Brakes?

Discussion in 'Clarity' started by hamr4267, Sep 13, 2019 at 1:16 PM.

  1. hamr4267

    hamr4267 New Member

    So I learned about the paddles, and when I apply the brake, I get regen. But what's actually stopping me? At first I thought there was a regen system near each wheel that worked as a brake and added regen, and the discs would only get touched if you really need to stop quickly...
    Also, I like to hit the left paddle 4 times and get 4 chevrons. But do I really gain anything by using the paddles? Would just gently applying pressure to the brake pedal be the same? Occasionally I stop using the paddles, then when I am ready to accelerate, I still see the 4 chevrons. This triggers my OCD and I feel as if I'm accelerating and braking at the same time (although the chevrons go away after a couple seconds). Does the system automatically sense my foot on the accelerator and turn the regen off? Is there a delay?
     
  2. css28

    css28 Active Member

    As with several other hybrid vehicles, the car is smart enough to apply regen braking based on the brake pedal application. This happens through the transaxle/motor unit so it only affects the front (driving) wheels. The friction brakes get involved with heavier braking and also at very low speeds.
    If you're using the paddles alone (with your foot off the accelerator) you're getting the same effect but with the guarantee that there's no friction braking taking place.
    The advantage of doing it through the brake pedal without the paddles is that the regen is modulated according to your pedal pressure rather than in one of four chevron setting levels. There's little actual wear of the friction brakes in gentle braking, even when using the brake pedal.
    The chevron display is to indicate what level of regen you'll be getting when you let off the accelerator again. Unless you're in Sport mode the system automatically resets the chevrons shortly after you resume accelerating.
     
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  3. petteyg359

    petteyg359 Active Member Subscriber

    I regularly get a few more tenths of a mile estimated range at every stop light or sign by using the paddles before I ever touch the brake pedal. They're also great when going down a steep hill; you'll still have to apply the physical brakes, but you get more in return.
     
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  4. Agzand

    Agzand Active Member

    The paddles are great in sport mode when there is slow moving traffic and you don't want to us adaptive cruise control. Also great in mountain roads, you don't have to brake on every corner.
     
  5. craze1cars

    craze1cars Well-Known Member

    My answers to 4 original questions in order:

    No, yes, yes, no.
     
  6. petteyg359

    petteyg359 Active Member Subscriber

    Pretty sure your first answer is incorrect. The brake pedal WILL apply the brake pads at some point. I can "coast" to 8 mph with the paddles and guarantee the brake pads were never engaged. This is the whole reason people use sport mode to keep the regen level at maximum.

    removed wrong graph
     
  7. insightman

    insightman Well-Known Member

    Actually, by default, you're driving with one hidden chrevron. You need pull the left paddle only 3 times to get 4 chevrons. If you pull the right paddle without first pulling the left paddle, you see the hidden single-chevron light up.

    Also, it's the traction motor that slows the car when you use the paddles (it helps the friction brakes when you use the pedal). The motor switches to generator mode and it's such a powerful generator that it takes a lot of torque to generate the electricity it's sending to the battery. That traction motor/generator is always connected via gears to the front wheels (even when the clutch connects the engine to the front wheels). The energy required to turn that big generator is so great that the Clarity slows down as it generates electricity. If your battery is already fully charged, however, there is nowhere to put the regenerated electricity, so the Clarity PHEV does something totally counter-intuitive: it starts the engine. Here's a mode diagram I made for last year's National Drive Electric Week gathering. The controversial engine-starting conundrum appears in the bottom-right diagram.
     
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  8. craze1cars

    craze1cars Well-Known Member

    Whoops I completely missed question number one...I previously answered two thru 5. My mistake.

    That answer for #1 is: disc Brakes at each wheel.

    And everything Insightman said is also correct.
     
    hamr4267 likes this.
  9. leop

    leop Member

    Please note that the regen braking only occurs at the front wheels. If only regen is being used for braking, the car is only using front wheel brakes. I cannot say how much the rear disk brakes are used when braking with the pedal but I think that there is some rear braking from the rear disks, for stability purposes, all of the time. And, I would assume that for light to medium braking where the regen does much of the work, that the rear disk brakes are used much more than the front disk brakes.

    When I did my first yearly service last February, I measured the disk and pad thickness for all for corners. The rear disk surfaces were very much shinier than those on the front. In addition, the front pads were all at 10mm thickness while all of the rear pads were at a bit over 9mm. I do not know the starting pad thicknesses (as I did not measure the pads on the brand new Clarity in 2018) so I cannot say that all the pads started out at 10mm thickness when new. Next year when I do the second yearly service, I will again measure the pads and will have a better idea if the rear pads are more used.

    I, too, will say that I am very impressed with the combination and control of the regen and friction braking on the Clarity.
     
  10. Landshark

    Landshark New Member

    This question may warrant its own thread.

    If there is no rear wheel regen, why must the car be towed on a flat bed truck rather than a tow dolly with the front wheels off the ground?
     
  11. MrFixit

    MrFixit Active Member

    The only thing I can think of is there are some conditions that could result in automatic application of the parking brake.
     
  12. 2002

    2002 Well-Known Member

    The owners manual mentions damage to the "drive system" for some reason:

    Emergency Towing
    Flat bed equipment
    The operator loads your vehicle on the back of a flat bed truck. This is the only way you can safely transport your vehicle. Any other towing method will damage the vehicle’s drive system.


    However the emergency responders guide says something different:

    Emergency Towing
    The preferred method is to use a flat-bed tow truck. If wheel lift equipment must be used, be sure to suspend the front wheels and release the parking brake. Be aware that when rolling a Honda Clarity Plug-In Hybrid with the front (drive) wheels on the ground, the electric motor can produce electricity and remains a potential source of electric shock even when the high voltage system is turned off.

    It says the document is "Prepared for Fire Service, Law Enforcement, Emergency Medical, and Professional Towing Personnel "


     
  13. PHEV Newbie

    PHEV Newbie Well-Known Member

    Honda advertised that the Clarity has the most efficient regen in the industry. Sorry I can't find the ad but it indicated that it will stay in regen during normal braking and apply the friction brakes only at the last moments of braking. I believe this is true. For a while, I had a bit of brake noise from friction brakes (which I could clearly hear when backing up, when there seems to be zero regen) and I only heard the friction brakes engage at the very last moment. That means that nearly all the braking is via the front wheels during normal braking. Of course, in hard braking, the friction brakes will engage automatically. Also, the ABS system will engage the correct brakes if it detects any imminent lockup.

    To the OP. If you look at the energy gauge, max regen is only achieved using the brake pedal. Using the paddles, you can only achieve partial regen at max chevrons because that's how it is calibrated. I've stopped using the paddles (except going down long mountain passes) because the brake pedal provides the most range in regen and it does not engage friction brakes until the last moment unless you brake hard.
     
  14. 2002

    2002 Well-Known Member

    I have sort of assumed the reason paddle regen is limited is because it does not activate the brake lights. I suppose they could have had a fifth or sixth chevron or whatever that activates the brake lights, but they chose not to.

    I also wonder about what most of us have noticed which is that oftentimes at higher speeds only three chevrons of paddle regen are available, after you slow down a bit then four become available. And that's even when the battery is nowhere near full. One theory given was that four chevrons of regen would charge the battery at too high of a rate. But if that's the case then using the brake pedal at higher speeds would have the same problem and thus would have very limited regen and the rest friction braking, but I don't think I have seen that to be the case. Plus we know that pressing the brake pedal gives you much higher regen than even four chevrons of paddle regen. So perhaps the three chevron limit is also due to brake lights, maybe at higher speeds they feel you shouldn't be slowing down too fast without activating the brake lights.
     
  15. Landshark

    Landshark New Member

    Any theories on how the electric motor could produce electricity with only the rear wheels rotating?

    I imagine the risk of electric shock would be limited to someone touching a non-insulated terminal while the vehicle was in tow. There must be a YouTube video somewhere demonstrating this maneuver.
     
  16. 2002

    2002 Well-Known Member

    The document said it generates electricity during towing when the front wheels are on the ground, not the rear wheels. Interestingly it says it will do this even when the high voltage system is turned off, which I assume they are referring to pressing and holding the power button for three seconds which emergency responders do to shut down the HV system and also deactivate the airbags. As to what the risk is I don't know since it seems unlikely anyone will be touching the car while it is being towed. Typical electronic devices store energy in capacitors and such for a while so there is a slight shock hazard even after you unplug the device, but I'm not sure how much energy could be stored in the system while towing that would make it dangerous once stopped.
     
  17. Landshark

    Landshark New Member

    Ah, yes. Now I’ve read it correctly. Front (drive) wheels generating electricity makes complete sense. The sentence came immediately after “...be sure to suspend the front wheels...” so my mind already had the front wheels off the ground.

    Sort of like the sign in the convenience store that read “Engergy Drinks” and everyone there though it read “Energy Drinks” until they read it 3 times.

    Still curious how towing with the front wheels off the ground would damage the drive system. I know, because the manual say so.
     

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    Last edited: Sep 14, 2019 at 2:54 PM
  18. insightman

    insightman Well-Known Member

    There's concern that the rear overhang might contact the pavement or a driveway incline if the front wheels were raised too high.
     
  19. Landshark

    Landshark New Member

    How would that damage the drive system?

    The rear skid plate is 8” off the ground, the rear tow hook is 10”, the rear bumper trim is at least 12”.

    The wheel base is +/- 108” the rear overhang is +/- 41”. Ratio is roughly 2.6:1. Raising the front tires 5” onto a tow dolly would lower the rear less than 2” leaving at least 6” of ground clearance. The Jetta I just sold had 5.6” of clearance. A tow truck lifting the front a foot or more is a completely different situation.

    Tail dragging wouldn’t make my concern list using a tow dolly. Drive system damage would.

    If the rear wheels are not connected to the drive train or regenerative braking what could be damaged? Parking brake application? Does something other than pulling up on the P Brake lever apply the brake?
     
  20. insightman

    insightman Well-Known Member

    I agree no drive train damage could result from towing with the rear wheels on the pavement. The danger of tail-dragging would be the main reason to choose a flatbed truck versus towing with the front wheels raised.
     

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