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2018 PHEV Brake Lunge and Regen braking occurs too late, panic braking hard

392 Views 10 Replies 6 Participants Last post by Ian W, 9 d ago

ican

Hello All:
Purchased my brand new 2019 KIA Niro PHEV in Dec. 2018; it has 45,000 Miles. The Tax credit was quite enticing when purchased.
I had one issue with Auxiliary battery that needed to be replaced about 24,000 miles on the odometer. Otherwise I'm pretty happy with my Kia Niro PHEV.

Current Issue:
1. The vehicle lunges when I tap the brakes gently at low speeds
2. In slow traffic (with adaptive cruise off, under 30 mph) the braking distance has increased with time, and I have noticed the proximity alarm goes off before I can apply the brakes hard/aggressively to bring the vehicle to a complete stop. It appears lately medium pressure on the brake pedal doesn't stop the vehicle. In contrast, I have to brake hard and aggressively for it it come to a stop. I feel the regen braking is delayed and the stopping distance has increased with as time has lapsed since purchase.
1. Is the regenerative brakes on the Front Wheels or Rear Wheel brakes or both?
2. How often do the brake pads/rotor needs to replaced, do they wear out like the brakes on the ICE vehicles?
3. Can I take the vehicle to a local Brake shop for trouble shooting or is regen brakes complicated enough that the vehicle needs a trained tech at Kia Dealer to inspect and troubleshoot?

Thanks in advance
Ican

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Steel188

· #2 · 12 d ago

When was your last service? What did the inspection report say about the condition of your brake pads and discs?

Whilst regen certainly increases their service life, brakes are a consumable item just like tyres and oil.

Also, when was your brake fluid last changed? It’s hygroscopic and should be changed in accordance with the service schedule for your country and use.

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sighttomtom

· #3 · 12 d ago

ican said:
Current Issue:
1. Is the regenerative brakes on the Front Wheels or Rear Wheel brakes or both?
2. How often do the brake pads/rotor needs to replaced, do they wear out like the brakes on the ICE vehicles?
3. Can I take the vehicle to a local Brake shop for trouble shooting or is regen brakes complicated enough that the vehicle needs a trained tech at Kia Dealer to inspect and troubleshoot?

Thanks in advance
Ican

"regen" has nothing to do with physical brakes but instead a generator resistance. think of as "engine braking". is this occurring in EV mode only [PHEV] and goes back to normal when in HEV mode? brake pads should last many times longer than a standard ICE vehicle. like one member noted, flush the brake fluid if it improves. for regen troubleshooting, you should really take it to a specialist or a dealer you trust as they will have machines specific to testing these type of issues.

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atc98092

· #4 · 12 d ago

ican said:
1. Is the regenerative brakes on the Front Wheels or Rear Wheel brakes or both?

Regen is only on the driven wheels, so front only.

ican said:
2. How often do the brake pads/rotor needs to replaced, do they wear out like the brakes on the ICE vehicles?

On a hybrid vehicle, brake pads usually last more than 100,000 miles without an issue. But everyone's driving conditions differ, so it's possible that under some conditions they would need replacing earlier.

ican said:
3. Can I take the vehicle to a local Brake shop for trouble shooting or is regen brakes complicated enough that the vehicle needs a trained tech at Kia Dealer to inspect and troubleshoot?

Regen doesn't use the brakes at all. There's nothing special about the brakes on your car that any competent repair shop can't handle.

As already mentioned, have the brake fluid flushed and changed, as yours is now approaching five years old and they can absorb moisture which could affect the system operation.

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Johnxyz

· #5 · 12 d ago (Edited)

I have a 2019 NIRO PHEV and never think about applying the brakes. I just press the pedal when necessary and the car does all the rest - just press the brakes naturally.

If your play with the brakes trying to treat it any differently than a normal car - you may be introducing operator error.

Our Niro has 50,000 miles on it now - I do the maintenance on it as I do on all our cars.

The front and rear brakes and well as the rotors have no noticeable wear.

A suggestion, in a parking lot driving safely with no other cars around - take the car out of drive, put it in neutral while it is moving and apply the brakes and see what happens. Is there any difference?

If you are noticing truly different behavior with the brakes get to a Dealer immediately and make sure you drive with the Advisor to show him what you are experiencing. Intermittent brake issues are very serious.

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Reactions: 3

ican

Discussion Starter · #6 · 11 d ago

sighttomtom said:
"regen" has nothing to do with physical brakes but instead a generator resistance. think of as "engine braking". is this occurring in EV mode only [PHEV] and goes back to normal when in HEV mode? brake pads should last many times longer than a standard ICE vehicle. like one member noted, flush the brake fluid if it improves. for regen troubleshooting, you should really take it to a specialist or a dealer you trust as they will have machines specific to testing these type of issues.

Thank you, for your insight and your well thought out response, appreciate it much. My best bet is to take the car to the dealer and have them flush the fluid, and see if they did flush the brakes the last time I took it to them.

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ican

Discussion Starter · #7 · 11 d ago

Johnxyz said:
I have a 2019 NIRO PHEV and never think about applying the brakes. I just press the pedal when necessary and the car does all the rest - just press the brakes naturally.

If your play with the brakes trying to treat it any differently than a normal car - you may be introducing operator error.

Our Niro has 50,000 miles on it now - I do the maintenance on it as I do on all our cars.

The front and rear brakes and well as the rotors have no noticeable wear.

A suggestion, in a parking lot driving safely with no other cars around - take the car out of drive, put it in neutral while it is moving and apply the brakes and see what happens. Is there any difference?

If you are noticing truly different behavior with the brakes get to a Dealer immediately and make sure you drive with the Advisor to show him what you are experiencing. Intermittent brake issues are very serious.

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ican

Discussion Starter · #8 · 10 d ago

Johnxyz said:
I have a 2019 NIRO PHEV and never think about applying the brakes. I just press the pedal when necessary and the car does all the rest - just press the brakes naturally.

If your play with the brakes trying to treat it any differently than a normal car - you may be introducing operator error.

Our Niro has 50,000 miles on it now - I do the maintenance on it as I do on all our cars.

The front and rear brakes and well as the rotors have no noticeable wear.

A suggestion, in a parking lot driving safely with no other cars around - take the car out of drive, put it in neutral while it is moving and apply the brakes and see what happens. Is there any difference?

If you are noticing truly different behavior with the brakes get to a Dealer immediately and make sure you drive with the Advisor to show him what you are experiencing. Intermittent brake issues are very serious.

Appreciate your response, it good idea like you mentioned testing the brakes with neutral. TY

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Ian W

· #9 · 10 d ago

I've always wondered about how regen is blended with pad-on-rotor friction during braking in our PHEV. It seems that under light braking the regen does it all, but beyond a certain about of pedal pressure friction quickly gets involved and the car really decelerates much harder.

Can anyone explain how that combination of braking is actively managed, and how, if at all, it complicates brake maintenance?

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atc98092

· #10 · 10 d ago

Ian W said:
I've always wondered about how regen is blended with pad-on-rotor friction during braking in our PHEV. It seems that under light braking the regen does it all, but beyond a certain about of pedal pressure friction quickly gets involved and the car really decelerates much harder.

Can anyone explain how that combination of braking is actively managed, and how, if at all, it complicates brake maintenance?

Your perception is accurate. Initial application of the brake pedal only activates regen, with no friction brakes applied. As you press harder on the brake, the computer determines if you are requesting more braking power than regen can supply. Remember that the amount of regen available varies by vehicle speed and other factors, such as the power capabilities of the EV motor. In your case, the EV motor is only about 45kW, and won't provide even that level of regen power. It will likely top out around 30kW. That level of regen isn't all that strong (it's reasonable, but not super powerful), so moderate or higher braking demand will activate the friction brakes. My Bolt would display the amount of regen flowing into the battery. At freeway speeds and hard braking, I could see as much as 80kW, and that's with a 150kW EV motor.

Regen does not complicate the friction brakes in any way, because they are not involved with regen. It's all done in the EV motor and control system. The brakes on a hybrid or EV are basically the same mechanically to a car with an ICE engine. There's some computer interfacing between the brake pedal and the actual hydraulic pressure application, but that in no way impacts servicing the friction brake system. All regen does is make the brake pads/shoes last far longer than in a car without regen.

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Reactions: 2

Ian W

· #11 · 9 d ago

Thanks, Dan. Excellent explanation. That fits with my experience in that if I "hit" the brake pedal, even without continuing to press down harder, that initial hit must trigger the friction brakes on the assumption that I'm intending to brake hard and there is no time for messing around waiting to see how hard I continue to press before getting the friction brakes involved. And I like how the friction brakes are the same old reliable design.

Respectfully getting back to the OP's question: I was wondering if that friction braking engagement I have noticed when "hitting" the pedal is related to (is?) the "lunging". (However, anything unexpected I have experienced about braking is always more braking, not less!)

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