Obviously the front wheel drive Escape Hybrid does braking regeneration only through the front wheels. Unless I'm mistaken, I believe this is true also for the awd version.

When braking is done only using regeneration, then the fwd or the awd should recapture all the energy available. Some braking is a combination of regeneration and using the mechanical brakes. All braking done with the mechanical brakes uses mostly the front brakes, but, depending on the circumstances, a varying amount is done with the rear brakes. It seems logical that all braking done with the rear brakes is energy lost to regeneration.

The awd model has a mechanism available to regenerate with the rear wheels. All it has to do is engage the clutch/solenoid system in the rear axle, which would turn the driveshaft, send torque through the Power Transfer Unit into the eCVT, which turns the generator and so stores power in the traction battery. I guess the simple question is whether the Active Torque Coupling in the rear axle is engaged during regenerative braking.

So far as I know, it does not do this. It may be mechanically impossible, maybe related to the fact the engine cannot deliver torque to the wheels in reverse.

This leads to a concern that if regeneration is done with the front wheels only, in situations where braking is being done with regeneration alone and not the mechanical brakes, this amounts to braking with the front wheels only. This is an unstable configuration that could result in loss of control on slippery surfaces. It seems to me I've read that this would cause activation of the ABS system and in turn that switches braking from regeneration to the mechanical brakes. But it would be better to avoid this sequence in the first place.

There's no way around it in the fwd version (unless you waste some of the energy available by partially energizing the rear mechanical brakes). But in the awd version, some of the regen braking could be done by the rear wheels without wasting energy if the rear wheels could be included in the regeneration layout by using the awd components. This is all the more important because braking tends to be done entirely with regeneration only during less severe braking where there is less weight transfer off the rear wheels.

 

The computer controls all regen and limits it in cold weather or when the battery can't take regen for being full, too cold or too hot. When conditions are right for the battery to except charging, 100% of regen is taken from the front wheels before the mechanical brakes are applied. After 100% of regen is applied, the mechanical brakes are applied in the same manner as a car without regen braking. It doesn't matter if the car is FWD or AWD, all 4 wheels assist in stopping the car.

Your question in another thread regarding the change to '09 FEH rear drum brakes was because of cost. The '09 FEH was the first year Ford made a profit on the FEH. Ford made some hell of improvements in the '09, but they had to make some cuts to offset those improvements. The rear drum brakes were a minor change to cut cost when you compare eliminating the battery aux A/C in the '10 models. Ford had to give up on a '13 FEH altogether. You own the best and most efficient AWD SUV on the planet in my opinion, so I wouldn't let rear drum brakes get you down.

Gary

 

That's what I thought, that during 100% regen braking, all such "braking" is being done with the front wheels. In non-hybrids, or outside the regen mode, some of the braking is done with the rear wheels. "Braking" with just the front wheels strikes me as an inherently unstable configuration. So I was speculating that in the awd hybrid, the rear wheels could be engaged to help with the braking in regen mode.

And I assume there are times when the friction brakes are in use at the same time there is regeneration going on.

If I take your comments correctly, you're saying that the elimination of the rear battery aux hvac system in the '10 model was to save build costs. I can see that, since it's a lot of stuff. It should also improve reliability and lower weight a bit. Is it your opinion that the traction battery temperature is not as well regulated in the '10 as the '09? And that this would lead to degraded battery performance (and life)? On the other hand, wouldn't it take some extra energy to run the rear hvac system, which would translate into a bit of a mileage penalty?

Don't get me wrong about the rear drum brakes. I'm on the side that there's nothing wrong with them (though there seems to be proof that they do cause longer stopping distances than rear discs, there seems to be no definite conclusion on this in general.) I know for myself that my rear drums stay cooler than the front discs during demanding descents. Certainly the drums are adequate and require far less costly servicing. I've had an suv with rear discs, and their maintenance cost a fortune.

 

I've got as high as a 65mpg tank in my '09 FWD FEH on E10, so I know how efficiency is effected by HV battery temperature. The removal of the aux A/C in the newer FEH's and FFH not only decreased efficiency, but it shorten battery life. What Ford did is restricted EV use when the battery gets hot instead of keeping it as close to 78F the ideal efficient temperature.

In my '13 Energi, once the battery reaches 113F, you cannot drive in EV no matter how high the SOC is. Here in So. FL, my battery gets to 109F in 92F weather real fast. I have to precondition the cabin while plugged-in charging to keep from getting over a 112F battery temperature in the summer. The only reason I purchased my '13 Energi is because I know how to keep the battery temperature under control in my weather. There is no way I'd buy this car or any other hybrid where OT gets above 98F and not have a aux battery A/C. A heat soaked cabin and battery would just not be efficient and the battery would be short lived.

If you let the A/C go out in your FEH, you will get the "Stop Safely Now" message real fast. There is a reason Ford didn't want the battery to get hot!

Gary

 

So it looks like the penalty in weight and energy for the aux a/c unit more than pays off in battery performance and life. At least in very hot (and probably very cold) places. Sounds like you benefit from going to the trouble of figuring all this out.

Where I've lived since the 70's, it's never gone above 98F, or below -4F. The official overall average is 52F, and I assume that would be higher if only the daytime was included.