A 100kW generator would be huge and incredibly inefficient.... you'd get much better performance using the gas/diesel to drive the wheels directly.Here is the basic idea. It will be a series hybrid type. Small V6 gas or diesel engine (leaning toward gas for convenience) mated to a generator (alternator) right at the flywheel. Then a large electric motor to power the drive wheels. The generator would have to be large enough to charge the batteries and power the vehicle; so my rough math says around 75-100 kw minimum.
While far short of the efficiency of a mechanical transmission, I don't know if "incredibly inefficient" is an appropriate term.A 100kW generator would be huge and incredibly inefficient...
I think that either they will "camp" at serviced (with power) sites, or they will run the generator, because even a 100 kWh battery is unlikely to be sufficient for a return trip (not just one way) plus power for duration of the stay.... I have a colleague who is working on an electric RV. They are using two 'small' Tesla motors (FWD) and a complete Tesla battery pack. They are also using the BMW i3 REx (~20kW) for emergency range extension. They estimate electric only range at more than 250 miles using the Tesla 100kWh battery and said they will rarely drive beyond the battery range in a single day... it will be interesting to see if the REx is ever installed![]()
For the generator, the largest EV motors (even the new-for-2018 Leaf) should be suitable for continuous output at the desired level (up to 100 kW).... The thing I am having a hard time finding is a genset for the engine that doesn't weigh a ton. TM4 makes a bunch of different units that are made for busses or small commercial vehicles, but they don't sell to the general public.
Anybody know where I can find something like that? I'm considering the Model S drive unit because it has been hacked already, and the power/torque is appropriate for my size vehicle.
The people in question regularly travel across Europe where power is widely available both at rapid chargers and at camp sites. They kept a daily log last year when they traveled from UK to Greece and back over a six week period, at no point would an RV with a 250 mile range have been a problem for themI think that either they will "camp" at serviced (with power) sites, or they will run the generator, because even a 100 kWh battery is unlikely to be sufficient for a return trip (not just one way) plus power for duration of the stay.
I agree and my colleagues have chosen 'small' Tesla drive units because the overall package is so smallFor the drive motor, I think the solution is multiple motors, at least one per drive axle, to avoid the need for a single high-power motor. That could be an entire Tesla or Leaf drive unit at each axle.
So it's the first of my two options. Glad that works for them.The people in question regularly travel across Europe where power is widely available both at rapid chargers and at camp sites.
I'm still young enough to drive more than that daily.....for now.A 100kW generator would be huge and incredibly inefficient.... you'd get much better performance using the gas/diesel to drive the wheels directly.
That said, I have a colleague who is working on an electric RV. They are using two 'small' Tesla motors (FWD) and a complete Tesla battery pack. They are also using the BMW i3 REx (~20kW) for emergency range extension. They estimate electric only range at more than 250 miles using the Tesla 100kWh battery and said they will rarely drive beyond the battery range in a single day... it will be interesting to see if the REx is ever installed![]()
I'll give up a little efficiency for better packaging. If my RV was electric with a range extender, I could ditch the onboard small gas generator for 110v, which is one more thing to maintain, and it would open up some storage space.The good news:
- The idea can certainly work - there are many series hybrid buses on the road to prove that this powertrain configuration can work for this size of vehicle.
- Having a large battery pack and a good (quiet, efficient) generator in an RV is obviously a good thing.
- If you only need 100 kW, it doesn't even need to be a V6 engine.
Now the issues:
- Hybrids get their efficiency advantage in stop-and-go urban traffic, but RVs spend most of their driving time cruising highways; the inefficiency of turning mechanical energy into electricity then back into mechanical energy is a problem.
- The biggest performance challenge for an RV is typically climbing mountain highway grades at high speed; even people who live in flat areas tend to go to mountainous areas for recreation. That means that the vehicle must sustain high power for a long climb, which is exactly the wrong situation for a hybrid - high electric motor power and large battery capacity are required.
Of course nothing is ever that simple. The RV won't see urban use, but there would be some (small) advantage of the hybrid system during regenerative braking on mountain descents. Climbing grades might be viable; for instance, a 24 kWh (Leaf or whatever) battery adding 80 kW (Leaf continuous power rating) to 100 kW of generator output might be enough, and could be sustained for 10 minutes.
This particular RV is not completely like a barn door, but it is heavy. Maybe two smaller motors would be better. Can modern controllers sync two motors accurately?For the generator, the largest EV motors (even the new-for-2018 Leaf) should be suitable for continuous output at the desired level (up to 100 kW).
For the drive motor, I think the solution is multiple motors, at least one per drive axle, to avoid the need for a single high-power motor. That could be an entire Tesla or Leaf drive unit at each axle.
I doubt that any of the Tesla Model S/X motors are actually suitable as a single motor for the motorhome, because the heavy vehicle with barn-door aerodynamics will require substantially higher continuous power than the less massive and much sleeker Tesla car. Under continuous heavy load, the motor is likely to overheat... and the Tesla-powered Cobra race car people have discovered.
They can 'easily' drive 500 miles in a day with a single charging stop (for lunch?)... they could use the ~20kW REx for charging but in reality I think they'll just use the public charging infrastructure because it's faster and a lot cheaper than petrol/gasI'm still young enough to drive more than that daily.....for now.
Again, good for them.They can 'easily' drive 500 miles in a day with a single charging stop (for lunch?)... they could use the ~20kW REx for charging but in reality I think they'll just use the public charging infrastructure because it's faster and a lot cheaper than petrol/gas![]()
Do you mind sharing the make and model, or at least the size and type (length and Class A, B, or C) of the RV? It would help provide context.This particular RV is not completely like a barn door, but it is heavy.
Yes, EV manufacturers have no difficulty coordinating two motors on separate axles; they even run two motors on the same axle (one for each wheel) in some hybrids and some limited production EVs. It's not difficult for the technology, but I don't think that off-the-shelf controllers for DIY builders typically have control logic to handle this... although I may be mistaken. Not many DIY builders use more than one motor.Maybe two smaller motors would be better. Can modern controllers sync two motors accurately?
It does not matter, since you command torque, not speed.I don't think that off-the-shelf controllers for DIY builders typically have control logic to handle this... although I may be mistaken. Not many DIY builders use more than one motor.
I was trying to keep the Make and Model under the radar, but it will be in a classic mid-70's GMC Motorhome. They are front wheel drive based on the Oldsmobile Toranado package. The transmission basically wraps around the left side of the engine and then it is directly mated to a differential (final drive). That is one of the reasons for looking at electric motors. Nobody makes a transmission quite like the original TH425 that can handle the weight of a 10,000 lb motorhome. Unfortunately, without something really new and unique, they are stuck with the big block Oldsmobile 455 with a 3 speed and no overdrive.Do you mind sharing the make and model, or at least the size and type (length and Class A, B, or C) of the RV? It would help provide context.
Also, I've been guessing that "UND_Sioux" refers to the University of North Dakota, and that school's traditional name for its sports teams. That would place the likely location for the use of this RV in North Dakota. Is that correct?
Assuming that this is your Solectria E-10 pickup, this is the easiest case of the motors driving the same shaft (to the rear axle in this case):It does not matter, since you command torque, not speed.
Each motor will output the desired torque, independent of each other.
My truck has two motors and two controllers, and they don't talk to each other at all.
Each one takes in a throttle signal from a dual gang pot.
You could connect two motors together, driving the same shaft.
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Coordination of the two is easy, because they will always run at the same speed.