Regen braking stuck at 2 chevron, video attached

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Al-clarity

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Hello
Drove from Lake Tahoe to SF Bay Area today. The drive started 28F and a lot of down hills. I noticed that I can not increase the regen braking pass 2. It would flash the 3rd chevron but remain at 2. The regen meter only went downward matching what 2 chevron would provide. Hitting brake paddle would not increase regen meter, probably using real brake.
Eventually when i reached to lower elevation I was able to increase to 3 and 4. No other warning that I noticed. anyone experienced this or have an explanation or theory to share?
 

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If mostly downhill it probably just got too hot and regen was restricted to prevent battery damage. I’ve had it happen to me a few times coming down long mountain passes and using a lot of regen. Once it cools down it goes back to working normal.
 
craze1cars said:
If mostly downhill it probably just got too hot and regen was restricted to prevent battery damage. I’ve had it happen to me a few times coming down long mountain passes and using a lot of regen. Once it cools down it goes back to working normal.
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Well I am glad I am not alone.

This happens at beginning of the downhill and temperature was 28f to 33f as what shows in the video. I can gradually increase the chevron as further going down hill to lower altitudes and warmer weather. I was able to set to 3 chevrons around 44F about 15min -20min after video was taken.
It almost feel like it’s too cold to regen brake.
 
Remember, it’s not the ambient temperature that matters the most; it’s the battery pack temperature. (And possibly the trend in battery pack temperature since it’s possible that this could be a trigger in the software.) But I believe that you are on the right track in so much as I think that cold Li-ion batteries can not hold or accept/deliver as much power as warmer ones. Or it could be as @craze1cars theorizes that the battery pack was close to overheating. Without real time OBD measurements, we’ll never know.
The BMS is most certainly set by Honda to protect the battery health at all times or they would go bankrupt with warranty claims.
What we all wouldn’t give for Honda to tell us how all this is set up to work!
 
The attach map shows when the video is taken. The blue line is uphill and orange is the downhill. It could not have been more than 5 miles of downhill . I pretty much noticed right away since it didn’t provide the expected resistance. I tried to change all different setting before taking the video.

If overheat is reason, is it possible that the uphill climb where HV mode used generated heat? It was quite a steep hill.
 

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  • 552530E1-5B09-4A88-9A8F-23BA7E69C30E.webp
    552530E1-5B09-4A88-9A8F-23BA7E69C30E.webp
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Al-clarity said:
I noticed that I can not increase the regen braking pass 2. It would flash the 3rd chevron but remain at 2.
Click to expand...
Did this problem persist regardless of the speed you were traveling? My Clarity has rejected chevrons at expressway speeds, but not after I got off the expressway a minute later.
 
I believe the regen is speed limited. There are many situations when my Clarity won't allow the top level of regen such as exiting a freeway and just wanting to slow down/regen while on the offramp.

For long downhill trips I use ACC which automatically manages downhill speed. However any EV or PHEV car will reach a point when the battery is fully charged and regen is no longer available.
 
Speed didn’t matter in my case. It was varying 60-0 mph.
I never noticed this and frequently use it to slow down from highway off ramp. Not going to call it an problem. Just something new to me. And a bit bummed that i can’t recover all those lost kinetic energy.
 
To be fair I haven’t watched your video I can’t make it work...just talking in generalities. I suppose it could be temp on the cold side as well as the hot side. Batteries need to be at a certain temp to accept fast charge safely, and if you’re outside of a certain parameter the car is programmed to restrict the speed of the charge it will dump into the battery via regen. Too cold, too hot, speed too high, state of charge too high...I can see and have seen any of these things occur that cause regen to be restricted. Then it comes back when all parameters are met. I’m quite certain car is doing what it is programmed to do.
 
jdonalds said:
I believe the regen is speed limited. There are many situations when my Clarity won't allow the top level of regen such as exiting a freeway and just wanting to slow down/regen while on the offramp.

For long downhill trips I use ACC which automatically manages downhill speed. However any EV or PHEV car will reach a point when the battery is fully charged and regen is no longer available.
Click to expand...

I have noticed that typically you’re limited to three Chevron at speeds above 55 mph and 2 Chevron’s above about 80. Of course if you have a full battery or your battery temp is too cold or hot then that all goes out the window.


Sent from my iPhone using Inside EVs
 
You may be able to reclaim more regen in SPORT mode, assuming you were in ECON or NORMAL modes.

upload_2019-10-28_17-46-24.webp

This regen deceleration graph was for another Honda car, but employing the similar iMMD drivetrain.

Also, if the circumstances arise again you can try using cruise control to see if it reclaims more energy. If find at times that regen will be pretty mild, but by engaging the CC at a lower speed (say ~3-4 mph below my current speed), the power meter will be much more into the green and I can feel the deceleration more acutely. But I believe it may also engage the friction brakes, but haven't tried to experiment with it to know for sure.
 
I tried setting to sport mode and did not get more regen out of it. Seems like the regen ability was limit to what 2 chevrons would give you. Didn’t try cc as it was twisty mountain road with speed changes.

Anyone had experience setting regen at 32F or below? I am curious to know if it tends to happen more. I live in SF Bay Area and it never get that cold. This is the first time the car being in sub 32F.
 
It has happened to me regularly in some steep downhill freeway that it limits me to 3 chevrons and flashes at the fourth when I try to increase regen further, irrespective to the battery level but it never has stuck on two.
 
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