According to the US patent granted to Ford the FEH/MMH regenerative braking is disabled (assuming actual patent application) if the OAT hovers around freezing or below. Too much danger of encountering slippery roadbed conditions wherein engine compression braking or regenerative braking on FWD or front torque biased AWD vehicles is potentially unsafe.

I can assert that regen for certain takes place from -20 all the way on up to 75 or so (anything hotter than that, and we consider it unsafe to go outside) provided the battery is warm enough to take it. And it works (and works surprisingly well, I think) in very slick conditions.

We get the condition pretty from time to time that the road surface is very cold and air temps go into the upper 30's or 40. Since there is hard ice on the road, the surface gets wet on top of that, and it is, what we call, "really slick". Slick as in, parked cars without studs slide around the parking lot from wind" slick.

Even under those conditions (without the recently added studded tires), regen worked and was not particularly squirlley (I don't really know how to spell that). But also below freezing and below zero (when interestingly, it starts to get slicker than when it is, say, 10 degrees), regen works. Except for the temp of the battery, I've never noticed it not working for any period of time.

I drive in "L" quite a bit and I can also say that at 20F or so the regen is still active and it feels fine. They may have a patent and have decided it wasn't useful and not included the work on the FEH.

Hi Tim

It may be a good idea that you read what Willard may be reading. It's not an on and off situation, so I think disabled is not a good term for Willard to use. Maps are used for different situations and temps. An ABS event can disable regen for obvious reasons.


Temperature compensated lift-throttle regenerative braking
The amount of regenerative braking that is applied to the wheels (105) of a vehicle (100) is based on ambient temperature and a lift-throttle event. An ambient temperature sensor (108) monitors the temperature around the vehicle. Based on the temperature, a map is selected (204, 212, 214). If a lift-throttle event occurs, then the map is applied (206, 208). Compression regenerative braking is reduced to zero if an anti-lock braking system event occurs or if the throttle is re-applied, or both (216, 218, 220, 222).

http://www.freepatentsonline.com/658...hlight=5343970

You and Andy are right IMO.

GaryG

Actual regenerative braking (BRAKING!!) can only occur upon a lift-throttle event/circumstance wherein an ordinary vehicle would incur engine compression braking. Remember that when the ICE is producing torque to move the vehicle forward it can simultaneously be used to charge the hybrid battery.

Look at what is going on at the moment throughout the industry with regards to alleviating safety issues with automatic transaxles and engine compression braking on FWD or front torque biased AWD vehicles. Toyota/Lexus, Ford, and VW are all taking a lot of HEAT over what is being referred to as 1-2 second throttle lag and/or downshift hesitation delay in their automatic transaxles.

Seemingly late in the last century the industry became aware of the additional hazards of FWD on adverse roadbed conditions and began to adopt a new transaxle shift pattern/schedule to compensate. Unlike the FEH/MMH a non-hybrid automatic transaxle vehicle does not have the ability to instantly remove engine compression braking when ABS activates, so they must do it, upshift, the instant a lift-throttle event occurs.

The Ford patent is simply a method of accomplishing the same thing for FWD hybrids.

Look at it this way, if you were driving a stick shift FWD vehicle and you KNEW the roadbed to be slippery what would be your automatic secondary reaction if/when you lift the throttle, especially a FULL lift throttle?

Depress the clutch pedal.

That's all the industry is trying to accomplish, but automatically.

It was a bit warmer this morning... 7 above... when I started the FEH. No warnings.

Thanks for the reminder on stored codes. I'll be sure to mention that what I bring it in.

I think we should all heed what wwest is saying......keep it on all the time.

Just kidding, but it is true that when you're in doubt in a front wd, aim and shoot!!

I've driven FWD vehicles in snow and ice all my life. I had a Dodge Horizon in HOUGHTON, MI (thats ~230" each year). Having not driven a RWD, to me there isn't really an issue... Its just different. I've always taken corners such that all braking is done while the wheels are straight... by the time I reach the corner the idea is to be going so slow such that I need the gas to pull me around the corner, and the brakes are not applied while rounding the corner.... so far its kept me out of trouble pretty well. I've never missed a corner yet in 20+ years of driving, so I must be doing something right. If I do feel it let loose... I give it a bit of gas which I think is similiar to what wwest is describing.

In Houghton I used to live on Garnet street (any MTU grads out there?)... Its got a slope on it that is just over the top. If there was any ice or snow geting down was essentially a controlled slide. You never went up unless you had chains. I remember the trick was when you were just about at your driveway you started your turn and gassed it! It was kind of fun acutally.

This is my first AWD vehicle.... I'm not entirely sure what to expect but you can be sure I'll take it easy.

Here's an update. An FEH owner in Reno reported the same issue. Her service shop reported "ABS test C1526, replaced master cyl. per TSB 05 08 05." Another owner said it is a sensor failure in the brake master cyl. in early production '05s. An online reference says DTC C1526 may occur along with DTC C1524. Another reference refers to TSB 06 10 14, "ABS light on and DTC 1475, Hybrid built between 8/2/04 and 3/30/06, Revised."

This is from a post in this forum a couple of years ago:


TSB
05-8-5 ABS AND BRAKE WARNING LAMP ON WITH DTC C1526 - DTC C1524 MAY ALSO BE PRESENT - VEHICLES BUILT PRIOR TO 2/11/2005

Publication Date: April 8, 2005

FORD: 2005 Escape Hybrid

ISSUE:
Some 2005 Escape Hybrid vehicles built prior to 2/11/2005, may exhibit the yellow ABS and the red brake warning lamps illuminating after the engine is started, and an increase in brake pedal effort. Diagnostic trouble code (DTC) C1526 (Brake Pedal Travel Sensor) will be present in the ABS module, C1524 (Brake Pedal Travel Sensor Calibration Incomplete) may also be present.

ACTION:
Install a revised master cylinder. Refer to Workshop Manual Section 206-06.


PART NUMBER PART NAME
5M6Z-2140-B Master Cylinder


WARRANTY STATUS:
Eligible Under Provisions Of New Vehicle Limited Warranty Coverage

OPERATION DESCRIPTION TIME
050805A 2005 Escape Hybrid Replace Master Cylinder (Do Not Use With 12650D, 2140A, 12651D70, 2000A) 1.6 Hrs.

Update update. Shop could not find anything wrong and they did not find a current error code. They tried to charge me $115 for looking, despite my extended warranty. We settled, without much hassle, for the $50 deductible.