Weird/dangerous ACC/regen braking behavior

[Esprit1st]

From what I see here the rear brakes are strictly hydraulic while the fronts are additionally software controlled by a ball screw applying pressure in the cylinder. My guess is #7 is a valve to bypass the motor input and apply hydraulic upon emergency type activation.
Thanks so much for the diagram ( outdated 1990 engineer speculation approved)

That would make sense since we don't have a second motor in the back [emoji12]. Unless they come out with a dual motor option ... [emoji6]

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[XtsKonaTrooper]

Its because most of the ppl at the dealers or management, havent h true clue about the features . Its pretty well the engineers/designers and us, as the early adopters (EV Pioneers).

It's crazy. We're so familiar with how ice cars work but we know so little about EVs. It's sad that the companies don't explain these things. Quite frustrating for our curious minds.

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[Gjpzee]

I just experienced something weird and dangerous.

Radar cruise control was on and i was getting of the highway and traffic was slowing down to a light. I was in eco mode with level 3 regen selected. Battery was at 30% charge.

The car started to decelerate and then suddenly the regen went away and car was coasting.

I had to slam on the brake to stop and while i was braking the car was still coasting, no regen and braking was with mechanical brakes. The power display was not showing any regen.

And the braking was not very strong. The force i felt was lower than the force I feel from level 3 regen.

No error message was shown l, blue link diagnostic showed no problems.

The regen came back after i left from the stop light, without me doing anything special.

Anyone else experience something similar?

It's the first time it happens to me

Something similar happened to me today. I was on regen 2 or 3 while slowly turning around in a parking lot. Suddenly the regen went off and the car coasted ahead, I had to slam the brakes to stop the car. I tried to replicate it but was not able to.

 

[electriceddy]

Something similar happened to me today. I was on regen 2 or 3 while slowly turning around in a parking lot. Suddenly the regen went off and the car coasted ahead, I had to slam the brakes to stop the car. I tried to replicate it but was not able to.

I hope this does't develop into a new rash of problems, we have enough already! Keep us posted, BTW what was the 12V accessory battery voltage (if you have a meter)

 

[victor_2019]

I also have a Honda clarity

now the honda clarity unfortunately doesn't have the strong regen capability of the kona and it uses blended braking all the time, but you can feel the difference in braking force when the regen braking is not possible.

when applying the brake with a discharged battery there is a mix of regen and friction braking and you get a specific level of deceleration for a specific brake pedal pressure.

however when the battery is fully charged, no regen is possible. at this point when pressing the brake pedal you only get friction brakes, and you can tell that for the same level of pedal force the braking of the car is a lot more sluggish.

and this is exactly the sensation I felt when I pushed on the brake that day, for the same level of brake pedal force, with missing regen, the braking was a lot more sluggish than I was expecting. The only question is why the hell my regen disappeared momentarily.

I tried to reproduce this with a fully charged battery but it seems the kona always allows some level of regen even with a "full" battery, unlike the clarity. (meaning the "100%" battery level on the kona probably has more margin than on the clarity and they don't disable regen immediately). So the braking was normal.

 

[Esprit1st]

Something similar happened to me today. I was on regen 2 or 3 while slowly turning around in a parking lot. Suddenly the regen went off and the car coasted ahead, I had to slam the brakes to stop the car. I tried to replicate it but was not able to.

Are you sure you didn't touch the paddle accidentally? [emoji2369]

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[Gjpzee]

Are you sure you didn't touch the paddle accidentally?

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I do not recall using the left paddle, but I use it frequently so it could be possible I sub consciously pressed it to slow the car.

 

[Gjpzee]

I hope this does't develop into a new rash of problems, we have enough already! Keep us posted, BTW what was the 12V accessory battery voltage (if you have a meter)

I have a multimeter but I charged the car overnight and drove a bit today so i guess it's too late. But just curious what could be the relationship between regen failing and the 12v battery? Wouldn't regen be using the main battery?

 

[electriceddy]

I have a multimeter but I charged the car overnight and drove a bit today so i guess it's too late. But just curious what could be the relationship between regen failing and the 12v battery? Wouldn't regen be using the main battery?

Just thinking software glitches, possible command issues to the brake cylinder hydraulics.

 

[Wildeyed]

Something similar happened to me today. I was on regen 2 or 3 while slowly turning around in a parking lot. Suddenly the regen went off and the car coasted ahead, I had to slam the brakes to stop the car. I tried to replicate it but was not able to.

 

[Wildeyed]

Run the onboard diagnostics.

 

[Gjpzee]

Run the onboard diagnostics.

Bluelink showed everything as normal. Can we run diagnostics from the car dash settings?

 

[Wildeyed]

Bluelink showed everything as normal. Can we run diagnostics from the car dash settings?

As far as I know the onboard diagnostics are accessed through the BL icon and is the same thing as the remote (phone based)BL diagnostics.

 

[nigels]

I do not recall using the left paddle, but I use it frequently so it could be possible I sub consciously pressed it to slow the car.

OK, help me out here. Why would holding the left paddle not cause deceleration due to regeneration? I’ve experienced left paddle not slowing the car down and I’m trying to understand whether that’s normal or not. This post made me think I have my mental model of how the left paddle works wrong.

 

[victor_2019]

OK, help me out here. Why would holding the left paddle not cause deceleration due to regeneration? I’ve experienced left paddle not slowing the car down and I’m trying to understand whether that’s normal or not. This post made me think I have my mental model of how the left paddle works wrong.

two reasons:

1 - the battery is really full and regen not possible anymore. the dash should display a warning

2 - there is a software glitch in the car's computer. my regen temporarily disappeared when I was pressing brake pedal, not the left steering wheel paddle.

 

[Gjpzee]

I wonder is there is a perfect storm of events that cause this to happen. I was at slow speed, maybe 5mph, on regen 2 or 3 and braking at the same time. What is don't remember is if I used the left paddle or not. I was shaken after the regen was lost and had to react reflexively by slamming the brakes which skidded the car to a stop.

 

[KonaTom]

I wonder is there is a perfect storm of events that cause this to happen. I was at slow speed, maybe 5mph, on regen 2 or 3 and braking at the same time. What is don't remember is if I used the left paddle or not. I was shaken after the regen was lost and had to react reflexively by slamming the brakes which skidded the car to a stop.

regen cuts off around 5mph. Many people have experienced this thinking the car surges ahead while braking, but it is just the regen cutting off and you need to press the brake to stop, or hold the left paddle to come to a stop. I wish the regen would continue right to a stop for true one pedal driving, without having to hold the left paddle.

 

[nigels]

regen cuts off around 5mph. Many people have experienced this thinking the car surges ahead while braking, but it is just the regen cutting off and you need to press the brake to stop, or hold the left paddle to come to a stop. I wish the regen would continue right to a stop for true one pedal driving, without having to hold the left paddle.

This makes sense. Thanks, @KonaTom. In my case, I was approaching a junction quite slowly while going down an incline. Auto regen was slowing the car, but not enough to stop me at the intersection, but when I pulled the left paddle to slow to a stop it felt as if I'd gone into neutral in a manual transmission car. The car accelerated towards the junction and I had to quickly brake. Given that the brake pedal integrates regen and friction braking so seamlessly, I'm not sure I'll bother with playing the will-it-stop-in-time guessing game with the left paddle now.

 

[Gjpzee]

regen cuts off around 5mph. Many people have experienced this thinking the car surges ahead while braking, but it is just the regen cutting off and you need to press the brake to stop, or hold the left paddle to come to a stop. I wish the regen would continue right to a stop for true one pedal driving, without having to hold the left paddle.

This makes sense, however I was not able to replicate it. I'll try and see if I can replicate it in an empty parking lot at a speed less than 5mph.

 

[JSU]

As I read all three pages of this conversation, I was wondering how the Kona's regen handles loss of traction. In my old i3, if the drive wheels (rear on the i3) lost traction even for a millisecond (like due to loose sand on the road, or some rough road surfaces), the regen would cut out 100%. Since in the i3, you can't shut off or vary the level the regen yourself, it had this safety feature to prevent wheel lockups. So i3 drivers are trained to always be ready to pounce on that friction brake if this type of situation occurs. I did need to slow down more quickly than I thought recently when my kona hit some rough road at an intersection where a car pulled out too early in front of me. I let off the accelerator expecting the initial slow down from the Kona's regen (set to 3) but it just wan't there, so I had to quickly apply the friction brakes. But I do believe I may had lost traction on that initial full off the pedal Level3 regen.

Does anyone know if this feature of the regen cut off is something also found in the Kona electric? I'm sure I will find out when I can play in the snow once Winter comes.