Tow a generator from that towbar

Tow a generator from that towbar

Range anxiety could be a thing of the past if you towed a trailer around the world. You could put all your luggage in, a generator, drum of gas, dogs, surfboards, what have you. Game over. Maybe Elon could divert some cute designs from the tube project, make little road trains.

I wonder what would be a minimum size generator to produce constant power and never run out? Forgetting about superchargers. Where I come from there aren't any, but there are plenty of trailers...

grant10k | 12 augustus 2015

You can't charge while moving, but some of the bigger generators output 220v, so you wouldn't be stuck on the side of the road for too long.

I looked at some of the generator's max sustained output and fuel capacity and it turns out, you can get a pretty good MPG charging a Model S from a generator (in theory). Better than most non-hybrids.

It's just a thought experiment, and I hadn't tried it, but if it's true, I'd imagine the good fuel economy comes from the fact that all the output from the generator is used so even with the conversion losses, there isn't any additional waste beyond that. wouldn't need constant power. Just something that starts the generator when you're at a quarter tank of electrons, and fill it up until you're at 3 quarters of a tank. No need to leave it on forever and waste fuel.

eric.zucker | 13 augustus 2015

That would seem very counter-productive. First the whole point of EV is to get rid of fossil fuel, so that defeats the mere purpose of a Tesla. There are plenty of ICE powered vehicles available if you want to burn fuel and move around.

Think about it - Imagine the Tesla MX has a range of say 300 miles (wishful thinking!). Takes 5 hours to drive this far on the highway. Car battery capacity is 90 kWh, over 5 hours, means we use 18kW par hour on average. Driving faster or going uphill it's way higher, up to around 550kW with full Ludicrous output.

Practically you would need to haul a 20 to 25kW generator to deliver anywhere near the average current you're using while driving. We're in luck, with dual chargers we can feed 22kW into the battery.

But - hauling the generator will cause you to use more power. we're talking an extra 3000 lbs at least behind the MX, just the generator on wheels, no luggage, and no fuel tank.

I have generators parked right outside my office, all sizes from 5kVA to 800kVA (Volt-amps are more or less equivalent to watts, depending on the power factor of the load).

Now the real killer ... Once you figure out the amortization of the generator, fuel cost, and maintenance, the energy will cost you somewhere between 20 to 50 times the cost from the grid. The only reason they exist is when someone needs power in a hurry when the grid is too far or not able to supply as much power as needed.

Ankit Mishra | 13 augustus 2015

Great things take time. Meddling with them in order to cut time beyond a certain limit damages the whole initiative. Charging infrastructure will get better. Please have patience.

doctoxics | 13 augustus 2015

Future thought: include a 90 kwh battery pack in whatever you are towing.

adamgreen | 13 augustus 2015

For what it's worth, a Honda 1000w (30lbs) or 2000w (45lbs) generator is easily carried in one hand like a (heavy) bag. A pair of them can be connected in parallel by a factory accessory to produce 240V 30 amps. I have this setup and have used it for 5+ years. That's 30 kWh per gallon (round figures, I don't purport to be a chemical engineer) so perhaps 15-30% increase in range. I then carry an additional 2 gallons, so each generator can be fully refueled once.
These generators are $1000 each, plus the kit, so it's hardly a clever cost saving device, but I have no qualms about putting them on an aluminum tray suspended from the hitch (no wheels) behind an (electric) motorcycle carrier, and giving myself a helluva nice way to go roaming around the mountains with zero range anxiety.
I have to accept the guilt of the emissions, plus say a 2 gallon gasoline bomb sitting in a protective enclosure outside the vehicle ... still far less irresponsible that the way I've done this for years in the past, speaking glass half full. Some say the electricity arriving at a typical California home or supercharger is hardly zero emissions.
My only real "range anxiety" for the Tesla is getting stuck on i80 during a blizzard in 50 miles of bumper-to-bumper traffic at a standstill for four hours while the car endures zero degree wind chill. : |

vandacca | 13 augustus 2015

@adamgreen, the nice thing about being stuck at nearly a standstill is that you won't be using much battery. The slower you drive, the better range you will get, which should help to offset the loss of range due to the cold weather. :)

eric.zucker | 13 augustus 2015

@adamgreen something doesn't compute: 240V x 30 A is 7.2 kW. Two 2 kW generators give 4kW.
You can get 115V 30A ( 3250W) In parallel, or 230V 16A with both sets synchronized in series.

aljjr2 | 13 augustus 2015

Isn't this called a Chevy VOLT... electric drive with a gas generator???

Bikezion | 14 augustus 2015

Those (toy) Honda generators are max watts, the 1000w one has a hard time powering my rc charger, to charge the lipo on my kids toy electric motorcycle. At best its like a standard household outlet, about 4 miles of range per hour (for the 2000w model).
The fuel efficiency of a generator at max watts goes out the window. Not to mention the noise and smell.

Roamer@AZ USA | 15 augustus 2015

+1 aljjr2.

Why would you tow a generator and stop to wait while the generator charges the car when you can just buy a car with an engine and not need to stop to charge.

Roamer@AZ USA | 15 augustus 2015

Also better be a very large generator. Most portable generators would melt down delivering constant steady state high amp loads for hours long periods of time. Not to mention the fuel consumption under those conditions would be extremely high.

grant10k | 15 augustus 2015

Roamer, this is all hypothetical anyway.

To answer your questions seriously though, a detachable generator is much more attractive to me than a car with a engine/generator permanently installed. I get the appeal of a plug in hybrid, but to me that sort of defeats the point. 'Battery powers motor' is made an order of magnitude less reliable when you add timing belts and pistons.

Plus if this generator breaks down, an engine swap involves a cotter pin, instead of an engine hoist. And you can still drive the car while you futz with the generator (not at the same time, for safety reasons (unless autopilot gets way better)).

For a Volt with 40mi range, including the generator makes perfect sense, but for a Tesla with 200mi range, the only time it would need to be gas powered would be a biennial trip to the arctic, or whatever popular vacation spot doesn't have electricity.

eric.zucker | 15 augustus 2015

I will get the CHAdeMO adapter, that should give me 40-50 kW DC charging in many places which don't have Superchargers.

If you really want to haul a gen... This one below is equipped with a light mast, but gives you an idea of size...

About 8kW output, 32A @ 230V single phase.

Parking with a trailer is a nightmare... Need two consecutive parking spots. Have fun.

DTsea | 15 augustus 2015

The energy content of a gallon of gas is about 37 kwh and there is no IC engine in the world that can operate efficiently enough to get 30 kwh of useful work from one gallon of gas. More like a third of that.

Ross1 | 15 augustus 2015

Mmmm. No one much likes the idea of a trailer. But for people like me who live in a land with no superchargers but love the modernity and features of a Tesla, perhaps someone should design a Model X with its own internal combustion engine. Looks like plenty of room in the frunk...maybe take it to the Rod and Custom guys.

A journalist brought an S to this island state, Tasmania (where there are possibly just 2 Model S) and had to get it towed back to the ship with a flat battery...

There are many places in Australia with say 1000 miles between power sources. A Tesla owner going bush could have his cake and eat it too if he took along a small generator. We actually call them kilometers. 1000 m = 1600 km.

DTsea | 15 augustus 2015

1000 miles us 1600 km.

1000m is 1 km.
Since brian isnt here.

Seriously an ice in a model x? Bite tongue.

Ross1 | 15 augustus 2015
ian | 15 augustus 2015

Tasmania doesn't look that big. Three or four Superchargers should cover it. Get on the horn to some local business owners and connect them with Tesla. I'm sure they'd throw in a dozen or so HPWC's for the overnight stays too.

Ross1 | 16 augustus 2015

Thanks Ian t, I sent it on to a Tesla S owner who owns the largest tourist venue in Tasmania; check it out.

eric.zucker | 16 augustus 2015

It just dawned on me... Why didn't we think of it before? It's clear now!

The model X will come with a retractable arm and hook, to grab vehicles in front of you, and using regen, charge up en route while traveling!

There you go siphon off 60kwh from any truck, SUV, whatever, and when your battery is full smoke him in the dust, find another tractor trailer to hook onto.

Problem solved.

jjs | 16 augustus 2015

@eric You are a genius! And I think it gets even better. Once attached when you open the Falcon Wings you start to para-fail, or Falcon-sail or something like that! ;) | 16 augustus 2015

Push down spam

milesbb | 17 augustus 2015

You do not make a competitive electric car by modifying an ICE. You do not make a competitive generator aux by using off the shelf generators, and a trailer from Home Depot. If this were to be done the the generator would need to be built to supply constant power of about 10-15 kw DC. Most generators today care little about weight and have a goal to provide power over a range of loads at a fixed frequency of 50 or 60 hz. Tesla would need to buy in on the project and provide connections and controls that could allow charging during travel. A generator that was designed to provide constant DC power with efficiency and weight as design goals would be a much better fit for this use.

Although too heavy to carry on a standard trailer hitch Tesla could add additional support points so that the aux power unit could be carried off the back and fit into the car aerodynamics.

12 kw running while traveling would double the range at 60 mph. 12 KW running while you park would give you a full battery in 6 hr.

A very nice aux power unit could be built to supplement either the MS or MX. However like the battery swap I believe the market wouldn't make this product successful, this unit will not be built,

eric.zucker | 17 augustus 2015

Here is a 18kVA generator on a trailer, which will run continuously, well until it runs out of fuel:

The largest part in a generator is the power plant. Then comes the fuel storage, the alternator is heavy but relatively compact. AC or DC output is not much different.

Sure one can minimize the size and weight of the engine. Here is one of the best power-to-weight ratio Turbine engines which can generate up to 600 continuous HP or 450kW. This uses about 211 kg of fuel per hour.

Assume you created a smaller scale model to produce 15-20kW, that would still use 7-10kg per hour or 9-14 liters per hour. to fully recharge a 90kWh battery needs - in theory - 4 to 6 hours, you need at least a 60 liter tank just for one full charge.

Then you have to deal with engine and exhaust temperature and noise issues. Kerosene is not too different to diesel fuel, and should not be too hard to find. Add maintenance costs each time you fire up the turbine engine and you'll understand why helicopter flights are so expensive.

I for one will keep my MX purely electric and charge at home, then Supercharge or CHAdeMO charge on longer trips.

Boredwithnames | 18 augustus 2015


Seen a mock up picture somewhere of a Battery Trailer, its smallish with the bottom half a battery and the top half an enclosed trailer.

Seems quite an interesting idea - gives you extra range like a spare fuel tank on a fighter jet and also more storage for a tent etc.

eric.zucker | 18 augustus 2015

Balancing the external and internal batteries is not trivial at all. When one is nearly empty and you connect the other one fully charged, the initial balancing current will be huge and damage lithium ion cells.

Assuming this was manageable, it would require flexible cables between the car and trailer capable of bearing very high currents (several hundreds of Amps), suitable connectors, and lots of safety features to disconnect both ends electrically and mechanically if there is an accident to prevent hazard (electrocution, fire).

I'm not saying it can't be done, just that it should be done carefully. The idea especially makes sense using two supercharger connections, one for the Tesla and another for the PowerTrailer. Then you could really benefit from the increased range and not impact recharge time.

Lots of effort, and I think Tesla has enough on their hands at the moment. I'd rather see them increase the Supercharger network density, expand it to cover more areas, and deliver both Model X and Model 3.

vandacca | 18 augustus 2015

Towing a gas/diesel generator is what happens when a redneck buys a Tesla... :-)

And towing a bigger battery is not the solution either and it never will be. An external battery will never have the same efficiencies as the existing internal battery, so it will never be worth it. How many people here drive their ICE vehicles with a gerry can full of gas? Consider that it is infinitely less efficient to do it with batteries.

An external trailer with batteries will have to have additional cooling/heating to protect the batteries. It would also have additional protection (titanium plates?) to protect it in case of a crash or hitting debris on the road (because we wouldn't want it to catch fire and loose our big investment). This will add significantly to the weight of the vehicle and hence reduce the extra range that the batteries will provide. Further reducing range is the aerodynamic hit of towing this trailer.

When everything is said and done, you'll be paying thousands (or hundreds of thousands) of dollars for a device that will give you a few dozen more miles in range. The numbers don't work.

The problem will solve itself with more efficient batteries and a better charging network.