Tim, it is my understanding that both motors and the engine can be used to propel the vehicle forward. The large traction motor is used for reverse mode and the small generator/motor is used to start the engine. Both motors can generate energy, but the large traction motor is used to capture regen braking energy from the wheels only when you let off the gas pedal in "Drive" or "L" or hit the brake pedal.

There is no regen braking in neutral, but the small generator can generate power with the engine in active neutral (over 6mph). Under 6mph, the small generator/motor does not charge the battery or provide energy to the converter.

Hope this helps.

GaryG

 

I always thought the ICE was powering the generator and that generated electricity was sent to the traction motor in hybrid drive mode. If both the generator and the traction motor were ever powering the drive wheels together it would drain the battery pretty fast and it wouldn't make a whole lot of sense. The battery already doesn't fully power the traction motor because it can't produce enough current to run it at capacity. In reverse you are moving with only the traction motor. If you need extra power however the ICE will come on to give you extra current through the generator that goes to the motor.... If the battery can't provide enough current to push the motor full strength, why would you kick on the ICE to produce more? what would be the point of adding the generator/motor to pull even more current from the battery that clearly couldn't fully power the traction motor already trying to move the vehicle.

When you are going down the freeway it seems pretty clear that the engine is powering the drive wheels and sending some power to the generator that makes electricity for the traction motor that is also powering the wheels. This split path is how the system "shifts" lower "gears" send more power through the traction motor (with its higher low end torque), higher "gears" send more power from the engine directly to the wheels and less through the traction motor (its an oversimplified explanation to be sure).

I don't believe the generator/motor is ever used to push the vehicle directly. The ICE can send power to the wheels and so can the traction motor, but the generator is only used to make electricity and to start the engine is what I understand. I could be wrong but you can see above my reasoning for that belief.

 

TeeSter - "I always thought the ICE was powering the generator and that generated electricity was sent to the traction motor in hybrid drive mode."

Tim, not sure what you mean by hybrid drive mode, EV? The small motor generator can provide both electric power to the traction motor and to the HV battery for storage.

TeeSter - "If both the generator and the traction motor were ever powering the drive wheels together it would drain the battery pretty fast and it wouldn't make a whole lot of sense. The battery already doesn't fully power the traction motor because it can't produce enough current to run it at capacity. "

In electric mode, torque is supplied by the HV battery only. The torque is supplied to the output shafts by the traction motor, the generator motor, or a combination of both. It does drain the HV battery pretty fast but this is the preferred mode whenever the desired torque is low and because the electrical system rather than the engine is more efficient.

The small generator does not provide torque to the output shaft in any other mode accept EV.

TeeSter - "In reverse you are moving with only the traction motor. If you need extra power however the ICE will come on to give you extra current through the generator that goes to the motor.... If the battery can't provide enough current to push the motor full strength, why would you kick on the ICE to produce more? what would be the point of adding the generator/motor to pull even more current from the battery that clearly couldn't fully power the traction motor already trying to move the vehicle."

In reverse, both motors can operate in the reverse direction in EV mode. If the battery needs to be charged, the sm generator can provide power to the traction motor in reverse or charge the HV battery or a combination of both with the engine driving it as a generator. As far as power demand in reverse, that depends on the controllers and the SOC of the battery.

GaryG

 

You're going to have to find a reference somewhere to convince me that the generator is ever used to apply torque to the wheels. I just don't see the point.

In other posts its clear that in reverse the ICE has to come on to provide enough current to max out the traction motor if you are going up a big enough hill (that has been discussed elsewhere on this group)

This leads to conclusion #1. The battery alone cannot provide enough current to drive the traction motor to its full rating. Its current is limited by the battery output even at full charge.

That leads to #2. In reverse in EV (battery mode) If I don't have enough current to drive the traction motor to capacity it doesn't make sense to send battery current to the generator motor, I'm not going to get extra power that way the problem is I don't have enough current. I have plenty of horsepower or torque in the traction motor but I can't access it because the traction motor isn't going full power anyway. Instead the engine kicks on, turns the generator and that current supplements the current from the battery to turn the traction motor at its full power rating.

Hybrid mode I'm using loosely to refer to when both the engine is on AND the traction motor is driving as well. Usually in that mode the ICE is also powering the generator and sending current to the traction motor at freeway speed. On the NAV unit its referred to as HYBRID DRIVE.

 

There are several "hybrid" modes. There are also a nearly infinite number of ways to send torque to the wheels.

Yes, I can confirm that BOTH motors CAN provide torque to the wheels when certain conditions are met.

It is preferred for the larger traction motor to provide all the torque to the wheels, but there are certain speed / RPM conditions when the smaller starter motor can contribute torque to the wheels.
-John

 

I'd be more than happy to point out my Ref. point Tim.

Section 1-74 of the PCM/ED of the '05 FEH workshop manual - Electric Mode: "The hybrid electric system operates in the electric mode when the vehicle is propelled by the electrical power stored in the high voltage traction battery. The torque is supplied to the output shafts by the traction motor, the generator motor, or a combination of both. This is a preferred mode whenever the desired torque is low and the electrical system rather than the engine can produce it more efficiently. The electric mode is also used in reverse because the engine can only deliver torque in a forward direction." Complete paragraph word for word Tim.

Your confusing the max current and torque of the traction motor, which I only addressed to say the controllers and the SoC of the HV battery determine for max torque. This may require the sm generator motor to change to the charging mode to supply current directly to the traction motor, I never disagreed with you on that.

In the positive split mode or the negative split mode, I don't see the sm generator contributing torque to the drive wheels, but if GPSman can give me a REF., I'll look at it also.

GaryG

 

Keep it up. I'm learning a lot from this

 

Thats why I said you'd have to find a reference to convince me. Because if you were right I knew you'd have one. I knew I could be wrong--but I'd have to be convinced becuase on the face of it, it didn't make alot of sense to me.

Hmmmm.... I guess the truth is they probably did more optimizing than even I was expecting. With the planetary gearset nothing STOPS you from using both motors to drive the vehicle. The question is what advantage that gets you if the traction motor needs more current anyway. I would guess that each motor--because they are differen't sizes--will have its own torque curve (so does the ICE) that relates the torque produced vs the amount of power used in producing it. And in some cases the most efficient way to produce a certain amount of torque in EV mode must come with both motors driving, rather than just using the traction motor and adding more current. Essentially the efficiency of the traction motor begins to fall off near its top end and running the smaller generator motor in a better part of its working range is better.

 

That's funny because I think the same way John (GPSman) regarding the use of the sm generator assisting torque to the wheels in the positive split mode, but I can't find a clear ref. if someone like you wants to know where I got the information. But by all means, call me and others on these things. We've all seen incorrect information being passed around and it's better to get it corrected ASAP, or it begins to snowball.

Notice that in electric mode, you may only need the sm generator motor to back you out of a parking space to save energy. The ref. said either or both motors! That's why I stated it's up to the controllers and battery SoC.

bg1811, when I first got my '05 FEH, very little was known about it or the techniques that can be used to hypermile the FEH. Today, I think a 42mpg tank is just terrible for me. If I were to move up north in the cold, I don't know how I'd rig my FEH so I wouldn't go crazy. If any of you have not read my article on "Hypermiling The Ford Escape Hybrid" and the 80 comments and questions to that article, it might be helpful. I just got my wife a nice Sony high definition handycam (HDR-SR1) for Christmas and we plan to add a video of how I drive using these techniques in that article. It's very hard to explain just how to nail down a 70mpg segment in writing, so we thought a video would help. Here is the link: http://www.cleanmpg.com/forums/showthread.php?t=350

GaryG

 

And what if the traction motor is too hot, or out of service for some other reason? There may be conditions not normally thought of when the smaller starter motor may be able to contribute to propulsion.

I'm not saying this is the case... I havn't tried it... but what if the traction motor was broken? Could the starter motor back you out of a parking stall?
I think yes it can... and may be a primary purpose of the "one-way clutch".
I'm going to have to think about this senario for a while....

-John