip to find as many pull through as I could. It seems counterintuitive but I wonder if higher speeds are actually more efficient? As you can see the car being towed did not present as much air resistance as a box trailer.
BTW, that pull through is an amazing Supercharger in Kenly,NC. The store is Kenly 95 and rivals Buccees for size and variety.

 

[TahoeMichael]

I just completed a trip from Leland , NC to Rochester, NY roughly 750 miles in our Gravity GT. I was towing a 4500lb sedan on a dolly with the rear wheels turning on the towed vehicle. No cruise control available so I was driving the entire trip. I tried to maintain speeds from 55 to 60mph. At times I would find myself cruising at 75. The Gravity hardly noticed it had an extra load.
The NAV was completely inaccurate in terms of % SOC on arrival. It would state -32% on arrival at the beginning of a leg. About 3/4 of the way to the desitnation it was estimating +22%. I stopped paying attention to it and started using the Dynamic Range which provided a more accurate assessment of my available range. I averaged about 150 miles between charge stops. I used 512.5kwh for the trip. For reference the trip from home to Leland without the tow is 681 miles and used 288kwh.
The biggest challenge was finding trailer friendly charge stops. At some I just had to block several stations to get in charging position. Fortunately most of these were late at night and no one else was charging. In order to unhook the dolly I would have had to unload the car from the dolly, not really a reasonable option.
I’ll attach pics of a couple charge stops.

Was the quest for trailer friendly charging stations just luck-of-the-draw at whatever station you stopped at? Or did you find a resource which helped identify trailer friendly chargers ahead of time?

 

[jrreno]

Was the quest for trailer friendly charging stations just luck-of-the-draw at whatever station you stopped at? Or did you find a resource which helped identify trailer friendly chargers ahead of time?

I did a LOT of research to plan the best route. I used plugshare, Tesla.com/findus and electrify america. I have 275,000 miles of travel with EVs since 2014 so I am familiar with charging infrastructure along the route I wanted to take. I bought membership in Tesla and EA to get the cheaper rates. I planned mostly Tesla because they are still the most reliable. I did a couple EA due to pull through availability. BTW, to get the membership rate you have to initiate charge through the app before plugging in for both EA and Tesla. I used Plugshare to identify candidates within the range I thought I could make with the towed vehicle. Plugshare usually has user uploaded pictures. I used Tesla to understand rates and power.

 

[Dr K]

It just keeps getting better!

I just did a short 40-mile tow (2/3 highway including plenty of traffic but mostly 65 mph, very hilly and winding the other third and driving at 30-40 mph) and my efficiency went up to 1.70 miles/kWh. That calculates to a range of the full charge at 209 miles, and "on the road charge" range from 80%->10% of 146 miles. If you take the extra few minutes to charge to 90% then we're talking 167 miles before your next charge.

There was no towing available when I ordered my Gravity, and only ONE report of towing I could find by the time I took delivery. I was hoping for a towing efficiency of at least 1.3 miles/kWh so I'm delighted with 1.7 (and it's still rising!). Unfortunately I didn't record the battery percentage prior to starting my tow...

 

[ke2]

What does towing do to the effiency of a ICE car? Does the MPG get cur by approximately the same amount? I've never towed anything in an ICE auto, always gotten a truck or van.

 

[Dr K]

What does towing do to the effiency of a ICE car? Does the MPG get cur by approximately the same amount? I've never towed anything in an ICE auto, always gotten a truck or van.

It depends on the vehicle. Towing the identical trailer with a Toyota Highlander (non-hybrid) lowers the mileage by about 1/3. Towing with a 150-series (or 1500-series for GM) pickup truck affects mileage much less but you're starting with lower efficiency. I once borrowed a friends BMW X5 diesel and it barely affected the excellent mileage at all. EVs generally take >50% hit on efficiency, with few able to tow further than 110-120 miles unless they have 200+ kWh batteries like the GM EV trucks. Gravity is known for efficiency but much of that is due to "slippery" design so it should take an even bigger hit towing than a brick-shaped vehicle, and that is why I'm so surprised that the Gravity's tow range is more than half of it's non-tow range.

 

[Pragmatic]

Years a go I towed a small u-haul box trailer, ~1000 lbs, 150 miles on the NYS Thruway with a 1990 Mustang (5 L, 5sp MT). Normally my FE for such a trip would be 23mpg, towing it was 15mpg.