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Tow Mode Charging

Tow Mode Charging

So was sitting around the campfire at my local state park. Thought to myself; retirement looks like an RV, pulling a Tesla. My buddy says "yeah it will have a generator so you can charge while you drive."

I thought about this statement informing him that Tesla's regenerative brake. This means in theory you can charge one while you pull it behind the RV. Obviously it takes energy from the tow vehicle in the form of additional load, but with many RVs like diesel pushers, that drag is very negligible. Whether its 4 wheels or two on a dolly that's for the engineers.

Would this really require more than a software update to use the rolling car to charge itself and then software manage trickle charge keeping it topped off. Seems like a game changer for those living the RV lifestyle. You might be surprised how big that market has gotten the last 10 years.

Roll up to the campground, 200+ miles of charge ready to go, model 3, model s, or even x. It doesn't matter! I'm all in.

Earl and Nagin ... | July 16, 2017

This will probably work today if someone is sitting in the car. It isn't particularly safe. I'm not sure why you'd try to charge by towing though. Since you've undoubtedly stayed at an RV park the preceding night, you could have charged your Tesla using the NEMA 14-50 (aka "50 amp RV outlet") at the RV park - electricity cost already included in your camping fees so totally free to you.
I don't know why Tesla would put in an automatic mode for charging while towing since my suggestion is much cheaper for you.

reed_lewis | July 17, 2017

Also if you were pulling power from the wheels spinning, the Tesla would be harder to pull because it would be like the brakes are applied all the time.

So you would use more gas in the camper to pull the car which means it would cost more to charge than the gas cost.

There is 'free lunch' where you get energy for no cost. There has to be something to create that energy.

The only way it could possibly work is it the camper could notify the car to apply the 'brakes' and the car used regeneration as braking power.

nadurse | July 17, 2017

I could see this being useful if you were in the wilderness and had access to only a few gas stations, but the RV would take somewhat of a hit on its mileage since you would basically be towing the Tesla with its brakes on.

But if you were gonna go to a campsite with electric hookup then you could just charge the car there when the RV doesnt need power.

Or charge the Tesla with your onboard RV generator, would probably be equally or maybe more efficient than adding more drag to your RV.

Nexxus | July 17, 2017

As @reed_lewis said, if the RV were to notify the Tesla that it was braking and for the Tesla to apply the regenerative braking at the same time, it could charge the Tesla somewhat and save the brakes on the RV at the same time. So only regenerate when the RV is slowing down applying its brakes.

Should_I | July 17, 2017

This would also be pretty hard on the Tesla tires unless the regeneration level were set very very low. This is aside from the good points already made.

How about we get out in the weeds and say just have the wife "drive" the Tesla on the downhill stretches of the trip. If out in the Rockies you might actually get some range out of detaching the Tesla and coasting down the hills.

dannyesmith3 | July 17, 2017

I covered most of these counter arguments although apparently not that well.

For the one I didn't. Almost all Midwest campgrounds only run 30a pedestals, and only one of them may be used per site, typically for the RV itself. Additionally many of the RVs like class A, don't even bother hooking up purely from a risk and effort point of view, many of the campgrounds don't have stable power as usage increases. So a lot of class A don't want to risk under-volting their equipment which is a VERY REAL problem.

Excluding that, I did mention it would create additional load on the tow vehicle. However for most diesel pushers that load doesn't change the economy of the coach that much, and for gas its fairly marginal at that size.

As far as tire wear, it wont be that significant beyond just the mileage on the tires themselves. The car doesn't have to fully charge in 50 miles, the torque is no where near the forward torque required to blow the doors off the V8 crowd =).

Shock | July 17, 2017

Certainly the regenerative system wasn't designed for constant use at this level. Whether it can withstand charging for long periods of time or not I have no idea. This idea you have I've seen posted in the past, such as at the Nissan forum. Others have even posited the idea of towing a trailer in an electric car with the trailer running a generator to charge the car real-time in cases where it is otherwise going to run out of range.

Should_I | July 17, 2017

On the tire wear you are not considering consistency of load. Yes a quick 0-60 jaunt is a lot more load on the tire than a slow regenerative load BUT the 0-60 is brief, an regenerative load is more than sustained speed load like highway miles. You are trying to compare 4-5seconds of high load to hours of . I am looking at P85s so these numbers are based on that, you are comparing a 353kwh load for seconds to even at max regen which I am sure is wrong for this idea but is what 60kwh and this regen would need to be sustained for hours. IF this can be done I suspect it would be dialed well below the 60kwh rate though. 353kwh for 4 seconds is not the same as say 15kwh for hours(above whatever rolling load is). The later could potentially even cause heating into the tire carcass not just in the outer tread.

From my perspective as a lifelong manufacturing worker current low level engineer. Tesla would need to do testing and software development to enable all this, aside from the fact the car is not even rated to flat tow any distance as is. Lots of cash outlay for a niche group, may be a growing trend but not a big enough group to justify the cash, time and resources, a few years from now when things plateau some and they have some engineers that need something to do, maybe.
There are relatively few vehicles rated to flat town behind an RV because the transmissions need engine rotation to lubricate things, based on that I would think the Teslas well suited but they likely have some reason not to rate them for it.
Miles flat towed are still miles put on a car, engine running or not, even on a trailer miles are put on the suspension, wear and tear on shocks, springs and bushings.

This stuff is "easy" to handle from the perspective of some academic, financial wizard, whatever never gotten your hands dirty viewpoint the average Tesla owner has, but a lot harder when considered by someone who knows what it takes to develop and MAKE things.

Bradtc | July 17, 2017

Those crazy Russians have already tried it....

http://insideevs.com/watch-tesla-model-s-get-charged-towed-video/

DTsea | July 17, 2017

You would have to sit in the car as it will go into park with no one in driver seat. Which i believe is illegal when towing.

Dwdnjck@ca | July 17, 2017

I think it would be nice is Tesla simply made the car towable. My brother owns a high end RV and travels in it more than half the year. He would love to be able to tow an S or X. I have visited him at RV parks and unplugged his RV to charge up my Tesla. If needed he could run the RV gen set while I was plugged in.

grins.va | July 17, 2017

The Russian video ended just before the semi braked and the Tesla crashed into it. No problem, my brother fixed it. LOL.