Electric cars, unclean at any speed

[oil pan 4]

Originally Posted by redpoint5

The generator would be run at peak efficiency at all times, and be less complicated/expensive/dangerous than a pusher parallel hybrid.

If you going to use a pusher trailer with auto transmission enough to justify its efficiency over the gen trailer then you might as well just keep the liquid fuel powered car.

Originally Posted by P-hack

I did the math, 10kw @60mph? really? The pusher above gets 25-30mpg on b100 for reference, but it is an auto and lotsa weight in batteries and trailer

Sure why not?
The 10kw coming off the trailer could supply say 80% or 90% of the power to drive the vehicle.
Or god forbid, slow down to 55mph.

[P-hack]

There are significant losses in your typical budget generator, and a charger that can handle the load (rectification, regulation), if one exists for your pack voltage and can handle ~10kw, are probably not super efficient in budget land as well.

I don't know how cheap a 10kw diesel generator and suitable charger are.

plus whatever power you put in the batteries will come at a charge/discharge loss. This is a fundamental compromise in this design, as keeping the generator loaded properly keeps it near its peak efficiency, but the batteries are that load when driving demands are below the generator output. If the generator is 85% efficient at rated load, all power in and out of the battery will be notably less.

And there are losses in the controller.

And losses in the motor (which can be load/rpm sensitive also).

and losses in the existing drivetrain to consider plus trailer/equipment when sizing the generator (and accessories, lights, fans).

But if you only take a few long distance trips then I could see a basic generator and charger helping certainly, the charger might have to be robust, and the generator remotely started/stopped.

In a diesel locomotive the whp is about %85 of the bhp, but bigger is often more efficient too, so I am not sure that figure scales down to 10kw.

[P-hack]

but if you actually measure your hp demands at a given speed (say 55) and choose an engine that is just the right size and sprocket it to a clutch and wheel, you are looking at maybe %98 transmission efficiency, the battery/motor can smooth out the fluxuations in power demands. And you have an efficient hiway assist, a sequential gearbox with air (or solenoid) shifter could be controlled remotely too.

And if your car supports regen it can even load the engine while driving if the charging the batteries for efficiency strategy even works out (TBD). Though pulse and glide would be better.

[oil pan 4]

I would not recomend trying something like this with a budget generator.
They are very noisy, make lots of vibrations, suck down fuel as if there were a hole in the fuel tank and they tend to have short lives before encountering their first problem (100 to 500 hours).

A 4 pole generator would have to be used (1800 RPM) to get the engine to run fairly quiet and to get fuel consumption down to acceptable levels. These 4 pole generators tend to have very long life due to much lower vibration I think.

For a gas engine you would need something like a 20hp kolher V-twin, that way you can get the 12hp or so you need to drive the generator down at lower speed (1800 RPM).
For a diesel a smallish >1L 3cyl kubota diesel would work. Add a turbocharger and get an additional 10% more fuel economy.

A 3phase generator would further reduce engine load. I was reading that a 3phase generator takes about 12% less engine torque to turn than a single phase putting out the same load.
Plus 3phase makes much better DC power than single phase with out a lot of other stuff.

[P-hack]

Probably a diesel rabbit front clip with an auto would be pretty cheap (thinking I could do it for $1000ish) and gives mileage similiar to your estimates using a regular (and epa "approved") engine/drivetrain and minimal engineering. And there is obviously a LOT of room for improvement there using a stick shift and technique and a downsized engine. Just saying. You can't pulse and glide a genset very efficiently.

[NachtRitter]

Probably a crazy thought... but I wonder if you had an arrangement similar to Sharkey's (EV with diesel pusher for long trips), if it would be possible to use it similar to some hybrids ... use the EV only for portions of the trip and then when the battery gets low (or when the speeds are higher), fire up the pusher to not only push, but also (potentially with a heavier duty alternator) provide a charge to the EV (via umbilical). Obviously that will add load to the pusher engine thereby reducing the pusher FE, but there'd definitely be excess capacity on the pusher engine (especially when at cruising speed). Plus the combo of EV and pusher use should still give some pretty magical FE numbers, as they do with the Volt and similar hybrid vehicles.

EDIT: I'm assuming here that recharging the EV by engaging regen and having the pusher "overcome" the resistance to forward motion would be much less efficient than recharging the EV directly from the pusher alternator... though admittedly I don't know if any alternator could provide enough juice to recharge an EV's pack in any reasonable amount of time...

[P-hack]

If your controller has regen you can use that to recharge the batteries (light braking) while the pusher is pushing you. Though most hybrid MPG champions avoid recharging the batteries with gasoline alltogether.

[P-hack]

and of course it would be desirable to have an energy management strategy as you approach your destination so that you can deplete your batteries and then recharge them from the wall instead of fuel.

[NachtRitter]

For the usage I had in mind (when I posted my "crazy thought"), the goal would not be to get "MPG Champion-level" FE, but rather to be able to cover long distances (obviously exceeding the range of the EV itself) while still getting "better than average" FE. The idea being that once at the destination, the pusher is parked and the pure EV can be used for local travel (and can be recharged using local resources). In my case, I typically travel to parents about 1000 miles away once a year, so I can relate to this kind of scenario.

Probably using regen to recharge the batteries "in-flight" is a lot less complicated than doing the "larger alternator" etc. Especially if that's already an existing feature of the EV.

I also realize that simply buying something like the Volt which accomplishes essentially the same thing would be a lot simpler too... just that the thought of a brilliantly executed DIY solution which outperforms anything available commercially is rather appealing...

[P-hack]

The volt is ridiculous But a $1000 trailer that you can hypermile should give excellent results, like 40+mpg, which IS better than the volt. Though you will be busy driving 1.5 cars (sounds kinda fun to me).