Brake light indicator for regen braking

Discussion in 'Clarity' started by gedwin, Sep 8, 2021.

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  1. ENirogus

    ENirogus Active Member

    This is a great idea, I may have to try something on my Kia
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  3. Kendalf

    Kendalf Active Member

    What year Clarity do you have? It's weird, when I first got my car (2018) I was very excited to test the regenerative braking and I used the right mirror blind spot camera to detect when the brake lights came on while driving on a dark street. I was absolutely positive that I did see the brake lights come on with regen. However, several months later when there was another discussion on this in the forum (it comes up every few months) I decided I wanted to capture this on camera. But all my attempts to get the brake lights to come on with regen only while the camera was rolling failed. I used regen when coming off a freeway at high speeds as well as on local roads. But even with maximum regen in effect, the brake lights did not come on in my car, and I became convinced that I must not have seen it happen previously.

    So now with your results I'm back to being confused about whether this does or does not happen. And if it does, I'm wondering if its a change they did with newer models versus the original batch (mine was purchased Jan of 2018, one of the first several thousand produced).
    insightman likes this.
  4. There are indeed specifications to which the cars will be constructed.

    This is from
    UN Regulation No. 13-H

    Uniform provisions concerning the approval of passenger cars with regard to braking


    I suppose the rate of deceleration will vary depending how loaded the car is, which would be why there is the "may be generated" band, so it wouldn't directly correspond to a particular regen level under all conditions.
    TomL, gedwin and dnb like this.
  5. insightman

    insightman Well-Known Member

    Now someone with an app will hopefully tell us if the Clarity PHEV's regen braking can achieve 0.7 meters per second squared.
    John Lumsden likes this.
  6. gedwin

    gedwin Member

    Mine is a 2019 model year, manufactured 12/2018.

    I hope you saw my followup post that even in my car, it seems to be tied in to my battery SOC. Test yours with a full battery and see what happens?

    I see others have posted regarding the deceleration requirements - that is beyond me. I can just tell you if the light comes on or not!

    Sent from my iPhone using Inside EVs
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  8. gedwin

    gedwin Member

    I had opportunity to drive yesterday starting with a full battery and wet/rusty brake discs, and I learned something that was entirely new to me but not sure if it is already known with this forum: use of the paddles can indeed trigger the friction brakes.

    Evidence while the battery SOC is near 100%:
    - brake lights are triggered by the paddles when the battery is at full capacity, but seem not be when a few miles have been driven off the battery. (This I had already observed, but repeated it again.) When completely full, the brake lights come on even with just 1 chevron of paddle. Later after driving a bit, only the 3rd and 4th chevrons trigger it, and eventually these go away too.
    - the energy meter shows the same amount of 'green' regen with the paddle, regardless of whether 1, 2, 3 or 4 chevrons. (Later, once the battery has been used a little, the degree of the energy meter green recovery increases with increasing chevrons steps.
    - most convincingly, because my brakes had sat a bit after being wet from rain, they had that thin layer of rust that makes a low grumbly/rubbing noise when initially activated. I heard this noise definitively while using only the paddles to decelerate, and stopped the noise by stepping the chevrons back down.

    Again, all of this only happens when the battery is nearly full. Once a few miles are driven off and the battery can accept a charge, the brake lights no longer come on with the paddle use, the brake noise ceased, and the green energy showing regen recovery stepped incrementally with each chevron increases.

    So, it seems rather than starting the engine to deal with excess energy from attempting to regen brake on a full battery, my car (2019 PHEV) instead simply uses the friction brakes in concert with a low and variable amount of regen recovery.

    I had not been expecting this and found it interesting to learn. Again, this may be old news...
    Kendalf and Fast Eddie B like this.
  9. gedwin

    gedwin Member

    To answer your question and to complement my post preceding this one, at no time did the engine come on. EV mode throughout.
  10. insightman

    insightman Well-Known Member

    Thanks! To my surprise, it appears that Honda decided to provide consistent paddle braking power when the battery is fully charged, even if it requires activating the mechanical brakes.

    I wonder why my Clarity sometimes (battery not fully charged) rejects the number of chevrons I select and, instead of activating the brakes, lowers the number of regen chevrons it is willing to grant?
    gedwin likes this.
  11. gedwin

    gedwin Member

    And for the record, my car surely does the same thing in rejecting 4 or even 3 chevrons at times. This did not happen in my testing yesterday on flat road - 4 chevrons were accepted with a full battery at that speed, but with the apparent application of friction brakes. I’ve noticed the “rejection” in the past mainly when going downhill with significant speed and a full battery. So, it may be a question of magnitude of the energy to be absorbed? I really don’t know, but is sure seems that there is some decision making going on by the car.

    I have not yet tested whether the rejection/flashing chevrons condition still triggers the brake light, but I will have opportunity to test that in the future and will report back. (I suspect it will.). This begs the question why it should reject at all, and not simply apply more friction braking? (If that is indeed what is happening as it seems to be.)

    Sent from my iPhone using Inside EVs
    insightman likes this.
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  13. David Towle

    David Towle Active Member

    On full braking, family cars nowadays can generate about 0.9 g. Sports cars can typically do 1.1 g or more.
    1 g = 32 ft/sec^2.
    0.9 g = 29 ft/sec^2 = 8.8 m/sec^2

    So the 0.7 m/sec^2 is less than 10% of full braking. I'm 100% sure the Clarity regen can do that much, probably with a maximum of at least 2.0.
  14. GaryClark

    GaryClark Member

    Regeneration needs to be able to store the energy so if fully charged you'll get very little regeneration if any and if none they you are just coasting and I'd expect the brake lights to no reflect you effectively coasting. As with any vehicle it's best to verify like many have, the characteristics of the vehicle they are in to make sure they are aware of indicators and when the friction brakes are automatically applied while in adaptive cruise if so equipped.

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