Sudden acceleration after braking

[Gsbrryprk8]

I have an 8 month old SEL and was driving this morning at about 70 mph. I gently applied the brakes to slow for an exit, and when I lifted my foot from the brake pedal (maybe at 30-40 mph) the car momentarily accelerated forward requiring me to hit the brake again. It lasted well under a second and ended the moment the brakes were reapplied. I then exited the highway and returned home without incident.

This was most definitely NOT simply a feeling of coasting after deceleration. There was *definite* acceleration. I’ve driven it enough to recognize and be very familiar with normal braking behavior. Thoughts?

Details: Kona SEL 4058 miles, SOC 58%, ECO mode with level 3 regen. Outside temp 85F+, cabin AC on low.



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[Ronny]

I have an 8 month old SEL and was driving this morning at about 70 mph. I gently applied the brakes to slow for an exit, and when I lifted my foot from the brake pedal (maybe at 30-40 mph) the car momentarily accelerated forward requiring me to hit the brake again. It lasted well under a second and ended the moment the brakes were reapplied. I then exited the highway and returned home without incident.

This was most definitely NOT simply a feeling of coasting after deceleration. There was *definite* acceleration. I’ve driven it enough to recognize and be very familiar with normal braking behavior. Thoughts?

Details: Kona SEL 4058 miles, SOC 58%, ECO mode with level 3 regen. Outside temp 85F+, cabin AC on low.



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I presume you did not have cruise control on.

 

[Gsbrryprk8]

Correct: No cruise control.


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[electriceddy]

I have an 8 month old SEL and was driving this morning at about 70 mph. I gently applied the brakes to slow for an exit, and when I lifted my foot from the brake pedal (maybe at 30-40 mph) the car momentarily accelerated forward requiring me to hit the brake again. It lasted well under a second and ended the moment the brakes were reapplied. I then exited the highway and returned home without incident.

This was most definitely NOT simply a feeling of coasting after deceleration. There was *definite* acceleration. I’ve driven it enough to recognize and be very familiar with normal braking behavior. Thoughts?

Details: Kona SEL 4058 miles, SOC 58%, ECO mode with level 3 regen. Outside temp 85F+, cabin AC on low.



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Are you able to reproduce it? I was going to mention that I have encountered the regen loosing its previous setting and lowering itself on occasion
https://insideevsforum.com/community/index.php?threads/small-issues-quirks.5006/page-19#post-73645
which catches me by surprise, but that does not sound like the issue you might have encountered.
Also note that when this happens it lowers all modes not just ECCO.

 

[hobbit]

You probably hit a bump at just the wrong time, causing blended regen to "give up"
and fall to hydraulics. I've felt similar events, but am always ready for it since I know
what happens in these systems.

Let's avoid getting into another one of these... [see section 3]

_H*

 

[Gsbrryprk8]

Are you able to reproduce it?

I haven’t driven much since, but not so far.

You probably hit a bump at just the wrong time, causing blended regen to "give up"
and fall to hydraulics.

I don’t recall a bump or pothole there, and certainly will check next time. I’ve driven that route before and had no problem. Again, I had just let off the brake, and know what loss of deceleration feels like. This was (certainly felt like) a momentary actual acceleration. Unlike the Prius situation referenced, I believe I was no longer braking, though I can’t be sure. Regardless, it was alarming and I’m glad there wasn’t a vehicle in front of me.


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[Wildeyed]

A change from braking to regen might feel like acceleration. And any subsequent downshift of regen (from 1 to O, for example) could also feel like you've sped up. Just spitballing.

 

[RandallScott]

Because the Kona EV on 0 regen has very low rolling resistance the car doesn't behave like an ICE car when braking and releasing. An ICE car has a lot of driveline drag so when you let off the brake the car just keeps slowing, but with no regen applied the Kona WANTS to coast, so coming off the brake will feel like acceleration.
Most of the time I use only the paddles to stop and depending on how I'm driving I might be high-speed coasting with 0 regen, when I approach the stop I tap in 1, then 2, 3, then a full pull to stop. When stopping using the paddle, the car will not roll when the paddle is released. When stopping using the foot brake the car WILL roll when the brake is released just like an ICE car which makes using the brake better for slow-moving stop-n-go where you let off and the car rolls forward.

 

[ericy]

I have this vague recollection that I encountered something similar, but I don't recall what else was happening at the time. For all I know, I might have inadverently reactivated cruise control.

 

[R P]

You can get a sudden acceleration while on cruise control following someone that then moves out of your lane. Same with following someone on sharp switchback corners (common on mountain roads) when it temporarily loses sight of the car in front. But all this is normal and you just have to adapt/anticipate these situations.

 

[Wildeyed]

I have this vague recollection that I encountered something similar, but I don't recall what else was happening at the time. For all I know, I might have inadverently reactivated cruise control.

I know I've inadvertently clipped the cruise control "set" toggle with my thumb before. That'll cause the afterburners to kick in when you least expect it!

 

[Gsbrryprk8]

You probably hit a bump at just the wrong time, causing blended regen to "give up"
and fall to hydraulics.

I drove that same route yesterday and paid close attention this time. There is indeed a small bump right around where that happened so you maybe right. I couldn’t reproduce the issue though. I’ll be more vigilant from now on.


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[KiwiME]

Ok, now I know what you're referring to - there's a bump heading into a roundabout in the next town and I get the same effect; the car seems to jump forward momentarily while I'm on the brakes. My previous ICE cars have acted similarly on the same bump, almost like the ABS kicks in for a moment.