Model S + Honda 240v Generator = Unlimited range?

Model S + Honda 240v Generator = Unlimited range?

I'm concerned about the range of the Model S which might limit it's suitability for road trips. Would it be possible to have a trailer hitch with hitch-platform and carry a Honda 240v generator and somehow power the car while driving at highway speeds? I know that this would not look sexy, but it would provide me a level of comfort that I could use the car for more than 160-200 mile trips.


DouglasR | January 19, 2013

There have been other threads on this topic (use to find them). Short answer: no, the car cannot be driven while charging.

Sudre_ | January 19, 2013

Think of it this way. 300 watts per mile average is the least you can expect from the motor. So one hour of driving at 60 mph would be on average 18kWh. Most people are getting more like 380 and above but if you could get 300 watts per mile you would need a generator that can handle a continuous load of 18kWh. The surge peak for the generator would have to be around 300kWh for acceleration. If I recall correctly it's 768 watts per horse power but the motor is three phase so there is formula to calculate the actual number.

If it was so easy to just throw a generator on a trailer the Volt would have been a much easier car to design.

GoTeslaChicago | January 19, 2013

No, but if you put solar cells in front of the headlights you can recharge the battery as long as you drive with the headlights on. : )

DouglasR | January 19, 2013

Sudre, I think you're mixing kW and kWh. The continuous load under your assumptions would be 18 kW, not 18 kWh. It would obviously need more than that as peak capacity, but 18 kW is essentially what you would get from twin chargers using 80 amps @ 240 volts.

The problem is that, towing a trailer, you would consume MUCH more than 300 watt hours per mile (not watts per mile).

ghillair | January 19, 2013

Why not just put the ICE generator in the frunk and call it a hybrid.

O wait that is 20th century.

MarkV | January 19, 2013

As noted already you cannot charge and drive at the same time. Model S also does not allow any sort of trailer connection. Of course you could do something and void the warranty. AAA has instituted a fleet of mobile chargers that will "save" you in a pinch should you get caught.
For the time being (that is before the supercharger network is complete) we just have to adapt to planning better and stopping more frequently when attempting cross country travel. Sort of a throw back to the days when gasoline stations were not on every corner or even in every town for that matter.
You could have a friend or relative deliver your generator to your location if you still want your own unit. Be sure to get a high quality generator because if the sine wave produced is not high enough quality the car will simply reject the connection.

Superliner | January 19, 2013

Really?? that's like having a fuel truck roll along side your ICE and refuel it as you drive!

You could just buy a Honda Civic and use the remaining $80,000 for gas. Or......

Buy a Volt or Karma or "other" Series Hybrid, they already do this.

Superliner | January 19, 2013

@ GoTeslaChicago

Now THAT's a good one BwaaHahahahahaha!! I'll have to remember that for the Generator on the wheel, or wind turbine on the roof crowd. They always seem to forget that any action causes an equal and opposite reaction. So your best outcome is a ZERO sum gain.

Getting Amped Again | January 19, 2013

ghillair | January 19, 2013

Why not just put the ICE generator in the frunk and call it a hybrid.

No that's called a Chevy Dolt.

EK | January 19, 2013

This forum really needs thumbs, or like dislike

like @ GoTeslaChicago

DouglasR | January 19, 2013

You could also just put your Model S on a flatbed truck and drive it around: unlimited range!

Seriously, Honda's biggest "portable" generator is rated at about 9 kW, 37.5A at 240V, and weighs 403 lbs dry. The tank holds 8.1 gal. (another 65 lbs) and it will run for 4.6 hours at rated load. So with a full tank of gas, and 4.6 hours of charging, you could theoretically add 41.4 kWh to the battery. How far that would take you is anybody's guess, but the added weight and drag would surely cut your range way back. Rated energy consumption of about 300 watt-hours/mile works out to 3.3 miles/kWh. If the trailer lowered your mileage by 1/3 to 2.2 miles/kWh, your total range would be 269 miles ((85 kWh * .95 + 41.4) * 2.2)-- about the same as you would get from a range charge without the trailer. In other words, you could drag the trailer for the car's reduced maximum range of around 177 miles, then sit there charging for 4.6 hours to add back 41 kWh, then drag the trailer another 92 miles until you are out of charge again. While it is true that you could probably keep going indefinitely by stopping at a gas station every 80 miles or so and charging for four hours, you would be averaging under 20 miles per hour. Frankly, I'd rather check in overnight at a motel with a charger. Or take a plane.

Brian H | January 19, 2013

GTC +1 works.

TikiMan | January 19, 2013

I'm attaching a giant boat sail to my P85, so I can let it re-gen the battery after 300 miles. Now if I can just set Google maps, so I can avoid all the over-passes, I will be in business!

Brian H | January 19, 2013

More likely in involuntary care, than in business. >:P

shs | January 19, 2013

I own an 18 kW backup generator and it is big and heavy, not to mention the even bigger propane tank that powers it in the case of a grid power failure. It does put in perspective how much power is actually stored in the MS's battery.

The real issue with range and long trips is whether one fills up at a gas station or a supercharger or some other EV charging station. Right now, there are a lot more gas stations and so, for a while at least, serial hybrids may make some sense. I would rather bet on the future though, and go with a BEV and hope that the EV charging fills in the current gaps. (pun intended.)

Superliner | January 19, 2013


MwaHahaha!! Overpasses? Still.. The laws of physics would reach out to get ya' The wind might move the car but if you add drag as in regen at a rate that would do you any good?? Hmmm How big is that sail again lol!!

Robert22 | January 19, 2013

The sail can be kept small if the military surplus JATO (jet-assisted takeoff) rocket is properly bolted to the chassis...

cprenzl | January 19, 2013

I think that is what superchargers are for, I'm sure you can take another car on your long trips till the end of the year when they cover the US completely

DocDog | January 19, 2013

When I was a small child, I remember my mom running out of gas on numerous occasions b/c she would not plan to get gas when she was getting low, and the nearest (open) station was beyond "the range" in the tank. This is going to happen for a while with electric cars now. Today, running out of gas is quite rare (even for my mom), b/c there is a gas station every 5 miles nearly everywhere we travel. I believe that it won't be long before we have sufficient high amperage electric stations to make "running out of electricity" an unusual event too.

Anthony H | January 19, 2013

@GoTeslaChicago, I laughed.

@pashaw01, I'm sorry. This is a tough audience.


Brian H | January 19, 2013

Which direction was the JATO's thrust vector, again? I intuit you might have a hard time overcoming it with the exhaust hitting the sail ... <;)

Superliner | January 20, 2013

I hope you're kidding Robert, As Brian says if the thrust is directed toward the sail it's a wash .. they apply force to the object in opposing directions "assuming the sail material and mounting structure can withstand the force of jet exhaust" not to mention the heat lol!! One more for the Generator on the wheel theory! BaHahahaha! Physics will not allow a free lunch.

Brian H | January 20, 2013

Like the old idea of blowing on the sail in a sailboat. The only way blowing would help is if you made like a jet engine and blew backwards, probably spinning around to inhale facing forwards, and repeat. You could combat the serious hyperventilation by swinging a sweep oar back and forth all the while, to help.

Take lots of time out to eat; you'll probably burn 6-10,000 Calories a day! Lots of Big Macs, supersized fries, and milkshakes would probably do it. Every couple of hours.

Timo | January 20, 2013

@Brian H, Like the old idea of blowing on the sail in a sailboat.

Mythbusters tested that. For their surprise sailboat did move forward with fan blowing to the sail at the back of the boat (and it did work in any direction in that lake, so this was not a case of actual wind blowing to the sail).

Odd thing, airflows can sometimes do tricks that are unintuitive.

Sudre_ | January 20, 2013

I think the Mythbuster thing actually worked like an air-boat except the air was ricochet'd off the sail. It would have worked better to just turn the fan around and let the air-boat work normally.
If you take a fan and connect a giant 20' long rubber hose to the output of the fan the boat will go opposite where ever you point the rubber hose no matter where the fan actually is..... much like a rocket.

Sometimes I really wish it wasn't so hard getting the crazy Monty Python circus act out of my head and onto paper.

pashaw01 | January 20, 2013

This is great fun, thanks for the replies all! I expected much worse...

Superliner | January 20, 2013

Oh Brother! Just drive Model S responsibly in an efficient manner and forget sails, wheel generators, solar panels in front of headlamps etc.

Physics prevents it. You simply cannot extract enough energy from the propulsion force of a vehicle "or any vehicle" to make self sustaining motion. Any drag introduced to generate energy is directly opposed to propulsion therefore you need to use more energy to overcome the added drag and remain in steady motion. The additional energy consumed to overcome generation drag offset hence a zero sum gain.

If it were that easy we would all be driving perpetual motion cars.

Brian H | January 20, 2013

How much power is delivered to the fan blades? How efficient is the forward motion? Lots, and not very.

edpalermo | January 20, 2013

That is a ridiculous question, IMHO .

Timo | January 20, 2013

@edpalermo, which question? We are talking about sails in roof of a car, so I think any question about that concept is going to be ridiculous. I think that is the point.

TikiMan | January 20, 2013

Scratch the boat sail, I'm putting this guy in my frunk!...

Superliner | January 20, 2013

@ TikiMan

At last... The perfect range extender lol!!

Brian H | January 20, 2013

If he buys a Tesla, will he need a battery?

glenn.berry | January 20, 2013

I have wondered why there is not an option to have some solar PV cells on the surface of the roof of the Model S. The surface area of the roof would probably allow you to get perhaps 300-500 watts of output, depending on the efficiency of the cells.

This could give you a little bit of extra range, or help diminish the range loss from battery pack heating and cooling.

Plus, it would sort of look high-tech...

Brian H | January 20, 2013

About the umpty-twoth time that has been suggested. Costs about $5K on the Karma, max 300watts in full sun. Some of the most expensive and unreliable power ever, at about $20/watt. BAD idea. Just show.

jbunn | January 20, 2013

A sail, for me. When the wind doesnt blow, ill use compressed air to fill the sail. I envision someday a nationwide network of compressed air stations for Tesla sails to extend range.

Brian H | January 21, 2013

Don't forget the little wind turbines to tuck under the nose to generate even more power from the forward motion. In a strong headwind, at least.

Flaninacupboard | January 21, 2013

A more serious question, an air source heatpump extracts heat energy from the air, with roughly 300% efficiency (1kwh of electricity driving the pump generates 3kwh of heat energy). Could you use thermocouples to turn this scavenged heat energy into electricity? If the thermocouples (or some other form of turning heat into electrcity) are more than 33% efficient you get a net gain...

Mark E | January 21, 2013

@Flaninacupboard: the number I've seen for heat pump efficiency is 200% rather than 300%.

Thermocouples/peltier effect devices are generally very low efficiency, although I was reading one company claiming to be working on one with up to 80%. I'll believe that when I see it, but would love for it to be true as there is waste heat everywhere to be captured, including on the back of normal PV solar cells.

holidayday | January 21, 2013

I'm concerned about the range of the Model S which might limit it's suitability for road trips - Pashaw01

Welcome to the next step in 21st century transportation!

Although I enjoyed reading the solutions as well as your generator item, this question really extends to a major point in American freedom.

Q: How do I drive 600 miles? A: You have to rethink your driving assumptions.

First: you never have to gas up the car again.
Second: Charge as often as you can. If you can take advantage of the SuperChargers, do that. If you can't, use resources to find electric plugs / outlets / etc to charge along the way.
Third: Until the infrastructure is there, you'll have to do more work before a road trip. Campgrounds, RV Hookups, and other Telsa owners may let you use their locations to charge. Their are multiple blogs about how people have taken roadtrips in their new Model S.
Fourth: It takes much longer to charge than to refill gas, so expect longer trip times. Unless you already make frequent stops and/or take leisurely meals, you probably can go 300 miles, stop for gas, then go another 300 miles. (or 350 - 400 if you're like me).

Until we get Mr. Fusion available, this will be the new road trip paradigm.

olanmills | January 21, 2013

Congratulations! You invented the first vehicle powered by a combustion engine!

I forgot what I was saying...

mskinner | September 29, 2015

from a novice, why can you not mount alternators in the forward trunk that are powered by the turning of the front wheels. If you split battery into two half's the generators could then charge one half while the car drives on the other half. Software could control the battery selection and toggle between them as one drains and the other is recharged while driving. No need to power generation with gas or diesel its done from motion of front wheels. As a Model S owner I would be happy to give up the front trunk to allow this sort of modification. Would that not increase the range even if the charging is not capable of full charge. this way you utilize the forward momentum of the car itself to generate the power. trick is splitting the batter into tow sections one driving and one charging.

PS love my Model S

Tigger | September 29, 2015

mskinner - oh dear, please go back to school and re-take Physics :-)

DTsea | September 29, 2015


The power you take off the front wheels makes the main motor work harder. All that would do is discharge the battery faster.

Linus | September 29, 2015

@ mskinner
What you are proposing is called a "perpetuum mobile". Please google it.

hammer @OR-US | September 29, 2015

It is really sad that someone who has enough money to own a Tesla has such a dismal science education.

Rocky_H | September 29, 2015

@mskinner, As others mentioned, having a device that creates its own energy as it moves in a neverending cycle is usually referred to as a perpetual motion machine, and it is provably impossible. And the same principle applies as to why it cannot even "extend range" either. It can only lose energy. It's not just something that no one has figured out how to do yet. It absolutely cannot happen. This idea gets brought up every week either here on this Tesla forum or on Tesla's Facebook page (it showed up there just a couple days ago). I have saved this full explanation that I can paste in to explain why this cannot be done.

A motor or a generator/alternator are basically the same thing, just depending on which direction you are running it. They convert rotational kinetic energy to electrical energy or vice versa. There have been many people who have made your suggestion about using a generator to recapture energy from the motion of the car. What they miss is that they think they can get the generator to spin with no effort--not slowing the car. But it is a conversion device. It is going to take physical force to turn it if you are to get any electricity out of it.
So you take energy out of the battery to run the motor (conversion1) to move the car. Then, you take some of that motion energy to turn your generator (conversion2), slowing the car to recharge that back into the battery. That is just converting energy back and forth in a closed circle, and each conversion is always a little less than 100% efficient, so you have just lost some energy for no purpose.
Since running generators does slow the car some, every hybrid and electric vehicle does use that when the car needs to slow down anyway. Why just waste that energy grinding brake pads on metal, when you can convert that energy and store it when the car needs to slow down? They call it regenerative braking.
I do get how people get confused when they are thinking of an alternator in a gas car, because it's less apparent what is happening. The alternator doesn't seem to affect the running of the engine, but it actually is. Alternators, air conditioning compressor belts, serpentine belts, power steering pump belts, etc. that are being spun by the engine are all taking a little bit of force to turn, so they are sucking away from the energy of the drive shaft. It's just that it is hard to measure the half a mile per gallon loss of efficiency that each is causing. But it is consuming more gas running those, which you refill externally when you fill the tank.

notblueclk | September 29, 2015

This is range anxiety at its worst.

There are only three places on the US map where you don't have access to either a Tesla Supercharger or a Level 3 CHAdeMO: Texas (West by El Paso), North Dakota, and West Virginia.

CHAdeMO adapters are $450, and you can rent or borrow one at many locations. In fact a number of CHAdeMO sites have them available to use while you're there.

mskinner | September 29, 2015

The insults were not warranted. I was just asking a question that appears to have been asked by others before. You are right I never finished high school but I am very successful I own multiple businesses and employ 100's of people, if you ever apply for a job please remind me of your comment so I can show your over self indulgent butt to the door really fast.

I still love my Tesla

overthewoods | September 29, 2015

Just imagine the possibilities: