Regen paddles doing something I don't understand

The most efficient way is still coasting, so I always try to avoid using the brake or the paddles. I think the paddles are only there to make you decelerate more smoothly, they are not for fuel economy.

 

The consensus here (with no verification) is that the brake pedal activates regen first, then applies friction at some point in the pedal travel. Only one poster appears to be able to detect when the transition occurs. Activating regen first would be consistent with Honda's attempt to maximize efficiency. Watch the Power/Charge Gauge for clues (but no solid answers) to the braking system's behavior.

 

Why do you think this? It would be silly to apply friction brakes and turn perfectly good kinetic energy into heat when it can be captured as charge in the battery, and I would be amazed if the engineers at Honda made such a basic goof. Yes, at some point the brake pedal is going to invoke the friction brake - it better, or we would be in danger of randomly ramming into things.

Let me try to reword this . . . If you have a given velocity, this determines an acceleration that is required to reduce that velocity to zero in a certain distance. The acceleration determines a force, based on the mass of the object (a Clarity, in this case). That force can come from regenerative braking or from friction. If the force is higher than the regenerative braking is capable of producing, then of course you're going to have to engage the friction brakes. Or if the driver insists on pushing so hard on the pedal that they engage, then yes you will waste part of the kinetic energy in heat. But I see no reason to think that there is any difference between my using the paddles to apply the force versus using the brake pedal as long as I don't dip past the limit of the regen braking.

 

I'd like to hear the answer to this also. Like OP, I'm just a week in. I like to stay in Sports mode to have the torque available if I want it and keep regen at max. It seems that the car still stays in EV mode and I get the same battery mileage if I'm easy on the gas pedal. But I also noticed the Chevrons sometimes go to 2 in Sports mode and not sure why.

 

Claire & ozy: As I mentioned in another thread (https://www.insideevsforum.com/community/index.php?threads/regen-limited-in-cold-temps-or-high-soc.4229/), it could be cold temperatures or if the battery was already at a high state of charge, or perhaps the other reasons listed in the manual from that post.

 

If regen is applied first, the following statement from page 434 of the users manual does not make sense.
"Applying constant pressure to the brakes while going down a long hill can cause the brakes to heat up, resulting in a loss of stopping power. Therefore, when descending a long hill, release the accelerator pedal and allow regenerative braking to slow the vehicle down. To adjust the rate of deceleration, use the deceleration paddle selector."

 

It follows the Law of Conservation of energy. When you go down hill, the loss of potential energy is converted into kinetic energy. By applying the friction brake, you convert part of the potential energy into thermal energy, thus you prevents the kinetic energy from increasing. While applying the regen first, you convert potential energy more into electric energy than thermal energy, they do the same thing as you want, which is reducing the kinetic energy. The regen deceleration is not as powerful as the friction brake, so, if and only if the system deems that regen is not enough, will the friction brake be triggered.

 

I can see how you could assume that, but my assumption would be that they're aiming that prose at the people who think that it's better to brake in "surges" - brake heavily, then not at all so the brakes can cool. The ability to keep a constant braking would be a real use for the paddles. I wouldn't know, having never driven the Clarity down a mountain.

 

You misunderstand the point. If only regen braking is applied first when using the brake pedal, there would be no reason why you should not use the brake pedal when going down a hill. They would not advise to use the paddles to avoid loss of stopping power. Either the manual is incorrect or friction braking is used when using the brake pedal even when only light braking is required.

 

In earlier Honda hybrid cars, it was easy to feel the transition from regen to friction as the brake pedal was depressed. It's unlikely that this latest generation of Honda hybrids would abandon this scheme and activate the brake calipers at the beginning of the brake pedal's travel when regen braking is sufficient get the job done.

 

It is Japanese English. There should be a threshold which triggers the friction brake, below that, regen is used, otherwise the brake kicks in. I do understand that they wanted to say constant pressure over the threshold, but it is not very easy to explain in fact.

 

Well put. Honda has the worst owner's documentation of any car company I've seen. I wouldn't have thought that you could make a manual verbose and incomplete at the same time, but they have managed to do that while in many cases making the information that is there impossible to understand.

 

I've tested this recently and could not get the brakes light to go on, even with all four chevrons coasting from about 40mph. I was doing it in pitch black, and could see the reflection in the rear view mirror and the difference when I actually tapped on the brakes.

 

It was perfectly understandable to me...

Regarding earlier comments on "gimmick" paddles, they're obviously not so. Your brake pedal will only apply regeneration at the level you have set. If you're going down a mountain, or trying to get into an annoying short turn lane on a 55+ mph road, if you don't use the paddle, the regeneration won't be enough to slow you, so you will be riding the brake pads. You MUST use the paddles to increase the regen level. There's no gimmick there.

 

Except that the paddles don’t increase the pedal regen. You can actually get more regen with the pedal than you can with four chevrons of the paddles in some instances.
I think why the manual says to use paddles on long downhills is that you can’t tell when the friction brakes are activated (kudos to Honda). So the unwashed masses could end up over heating the brakes on a severe downhill, while using paddles will never engage the brakes.

 

I think now I am quite clear about how it works.
Coasting actually means level 1 regen, whenever you remove your foot from the acc paddle, regen starts, that makes sense, and it explains why you can't reduce regen to 0. Regen does not have enough power to force it to a full stop, I guess but I haven't tried. The degree of friction brake applied is different from a normal car, regen plus the actual brake equals the level you supposed to have with a normal car. You have to keep the car at least at a constant speed to avoid regen from happening.

 

It doesn't say anything about how much pressure is applied to the brake pedal. It's quite possible the first pressure on the brake pedal only applies regen which would not negate their comment. But Honda's advice is use the paddles which to me means the paddles never apply the physical brakes. It's just easier. Honda didn't give us any indicators regarding when the physical brakes are in use.

 

If it were necessary to go over a threshold to slow down enough, then friction braking would still be needed even with the paddles used. Still doesn't make sense. I found a document online which I assume applies to the Clarity since it was written by Honda engineers. Still not enough details to completely understand the system, but the goal is obviously to use a combination of regen and friction braking to achieve the braking corresponding to the driver's pedal pressure (or possibly pedal travel) when the brake pedal is pushed. Web site is https://wenku.baidu.com/view/cc1098582f60ddccda38a0b8.html

 

By observing, I found that likely regen and friction brake is mutual exclusive. When I have level 4 regen enabled, and I brake to a full stop, although it still displays level 4 regen, immediately after I release the brake paddle, it disappears.

 

The most ideal is to drive at a constant speed, not even coasting the car. Or the second best is to avoid using the regen and brake pad, let it coast. Even though regen is there, the energy loss during the conversion can't be avoided.