Efficiency of Regenerative Braking

I am doing it mainly because I like the way the car drives with Sport and full regen. Especially on the highway with an unexpected quick stop I like slowing down as soon as I get off the throttle but before I push the brake pedal. I do wish it was stronger and didn't have to actuate every start up but this is ok.

 

Well, I can't think of an easy way to prove or disprove your theory, but...

It just seems completely counter-intuitive to me that the designers of a modern PHEV would fail to use regeneration to capture energy that is normally lost when stepping on the brake. You are trying to say that regeneration only happens when you release the 'gas' pedal, but don't touch the foot brake. You can obviously increase this effect with the chevrons, but as soon as you touch the brake, regeneration stops and it is all lost to friction (even though the display goes deep into the charge range)? This just doesn't seem plausible to me.

My contention is that the power/charge gauge is a valid indicator of electrical energy being consumed for propulsion, or being captured through regeneration when decelerating (whether by paddling, coasting, or braking). Maybe there is some nuance in engine drive mode, but that is a nit because engine drive mode disengages during deceleration anyway.

If your only proof otherwise is the fact that you hear brake drag immediately when you touch the brake pedal (and you expect to see some discontinuity on the power/charge gauge, but don't), that is not convincing to me.

From the diagram provided earlier, it is interesting that there are a couple of pressure sensors in the hydraulic brake system. Those pressures might be informative as to how much friction braking is actually being applied. It would be interesting to instrument these pressure sensors somehow and see how they behave.

Until proven otherwise, I continue to assume that the regen paddles are just a gimmick because I believe I get just as much regen through the foot brake. There are enough things to concentrate on while driving without an extra gizmo like the paddle if it is really adding nothing to the equation like I suspect.

 

It makes no difference if we use the paddles/chevrons, the brake pedal or a combination. The regenerative braking system will recapture ~50% of the available kinetic energy that would otherwise be converted to heat on a vehicle with a conventional braking system.

The paddles provide 4 levels of regenerative braking that range from light to moderate. The lightest setting is a permanent fixture. The brake pedal has the ability to send more regenerative energy to the batteries than the most aggressive paddle setting.

There is no meaningful data to be gleaned from the power gauge, other than “something is happening”.

In a nutshell it is ~50% efficient. What makes it happen is complicated. Understanding the basics isn’t too challenging.

 

I thought it might be better than 50%, but I totally agree with your description...

 

I believe this is exactly what is happening. I guess neither of us can confirm or deny this unequivocally.

 

No. There is no regen when you brake with the car in Neutral. I live in foothills and that is how I avoid the ICE coming on when I'm headed down my street with a full charge.

 

This post by @AnthonyW was quite some time ago, here:
Anthony_Gauge_Post

He was able to identify the nature of the charge/power when in the 'positive' region by monitoring the HV battery current with his ScanGauge. He found that seemed to be linear above 30 amps (there was a scale change below 30).

He also stated that he was unable to ascertain a clear relationship regarding the current vs. tick marks when in the green region (regen)...

 

What evidence can you provide to support that statement?

Regenerative energy is sent to the batteries when the rotational direction of the traction motor is reversed from the direction it rotates in propulsion mode. It becomes a dynamo to the tune of one chevron when the foot comes off the accelerator. Click the paddle three times and we have 4 chevrons of regenerative mojo. Step on the brake pedal and even more, yes more regenerative energy is sent to the batteries.

We don’t even need to fuss with the paddles to get regenerative energy. If the one invisible chevron doesn’t slow the car sufficiently, use the brake pedal. It will utilize the traction motor to slow the car.

 

Interesting. I haven’t tried going downhill in neutral, but I haven’t had the ICE come on after a full charge when going down an average 8.8% grade for half a mile either.

It makes sense in that the traction motor would be disengaged and therefore unable to provide any braking power. Slowing would be task of the disc brakes.

Thanks.

 

Ford and Eaton are developing a regenerative braking system called Hydraulic Power Assist, that they claim will be capable of recovering up to 80% of available kinetic energy. It is bulky and will probably be initially utilized in larger heavier vehicles.

The ~50% figure is commonly cited for systems such as ours. Much like MPG, it will be variable, depending on individual driving habits.

 

I agree.

I consider the POWER/CHARGE Gauge's positional information useful even if there are no meaningful units being displayed. This gauge can be a valuable tool for learning how to maximize range. Also, the gauge indicates the relative proximity to the the ICE-activation threshold.

 

Would you agree that the brake pedal alone (with no chevrons added by the paddles) can send more regenerative energy to the batteries than the most aggressive paddle setting? I think that it does...

@ClarityBill may feel that friction braking is always significant whenever the petal is pressed and therefore you cannot achieve maximum regeneration with the brake pedal alone.

 

How did you come to this conclusion?

Have you done repeated decelerations on the same road, from the same top speed to the same slow speed, with all 4 chevron settings and observed the regeneration results as displayed on the regenerated energy gauge? Dang! There isn’t one of those. Guess the increase in EV range would be the best estimate.

How do you know the Clarity doesn’t do this? There are only 4 chevrons to be displayed. Four chevrons does not indicate maximum regenerative braking energy.

 

For further interesting reading on the topic, here are few of the former threads on regen braking.

https://www.insideevsforum.com/community/index.php?threads/brakes.6831/

https://www.insideevsforum.com/community/index.php?threads/regen-capability.6340/

https://www.insideevsforum.com/community/index.php?threads/can-you-tell-when-the-friction-brakes-engage.6312/#post-70562

https://www.insideevsforum.com/community/index.php?threads/regen-paddle-braking.5320/#post-63658

https://www.insideevsforum.com/community/index.php?threads/is-regen-in-effect-when-accelerator-is-stepped-on-under-sport-mode-and-regen-is-turned-on.5701/#post-62182

 

I believe the POWER/CHARGE Gauge's charge segment displays only the power the traction motor is generating and the gauge shows more regen with pedal than paddle.

 

I’d like to correct the above statement.

Torque is applied in the opposite direction of the motors rotation. The direction of rotation is not reversed.