This has become increasingly noticeable on my 07 TCH.

This happens regardless of the following;
Engine warm. Engine Cold. Full battery charge (green bars) to Low battery charge (purple bars).

When decelerating and using light braking from just about any speed above 30 MPH, I get down to about 20mph and suddenly I lose regen braking. This feels almost like an acceleration (although I know it is not) but suddenly I'm coasting and not slowing as quickly..

It does not happen all the time but during an hour long drive through town, with maybe 20 stops, it will happen 4 or 5 times..

If it happened consistently, it would not bother me quite so much. It would also be easy to demonstrate to the service writer at the dealership..

I've not had it back into the dealer - yet - but wanted to pass it by you folks here to see if anyone else has experienced it.

I did a search and found that a couple of HCH owners had this issue a couple of years ago.. Different car and system though - so not really relevant..

What say you TCH'ers ???

 

Could it be the 'breakover' point where there are not revs from the motor (that is being driven by the wheels to regenerate) and the conventional brakes are cutting in?

If there is not energy recovered from the wheels running the motor 'backwards' to make it a generator, the old style 'disc and pad' system would take over.

This is seriously oversimplified because of the technology involved, so I am omitting a _lot_ of steps.

 

There are several reasons why the brake controller (the computer that controls the brakes) may decide to use the mechanical brakes, either instead of or in addition to the generator braking. Any one of them can affect the decision for any single braking event.

Some of the reasons are: If the battery is too full, or too hot, or too cold, or otherwise cannot take the additional charge; If you hit the brakes hard, and there is too much energy for the generators to absorb; If you increase pedal pressure suddenly or rapidly, signaling an emergency stop that requires maximum braking effect; If you are going too slow; If the RPM calculation doesn't work out because the gas engine needs to be running for some other reason (such as catalytic-converter temp, or engine temp); If one of the several temperature sensors in the electric motors or high-voltage system is too high; I'm sure there are others.

Basically, there are good reasons why they use a computer to control the braking systems. The fact that you don't always understand why it does something does not make it a defect.

 

I noticed the same thing, and I think the answer is not a technical issue. It's getting colder outside and your tires are getting older. Both these conditions mean the tires don't have the traction of newer tires on a summer day. All it takes now is a minor bump for the anti-lock braking to disengage the regen braking (remember regen only occurs on front wheels, so if the ABS gets the least bit concerned it will dump the regen in favor of 4 wheel mechanical braking).

On my TCH, it used to almost never disengage the regen, but now any minor bump or loose dirt encountered during braking with cause this. I've gotten in the habit of letting the brakes off just for a split second over this terrain to avoid this...

 

Yes, remember that ABS doesn't necessarily engage, just get to the point where it would normally engage except the initial ABS "action" will be to completely disable regen.

ABS may be "programmed" to be more sensitive as the outdoor climate cools, Ford, on the FEH/MMH, reduces the level of regen as the OAT declines toward and below freezing as a safety measure.

 

When decelerating and using light braking from just about any speed above 30 MPH, I get down to about 20mph and suddenly I lose regen braking. This feels almost like an acceleration (although I know it is not) but suddenly I'm coasting and not slowing as quickly..

Big-Foot

You did not mention if your traction battery shows a full charge.

You can duplicate what your saying above. Find a area with no traffic. Try slipping the car into neutral 'during light braking' at about 20/25 mph. This should remove any regen braking. Any braking in neutral will be mechanical.

Move the lever to drive to engage the normal regen braking if needed during this test.

You will find these Corolla sized brakes on the TCH don't slow as well when not paired up with the regen braking.

 

Hi Guys,

Thanks for your responses..

Along with the other parameters I stated in my first message, let me add a couple I forgot. It can also happen whether I am in EV mode or ICE is running.
Also - It's happened when it was 80 degrees and also 35 degrees.
When watching the nav screen where it shows regen function (arrows going from motor-generator back to battery, the arrows do not stop when the regen function drops.


Now - in the order of your messages;

RadioTek - If it did this consistently, I'd be inclined to go along with what you said about the regen not working that low in the speed range..

SteveHansen - I'm not really categorizing this as a defect. Although it's inconsistency may indicate that it is... Traction battery state of charge does not seem to have any bearing as it can either be full or drained. Hitting the brakes too hard - remember that I've been decelerating for a while now at a constant rate when suddenly the regen cuts out. It might be an odd combination of other sensor readings that is causing it... Don't know..

Droid13 - Given the outside temperature variation when I've had this happen, I don't think it's temperature caused. The tires (like the car) are in excellent condition. Only 17k on the clock. Tires are like new yet and full pressure.
You DID hit on something that may be the trigger though.. I will pay attention to the smoothness of the pavement when the regen cuts out. I don't recall there being any bumps of note as we are not in Pot-Hole season here, that starts in a few months..

wwest - Given the light braking pressure being applied here, I'm thinking that I am well clear of the ABS system doing anything - other than (potentially as Droid13 also thought) maybe a bump in the pavement causing the regen to cut-out in anticipation of an ABS event.. The wheels have not been off the car since I bought it - I will pull them and make sure that the tone-rings on all 4 corners are clear of any debris/dirt and I'll double check the clearances for the hall-effect sensors.

rburt07 - State of charge in the battery (traction) does not seem to be a factor. I have (coincidently) put the car into neutral to do the same braking and while there is no regen, braking is consistent and smooth. When in neutral and coasting down from 40 MPH, I can put the car into drive and regen immediately comes into play.. The only brake issues I have with this car are the same that others have talked about - moaning of the brakes when cold and backing up in reverse..


Again - When I say that I am braking lightly - I'm braking just enough to trigger the regen. Think of it as the amount of braking force you need to trip the Cruise-Control...

So my primary reason for laying all this out here was hopefully to find out if others had experienced the same thing and what / if anything / did they do to resolve it...

Thanks again guys and keep them coming...

 

My engine shuts off when I gradually slow down for a red light. The town were I live has a railroad overpass in the south edge of town. Coming down from it gives me a time to ride my brakes for a ways. At night it's quiet and with no other cars around it gives me a chance to hear the generator spinning. I can vary that with my brake pedal when i'm down to 15 to 20 mph when the engine is off. I'm thinking you might try that to see if you can hear the generator spinning up when this problem occurs.

It's best to test at night. During the day I can't hear the generator as well, due to traffic and the blowing wind.

 

Do you have any arrows on the MFD showing the direction of charge? No that that is a perfect instrument of measurement but I am wondering if you are ending up in a "glide" state with no arrows. I wonder this because you have repeatedly said you are "lightly" pressing the brakes.

I don't think I have notice what you describe. I do notice you can get an odd feeling if you catch the system in the middle of switching power sources or stopping forces.