Did not find the answer via search ----

I'm not sure I understand regen, this is what I *think* I know. I do not have NAV, only Scan III.

Whenever the vehicle is coasting and not in N, there is regen present. Shifting to L greatly increases the regen.

"Coasting" regen degrades below 60F and disappears at 40F. L regen is present regardless of temp.

Under 7 mph only friction braking is present.

Questions:

Does pressing the brake pedal engage friction brakes or allow the generator to create more electricity by creating more resistance? Is it a combination of both at all speeds?

I seem to get a greater charge pressing the brakes rather than coasting while coming to a stop. Should I do long, slow braking rather than coasting and hard(er) braking? Is this dependent on temperature?

What's the difference between L and using the brake pedal?

Thank You

 

I thought when you were in "D", regenerative braking only occurred when you were lightly touching the brake pedal. The system attempts to use regenerative braking over fiction braking by measuring the difference between requested deceleration and actual deceleration.

 

Pressing the brake pedal down engages the regenerative braking only, unless as mentioned, you're at a low enough speed or regen braking isn't sufficient to give you the braking power you're asking for. This can be due to either the regen being retarded due to cold temperatures or due to you slamming your foot down on the brake pedal. In those cases, you get a mixture of both regen and physical brakes.

I always advocate longer gentler braking to coasting with harder braking, but there are others who disagree with me.

L is exactly the same as D with light braking at all times. The only difference is the programming of what happens when you take your foot off the pedal, there is no physical difference. So, D with light braking and L is the same.

 

Here is a quote from a Ford Patent:

"the present service brake regeneration is applied at 100% effectiveness at ambient temperatures above 60.degree. F. and at 10% or less effectiveness at ambient temperatures below 40.degree. F. For ambient temperatures between 60.degree. F. and 40.degree. F., the effectiveness of the service brake regeneration is reduced in a linear relationship with the ambient temperature. Thus, the service brake regeneration is not as biased toward cold weather operation as with previous systems."

So no, when the ambient temperature gets below 40 degrees F, all regen is not removed. It appears the concern is with ice and snow and effectiveness of the ABS system. Many people have reported regen below 40 degrees and some have reported a loss. It seems I have loss regen even above 40 degrees many times until the vehicle warms up. When I lose regen, I also lose it in "L" also. I don't have many days below freezing here in Jupiter FL, so others may have more to add.

Below 7mph you still get regen in "L" and "D", but there is no regen at any speed in "N". If you shift to "N" below 6mph, you will enter into passive neutral. In passive neutral, the engine will remain in the state (on or off) it was at the time you shifted. In addition, you cannot key start the vehicle in passive neutral.


I use "L" as a brake to slow or stop every time except when I lose regen in cold or hot situations. You must use the pedal to come to a complete stop because of the creep mode at ~4mph. Using "L" eliminates the use of the friction brake pads. I only use the brake pedal for additional regen and more stopping power with the brake pads when I need it.

GaryG

 

Thanks for the info.

I've noticed you cannot start the vehicle in N at a stop, *obviously* different from my previous cars. A fun quirk.

In the short time I've had my FEH, I've always had regen, even below 40F. Or at least it seems that way.

The exit ramp near my home is a significant down grade, and I use L the moment I get in the exit lane. It is sufficiently steep to keep my speed for about a 1/4 mile until I get to the stop light. What's interesting is my SOC has often exceeded 60% (I've gotten 64-65% SOC - is that bad for HV life?) allowing me to EV the the approximately 1.5 miles home (also slight downhill).

 

No, it isn't exactly the same.

If you have a FWD version, even light braking can cause the rear brakes to engage whereas in L, all the deceleration is caused only by the electric motors becoming generators - the rear brakes are not used at all.

L causes a heavier regen when you take your foot off the accelerator or even when lighten the pressure on the accelerator compared to how it would behave in D. Using the brakes (in D or L) allows the computer to decide how much decel to let the generator have and how much to give to the friction brakes.

 

I do not recommend driving in "L" and my test showed a decrease in MPG during steady state speeds below 50mph. You can check out an article I wrote at Cleanmpg.com which has a graph of steady state speeds with and without cruise control. Below the graph is my comments about the same test driving in "L".
http://www.cleanmpg.com/forums/artic...brid--350.html

There is also regen in "D" when you let off the accelerator, so if you really want to coast further and maintain speed the longest, use "N". I time my speed before coming to a stop or slowing down in "N" and shift to "L" to control speed and regen. My main goal is stay in EV below 40mph as much as possible and using regen with "L" helps me do that.

GaryG

 

I do use "L" only in stop and go traffic under 35. I think it helps me to stay in EV mode longer because the low gear mulplies the torque of the motor better.

 

There is no change in final gearing between "D" and "L" in EV or ICE On. The only change is with the amount of regen when you let off the accelerator. In other words, the traction motor is the final gear ratio and it never changes. Higher engine RPM's allows the planetary gear set to split power to the drive wheels and MG1 (generator) till it exceeds the torque of MG2 (traction motor/generator). Shifting to "L" is not shifting to lower gears, it only simulates a lower gear with regen. Using "L" will help you go EV, but will reduce MPG under 50mph. When I want to go EV, it is planned at the speed and battery SoC I want to.

GaryG

 

I find, and I think everyone will agree, you need two driving styles.
One for +40'F drives, and one for cold weather drives.

Performance of EV and regen is MOSTLY about the car temperature.
( Not outside air temperature )
My car behaves normally when I have a hot engine, and 70'F battery, even if the outside air is in single digits. But how often do you have a 70'F battery when the weather is in single digits? Not often.

Most people, most of the time, have a cold battery, when the weather is cold. Few people park in a heated garage, and even fewer use the 120v plug in battery warmer like I do, so for most people, it is one and the same.
Cold weather = low EV and regen.
But is does not have to be that way. Technically speaking.
-John