# Gas Trailer for Electric Cars?

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1. Aug 13, 2016

### Algr

So I was reading about Tesla's plan for battery swapping. I didn't think that was such a great idea, since you would be leaving behind something that was a good fraction of the cost of the car. Might there be a better way?:

So, it's the future: You've been driving around town, and used up half your cheap car's 90 mile range. (Not a Tesla, obviously.) Suddenly there is a big crisis-or-opportunity, and you need to jump on the highway and get somewhere 200 miles away as fast as possible! There is no need to go home first, (which is the wrong way anyway.) So what can you do?

Answer: You drive to the nearest rental place and have them latch a gas trailer to the back of your car. This device would be a gas generator plus tank, and would charge your battery while you are driving. (I assume, it would need to generate power faster than your car can consume it at highway speeds.) It effectively turns your car into a hybrid. But the advantage is that the car would cost less, and you wouldn't need to carry the weight of the engine and tank around except on the days you'd need them. (Maybe 3 days a year for most people?)

So my question is: How big would such a generator need to be? Could it attach to a hitch like a carrier rack? Or would it need it's own wheels like a trailer? (I'm assuming that the latter would make the car more difficult to drive.) I suppose the government would have to mandate a standard plug for power and brake lights. How difficult would that be?

2. Aug 14, 2016

### billy_joule

3. Aug 14, 2016

### Algr

Okay, if this has always been around, then why was everyone freaking about range anxiety?

4. Aug 14, 2016

### billy_joule

I'm not sure who's freaking out but a trailer is probably not a viable solution for most people, storage, cost and convenience are concerns, which is likely why genset trailers have remained a niche product. In my country, trailers require ongoing costs for registration and safety testing (like other vehicles) so owning a trailer for just a few days use a year is not appealing. Maybe people who want an LEV and are concerned about range buy a hybrid? Many can be run in electric mode only can't they?

5. Aug 14, 2016

### Staff: Mentor

Sounds like things the Nazis did in WWII

6. Aug 14, 2016

Staff Emeritus
This isn't practical.
1. They cost $15,000 and up. 2. Many EVs have interlocks so you can't drive while charging. This has the side effect of prohibiting charging while driving. So you need to drive, stop, charge, drive, stop, charge, etc. 3. Many EVs do not tow. Ignoring #2 and #3, #1 is a killer. If you say "but someone can just rent one", for less than the cost of the rental (probably much less), one could rent an entire car. Isn't that simpler? 7. Aug 14, 2016 ### Algr Billy: The idea only makes sense as a rental. If you need this more than a few days a year, you should buy a hybrid instead. Vanadium: That cost is certainly because those are hand-made one offs, not mass marketed. Stationary gas generators can be had for$400, and ARE light enough to go on a hitch, so adding the mobility can't be that expensive. Of course you DO need to design the car to accept the generator, but current hybrids can charge and drive at once.

Another way to look at my proposal is to imagine a hybrid and make the generator and tank detachable, and rented. So I know in terms of hardware this stuff exists.
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A side question: Do current plug-in hybrids have an issue with gas sitting in the tank for 6 months? This could happen if the user always plugs in and doesn't make long trips.

8. Aug 14, 2016

Staff Emeritus
If you think there's a market, go for it. However, I think you should know that there are 175,000 pure EV cars in the US. If you think that on average the non-Tesla owners need this range extension 3 days a year, you have a total market of about 1000 units. To put that in perspective, Enterprise has three-quarters of a million vehicles.

9. Aug 14, 2016

### Algr

Guh!

You are recreating the whole chicken-and-egg senario that prevents any sort of infrastructure change. In 1910 you could "prove" that air travel could never be mass marketed by siting the lack of airports. That would have been true if the government hadn't invested heavily in planes. (for military use).

10. Aug 14, 2016

### Ketch22

A few years back a start up electric car company, I think it was called a Tango, did something like this. It was essentially a small commuter style car the power usage at standard highway cruise was relatively low. In their introductory tour around the US pulled a trailer. They had a rather small gasoline powered generator (which is of course tuned for highest efficiency at a set speed). The car was full electric however if going long distance one could take a little trailer. It generated power slowly but efficiently and they managed to achieve close to 80 mpg average while touring. Their concept was not a rental thing but a designed special trailer. If you are in town run electricity and skip the engine. If your going to need an engine take it along with you.

11. Aug 14, 2016

Staff Emeritus
I am preventing change? I said if you think this is a market, you should go for it. How is this preventing change? I've provided some facts (and one multiplaction). How is this preventing change?

That said, I would not be likely to use this service. This is based on my exeperiences:
• Owning a PHEV (with 25 miles of all-electric range)
• Driving a trailer
• Renting a car
With my present car, I use 92% less gasoline than my previous car. Heroic efforts to remove that last 8% don't interest me. Put another way, 92% of the benefit I am ever going to get, I have right now.

12. Aug 14, 2016

### Algr

You are personally blocking electric cars, causing global warming, and the Zika virus.

13. Aug 16, 2016

### CWatters

Many families have two cars, having one gas and one electric makes a lot of sense for now.

14. Aug 16, 2016

### Staff: Mentor

A quibble here: for the power needed you are low by a factor of 10.

15. Aug 16, 2016

### Staff: Mentor

Definitely. Next time I buy a car i'll be considering a pure electric and keeping my gas car.

16. Aug 16, 2016

### Algr

Is that peak, or average? Cars always quote peak, but those generators quote sustained power.

In any case, ultimately my proposal is about combatting the range anxiety that lower cost electric cars might face. People seem to dramatically overestimate the problems a car with a 90 mile range might have. Even if gas trailer rental isn't very profitable, their availability could sell lots of electric cars.

Yes, I thought of that. The detail about "your home is in the other direction" was to take the assurance to a higher level.

17. Aug 16, 2016

### Staff: Mentor

Sustained. From Billy's link, you need 20-25 kW, which will run around \$5,000.

18. Aug 16, 2016

### CWatters

Towing a trailer costs quite a lot of energy so you wouldn't want to do it all the time. You would need some enterprising company to make them available to hire and it would probably be one way hire. I can't see any company investing in the infrastructure for this as it will be rendered unnecessary in a few years.

19. Aug 16, 2016

### CWatters

I also wondered how many electric cars can be driven while on charge? I suspect most won't let the car move with the cable connected?

20. Aug 16, 2016

### Algr

"CWatters,

We've addressed those points already. These are rentals. Based on my usage guess you'd need about 1 per 100 electric cars sold. These are for new mass market electrics, not the niche products currently available.