While the top speed of the electric motor limits it to about 40 mph with the ICE off, a larger capacity battery can (if I understand the response I recieved from Hymotion) and will provide significantly improved economy at speeds over 40 mph.

Essentially, as some of you already know, the eCVT is really just a planetary differential between the EV and ICE drives. The EV system regulates the speed of the ICE whenever it is running by simply adjusting rpm to put the ICE into the desired torque range.

A larger battery, and probably some software hacking, would allow the EV side of things to spin faster at speed, keeping ICE rpms low and improving overall economy. This in a nutshell is what helps the FEH achieve best ICE-on economy around mid-40 mph, as the ICE runs at a low 1500 rpm or so while the electric system takes up the slack.

Having the extra juice of a larger battery pack and the programming to match, the same 1500 rpm could conceivably be maintained at 70 mph, providing as much as 70 mpg on the highway. (At least until the battery runs out. )

 

The FEH can run off "battery power" at any speed. I hope this does not confuse people, but I have propeled my vehicle forward, with forward acceleration using the battery pack only, at speeds of 75MPH many, many times.

( You all probably have also without knowing... )

But yes, the ICE has been spinning also, as you say, at a lower RPM ( 1500 to 2200 ) to help moderate the overall speed of the eCVT.

It is more correct to say I guess, that the FEH can only run up to 40 MPH with the ICE not spinning.

It is correct to say the FEH can run solely off battery power at any speed.
It can, and does, such as going downhill, or over level ground with little load.

My best tanks were at highway speeds, with ICE on, with hilly terrain.

 

I have no knowledge of mechanical engineering, so please forgive me for the dumb question:

So that means, that if we gave the FEH a much bigger battery, and tweak the firmware, the FEH can conceivablybe a pure EV (at least 95% of driving conditions)? Is the only restriction for the FEH to go only up to 40MPH without ICE is the battery (acceleration performance not withstading)?

I hope this is the case, as I would really like to keep my car for 15+ years until battery technology is cheap and good enough to do this.

 

The car under EV can only be DRIVEN to about 40MPH. To go faster the ICE must turn on and provide power because the electric motor can only turn fast enough to move the vehicle at 40MPH. If, however you are rolling downhill, what the earlier poster is saying the ICE will have to come on (because the electric motor is limited as to what RPM it can turn) but no gas is needed for the ICE (no power is required). The driveshaft and engine can just rotate fast enough to make up the difference as the vehicles weight pulls it down the hill faster than 40MPH.

Which I don't know for sure, but it does make some sense to me.

 

To avoid overspeed of the electric motors, the engine must come on at 40MPH.
When the engine is spinning, the electric motors can slow down. But they can still contribute torque to the wheels, even at 95 MPH.

As speed increses, torque decreases with any electric motor.
Above 40 MPH, there would not be enough torque to start the ICE when you did want it, at say, 50 MPH. So it must come on at 40 MPH, "just in case".

If I'm going downhill by gravity at 65 MPH, and I want to accelerate to 70 MPH, I need very little torque to do so. This small additional torque, to increse speed by 5mph is often provided by the electric motor. The gas engine is spinning to allow the motors to operate in a safe range of RPM, but no additional gasoline is burnt for me to accelerate in this case. My acceleration is "pure electric" at 65 MPH.

Another way to look at it. You have pump that can pump 40 gallons per minute, and a pump that can pump 100 gallons per minute.

The 40 gallon pump is your electric motor. The 100 gallon pump is the gas engine.

If you need between 1 and 40 gallons per minute, the electric pump can do all the work. As soon as you need 41 gallons per minute, the gas pump MUST come on. There is no way around it. The gas pump has a minimum rate of 40 GPM. Thus, at this point, the electric pump drops to 1 GPM. Follow?

If you need 65 gallons per minute ( or 65 MPH ) the gas pump can go 50 GPM and the electric pump can go to 15 GPM. Now... I want 70 vs. 65. The gas pump ( gas engine ) can stay steady at 50, and the electric can boost up to 20.

The electric motor is really staying under that 40 limit the whole time, but is "helping" you go from 65 to 70, or any speed in between.

Make Sense?

This is what I was saying 2 posts down. Battery size has nothing to do with it.
A larger battery would give you more miles under 40 MPH, but never allow you to go over 40 MPH without the engine on. There is no "hack" around this, without severe damage to the vehicle.

 

Thanks, John, for the analogy. Makes perfet sense. I understand a lot more now.

..But...(and again please indulge my ignorance)

From what you described, the FEH cannot go faster than 40mph via emotor only without some external power (whether ICE or via the axels [power from going downhill]), then there must be a "mechanical" limitation - i.e. the emotor spins out of its bearings, or the planetary gear system grinds to a halt.
OR
Is that limitation a "power" limitation - per your "torque" motor requirement to start the ICE?

It seems to me that the planetary gear system (again, out of ignorance here) is integrated to give the FEH any speed (up to vehicle top speed), whether via ICE or motor (or roling down a hill). As you said, the requiremt for the ICE to come on is to limit the emotor to a safe RPM. It is therefore the emotor that is the limiting factor -- whether for torque requirement (to start the ice), or mechanical (melts the bearing), or some power requirement - not enough juice from the battery. Or a combination of all three (and prob some other limitations I wouldnt even start to imagine).

This discussion doesnt have to go any further...it may be just my own wishful thinking along the line that if the limitation is power only, then simple battery replacement is fine. If the motor is the limit, then a harder thing to do (but possibly doable) is a larger motor. If it's the gearing system...

 

In short, it's for all the reasons listed below. Battery power being the LEAST limiting. Again, more battery = more distance under 40 MPH. Not more speed.

 

Sorry, but instead of starting a separate thread, I thought I would ask this here.

When the ICE is spinning, but not using any fuel, does the tach show its actual RPM, or does the tach still sit at the battery icon since the vehicle actually being propelled by just the electric motor?

 

From memory I believe the tach shows RPM. The engine is officially turning and I don't think the tach can tell fuel flow. Its very unlikely the tach is hooked to the computer to even know about fuel flow or anything... its just hooked like a normal tach and measuring revolutions. If you have a NAV there shouldn't be any arrows coming OUT of the Engine symbol. There might be one going IN from the motor.