Silverado EV RVer

[BigBillSD]

I personally would wait a bit before buying an EV to tow a trailer. My next car will be an EV, I won't buy another gas powered car. I had the original Leaf and it too was the best car I ever owned.



But, while camping at Champoeg State park last month I talked to a guy that towed a 23' trailer with his model 3 Tesla. He had been doing it all summer, but mentioned it looses 70% of its range. 300 miles of range became 70 miles when towing that small trailer. He mentioned it wasn't much better than that with a very small box trailer. He thought it was due to the aerodynamics of a sleek car and adding a big square brick behind it. I'm don't know what it was, but loosing that much range was a bit shocking.



-Bill

[radar]

Originally Posted by BigBillSD

I personally would wait a bit before buying an EV to tow a trailer. My next car will be an EV, I won't buy another gas powered car. I had the original Leaf and it too was the best car I ever owned.



But, while camping at Champoeg State park last month I talked to a guy that towed a 23' trailer with his model 3 Tesla. He had been doing it all summer, but mentioned it looses 70% of its range. 300 miles of range became 70 miles when towing that small trailer. He mentioned it wasn't much better than that with a very small box trailer. He thought it was due to the aerodynamics of a sleek car and adding a big square brick behind it. I'm don't know what it was, but loosing that much range was a bit shocking.



-Bill

Good morning Bill. Yah that does sound like a lot. We lose close to 50 percent but we are kinda used to that as we lost about the same when we towed with a grand Cherokee.

I think the shape of the trailer affects it a lot. We have friends with a similar but lower and narrower version of ours and they only lose about 40 percent.

Here’s ours. Cheers.

[BigBillSD]

Originally Posted by radar

I think the shape of the trailer affects it a lot. We have friends with a similar but lower and narrower version of ours and they only lose about 40 percent. Here’s ours. Cheers.

Your's looks a lot more aerodynamic and quite a bit smaller than what he was pulling. I wish I had taken a picture of it.

[radar]

Originally Posted by BigBillSD

Your's looks a lot more aerodynamic and quite a bit smaller than what he was pulling. I wish I had taken a picture of it.

Yah. We have seen and talked to a few people towing the bigger more boxy trailers behind their EV SUV’s. They usually have disappointing results. For these smaller SUV’s low profile is the way to go regardless of the fuel. Our towing experience is quite good and we have travelled over 15000 kilometres across Canada and all over BC this summer. Next summer we are doing more of the BC interior and coast, and then in the fall we are taking the US west coast along the ocean down to Malibu and then cut over and down to Puerto Penasco Mexico for part of the winter. Should be fun.

[oldenavy]

Originally Posted by DrivingDan

I use the distance range measurement on my Bolt, common on Chevy’s - the Silverado will have it. Brings up an interesting point though is does that calculation recognize when you’re towing and include that?

Yes I’ve seen people doing crazy tests running their battery to zero, on some models you can see that effect but it’s rare AFAIK. A BEV battery is babied and has its own climate system and tons of control microelectronics. Batteries are a dark science, so the algorithms have to guesstimate the status - to a degree. What they probably do is run lots of tests from which they build models that the algorithms use.

Well they usually have a 1 speed gear which goes something like 1-1 and a fraction or something. But gears are expensive and waste energy and the motors don’t need it unless you want a super car. So the high end Teslas do a trick where the motor on the back is geared for low speed, and the motor for the front is geared for high. At low speed the power goes to the back, at high speed it goes to the front motor. Electric motors slowly lose torque at high rev, so doing this gives you insane torque across the speedometer. The new Dodge Challenger EV muscle car concept has a gearbox, probably for this reason.

On my Bolt you notice that at freeway speeds it doesn’t have the oom-pah it has at zero, but of course it’s designed as a joe average car (which is a heck of a lot of fun to drive).

Will do - thanks for the tip!

Aero is complicated, but I believe the low hanging fruit is in the dead space between the vehicle and the trailer. This creates a partial vacuum which is drag - just some kind of simple panel between the two to keep that laminar flow would do wonders. If you look at the Tesla Semi you’ll see they did it for exactly this reason. Otherwise long lines help so this would actually be a boost. It’s the same with yachts - a long waterline is a faster boat.

Just found this thread and though I'd try and clear up a few things:
- The reason for no gearbox in most EV's is because electric motors produce their maximum torque across the whole speed range from zero rpm up to their max rated rpm, very unlike IC engines that have a torque peak somewhere (different between gas or diesel) and of course can't produce any power below their idle speed, hence the need for a fluid coupling/torque converter in modern automatic transmissions and multiple gears to keep the IC engine in it's torque (or power) band. Constant torque means the power output from the motor increases linearly with speed (power = torque x speed), UNLESS you do a control scheme called field weakening which I won't bore you with the details of.

- The losses in the electric motor come primarily from the I^2R losses in the stator windings. Additional losses come from windage & friction from the air in the airgap & bearing friction but that won't be as large as winding loss except for extremely high speed motors that usually arent' found on EV's. Most EV motors are permanent magnet type, so there is little loss in the rotor.

- I don't know this for sure, but would expect EV batteries to have a battery monitor, similar to the one I installed when I put Li batteries into my Airstream trailer. That was a current shunt with an algorithm that essentially 'counted amps' going either in or out of the battery. If you know battery capacity and count amps in/out, you get a pretty good estimate of SOC. However, this gets complicated by the fact that a battery's capacity is also a function of how fast you charge it and a variety of battery-specific properties.

- Others have correctly noted that the charging process is nonlinear. Modern chargers have 3 charging stages. When you pull in with a low battery, it starts out in constant current (or bulk) mode. That gets you to the 80% level people have been discussing (more or less), then when the battery voltage reaches a threshold, the charger shifts into constant voltage mode to take it to a full charge. Once the charge is complete, the charger shifts into a 'mantain' mode, which you'd likely never see on a highway stopover. For more details on charging: https://batteryuniversity.com/articl...ng-lithium-ion Expect to see charging times decrease significantly in the coming years. I'm aware of ongoing battery research into cell materials that will allow charging at rates up to 5C (defintion of C-rates: https://batteryuniversity.com/articl...what-is-c-rate)

- The airflow around any vehicle going at highway speeds will NOT be laminar. Fluid flow becomes turbulent above a Reynolds number of about 2000 (Re=velocity x length/ kinematic viscosity). A 15' long car traveling at 60 mph through air gives you a Re ~8.2 x 10^7 which is WELL into the turbulent flow regime. If you have a longer vehicle (or one pulling a trailer, the L gets larger and so does Re). https://www.engineeringtoolbox.com/r...ber-d_237.html

- This is NOT the same thing as with yachts. The hull speed of a boat/ship (i.e. max speed it can travel without planing on top of the water) is governed by the Froude number (Fr = Velocity / sqrt(gravity x length)), not the Re. https://www.engineeringtoolbox.com/f...ber-d_578.html

As for the OP's plan, sounds great. EV technology is improving rapidly and with the growth of that market, we'll see charging stations popping up everywhere in the coming years. Recall that 100-ish years ago, there weren't many gas stations but now they're practically everywhere.

[radar]

@Oldnavy.

Interesting post. Thanks for posting.

[carybosse]

Originally Posted by oldenavy

....

- Others have correctly noted that the charging process is nonlinear. Modern chargers have 3 charging stages. When you pull in with a low battery, it starts out in constant current (or bulk) mode. That gets you to the 80% level people have been discussing (more or less), then when the battery voltage reaches a threshold, the charger shifts into constant voltage mode to take it to a full charge. Once the charge is complete, the charger shifts into a 'mantain' mode, which you'd likely never see on a highway stopover. For more details on charging: https://batteryuniversity.com/articl...ng-lithium-ion Expect to see charging times decrease significantly in the coming years. I'm aware of ongoing battery research into cell materials that will allow charging at rates up to 5C (defintion of C-rates: https://batteryuniversity.com/articl...what-is-c-rate)

...

I think this is the piece of this puzzle that causes me to hesitate further. Everyone keeps talking about battery technology and charging technology is going to improve: But that means, if I purchase an EV today, by tomorrow it is obsolete.

The EV manufacturers are using the I-Phone business model to roll out their products: Every 2-3 years they expect buyers to just have to own the latest and greatest upgrade.

It definitely would seem to me that leasing an EV may be a wise choice as opposed to a purchase.

[radar]

Originally Posted by carybosse

I think this is the piece of this puzzle that causes me to hesitate further. Everyone keeps talking about battery technology and charging technology is going to improve: But that means, if I purchase an EV today, by tomorrow it is obsolete.

The EV manufacturers are using the I-Phone business model to roll out their products: Every 2-3 years they expect buyers to just have to own the latest and greatest upgrade.

It definitely would seem to me that leasing an EV may be a wise choice as opposed to a purchase.

Maybe. But even 10 year old EV’s have really good resale prices and the tech has changed A LOT in the last 10 years.

[SnowG]

These guys make a teardrop for EVs that has enough battery power to offset your losses due to towing - https://coloradoteardrops.com/ev/


They could add more power and I think they should, but for now it is just enough charging power to help offset the losses in range due to towing weight.

[radar]

Originally Posted by SnowG

These guys make a teardrop for EVs that has enough battery power to offset your losses due to towing - https://coloradoteardrops.com/ev/


They could add more power and I think they should, but for now it is just enough charging power to help offset the losses in range due to towing weight.

Thankyou for the link.

It’s interesting but for us I can’t see it being an attractive product. And here is why. And for background we tow a teardrop trailer with a Tesla.

This trailer can not charge the EV while in motion. So it can only charge while stopped.

It uses an L2 J1772 to charge the EV. So max 11 kw charging rate. So at minimum 5 to 6 hours.

The trailer is a nice low profile unit but it has no bathroom or made up bed etc etc. A trailer with this low of a profile would have much less of an affect on range than something like ours (which cuts the range in half). It just seems if they were going to go thru the trouble of adding probably 50 kWh of battery capacity to a trailer to offset range loss they would have made a little bigger trailer.

From experience finding two charge stations in the right configuration to charge both units at the same time would be a challenge.

Anyway. Interesting concept. Thanks for posting.

[kdauto]

Yeah, I don't see that tiny trailer as even an upgrade from a nice pop-up. No bathroom? No standing up in that thing for me. May as well live in a minivan.

Radar, they do say no charging while driving, but the whole idea is kinda off to me. I'd have thought they'd use a motorized axle assembly that is available through Magna. It's quite smilar to what Toyota and Mitsubishi hybrids use at the rear axle of their SUVs and vans. That would help autonomy and be more efficient and timesaving as you don't need to stop for a recharge of the tow vehicle.

[radar]

Originally Posted by kdauto

Yeah, I don't see that tiny trailer as even an upgrade from a nice pop-up. No bathroom? No standing up in that thing for me. May as well live in a minivan.

Radar, they do say no charging while driving, but the whole idea is kinda off to me. I'd have thought they'd use a motorized axle assembly that is available through Magna. It's quite smilar to what Toyota and Mitsubishi hybrids use at the rear axle of their SUVs and vans. That would help autonomy and be more efficient and timesaving as you don't need to stop for a recharge of the tow vehicle.

Yah that would be an improvement. But it gets goofy as soon as it involves charging and driving at the same time. Any charge standard, CCS, Chademo, J1772, NACS etc, all prevent the vehicle from moving if a charge connector is detected. Any attempt to modify the software that does this would void the warranty of the vehicle. And that’s not even getting into the BMS software having to deal with charging while drawing current for motive forces. I’m not an expert in this but I see challenges there.

JMHO.

[kdauto]

Originally Posted by radar

Yah that would be an improvement. But it gets goofy as soon as it involves charging and driving at the same time. Any charge standard, CCS, Chademo, J1772, NACS etc, all prevent the vehicle from moving if a charge connector is detected. Any attempt to modify the software that does this would void the warranty of the vehicle. And that’s not even getting into the BMS software having to deal with charging while drawing current for motive forces. I’m not an expert in this but I see challenges there.

JMHO.

Yes, that's why I'm saying a motorized travel trailer is probably the best solution at this time. Magna makes these bolt-on motorized axle beams. It should be a relatively simple device once the battery space issues are resolved.

When you get to a charging station,put a charge line on the tow vehicle and another on the trailer.

[DrivingDan]

Update on further learning and thoughts.

Pricing: GM has released the pricing of the upper trim WT (Work Truck) which will be the initial fleet only release. The long range battery is only available on the 4WT which is about $80k. Lots of consternation around this pricing, does that imply a 400mi regular model will be at least that much or more? Unknown, but between early adopter tax and recent automotive price pressures it doesn't look good. Large concern. Solution, wait and see.

Tongue weight: The biggest technical issue appears to be tongue weight, which is either 800 or 1300 lbs depending on model/trim. That doesn't give a lot of wiggle room - 10k is plenty for most trailers but 1300lbs is tight, after you add the tongue weight and a couple passengers. I'd like to put a bed topper on which would be a couple hundred pound probably, well pretty soon you run out of capacity. Medium concern. Solution, have to travel lightweight, put as much in the trailer.

Charging: This appears to be, well not quite a non issue but not too much of one. I've done a lot of scenario planning, comparing against existing and proposed NEVI charging and it appears that you can travel through the US and Canada pretty freely, certainly so as NEVI charging comes online (along with other private investment from EA, EVGo, GM Flying J Ultium, etc). Small concern. Solution, don't worry about it.

Otherwise I've also looked deeply into improving aero. Conclusion is the biggest benefit is simply driving slower - 55-60 is my preferred speed anyhow. Believe it or not I think the second biggest easiest benefit would be putting a small boat on top of the cab flush with the windshield. This lifts the airflow to about the same height as your trailer, with the added benefit of extending behind the truck depending on the length, creating a continuous fairing much like a semi. Downside is with that hauling capacity it's impossible.

Useful aero information

Swapping Fuel for More Beer on your next Caravan Holiday