techumper
Posts: 4
Joined: Sat Mar 01, 2014 8:30 am
Location: Central Cali

Re: Possible Regen Brake Issue

Tue Apr 08, 2014 3:58 pm

nozferatu wrote:
Skullbearer wrote:Definitely not a normal sound or feel, but it probably is related to the blended braking system.

You can replicate the 'correct' sound of this change by using moderate regen braking at speed (say 45mph) and then shifting to N. The vehicle makes a very slightly clunky transition to 100% hydraulic brakes, but has almost identical feel after transition. The sound and feel are not nearly so severe that they would cause alarm, and everyone should do it at least a couple of times to know what's 'normal' (I did it on accident the first time). Blended braking is a very difficult process to manage, both mechanically and software wise, so I think Chevy did a fantastic job with it so far. The vehicle makes the transition gradually from some set speed during normal continuous braking... usually from around 6mph down to 2 or 3 mph. Reliable and efficient torque control in a PMAC motor begins to become very difficult at very low speeds and can cause a jerky braking feel, so the transition to hydraulic braking keeps it smooth. On your problem it either has to be a bad controller, bad electrical connection, or most likely a bad blended braking system (the electro-mechanical portion, which may be a solenoid or other proportional valve inline with the master cylinder output, or even the master cylinder itself). I don't know what unit Chevy used, but Bosch recently began selling a production blended braking unit that acts as the master cylinder and provides the same feel as if you are actually braking, but controls the actual pressure output to the brake system. The Bosch unit is the only 'off-the-shelf' system that could do the blended braking style that the Spark has, so I'll be it's what we'll find in our vehicles. Given that it's a very new product, we should all keep an eye out for failures... worst case though, the system 'should' fault to an open bypass state... ie 100% hydraulic brakes.

If your dealer is having trouble diagnosing it, they should start by checking the wiring harness to the blended brake unit, then replacing the unit itself, and finally with a controller replacement. If it starts happening above 6mph, pay attention to whether or not the electric power meter suddenly goes to no regen even though you're braking, it could be falsely detecting an N position on the shifter.
Hey Skullbearer,

Thanks for the input. It's a bit disconcerting that the dealership has only ONE certified tech on hand for the Spark EV..which makes me concerned to be honest. But I hope it's an easy fix and they don't have to tear the car apart.

I also get the sense that it may be a bad electrical connection because as I said earlier, I hear a faint but definite variable pitch electrical "circuit" type sound emanating from the front wheel arches/areas...while in P or N.

I've actually forwarded this posting you wrote above to the shop foreman as I think it's a great starting point for them.

My problem is definitely most noticeable at low speeds...5 MPH and below...with perhaps coming to a stop or in N or P allowing the problem to be most noticeable. It's quite loud...the twanging and clicking. And when coming to a stop, the transition feels like there's a grinding feel.
I have the same symptoms happen to me especially in stop and go situations and where traffic is constantly moving between 5 and 0 mph. I never associated it with an issue, since the braking system on the spark is different from conventional setups.

I also do hear the same circuit board noise that you heard while in the garage, I figured that it was 'thinking' - even while OFF. It immediately stopped after pressing the lock button on the key fob. just my experience in the last 2 months.

nozferatu
Posts: 575
Joined: Sat Feb 01, 2014 4:47 pm

Re: Possible Regen Brake Issue

Tue Apr 08, 2014 4:18 pm

Guys,

I took the liberty of recording the sounds via both video and audio using my phone....

The first audio clips are from the front engine bay...hood up...to the left and right of the Chevy cover. This is the electrical sound (almost like arching or welding) I was talking about....car can be either in N or P...please excuse the movements.

https://www.dropbox.com/s/2kgsu4yoni7489q/VIDEO0011.3gp

The second clip is the sound of the brakes...first in N...then I shifted to P and did it again about half way through. You can clearly hear the hydraulic pump coming on and off....and at about 29 seconds I shift into P and do it again.

https://www.dropbox.com/s/rxwdkyt84vtke1m/VIDEO0012.3gp

Let me know what you think...you can clearly hear the twang...like a wire being plucked.

The dealer was useless...they didn't even hook up the car to anything nor did they drive it...essentially it sat there and they said it's normal. Can I escalate this at Chevy? This may be a serious issue electrically.

Cheers.
Last edited by nozferatu on Wed Apr 09, 2014 7:58 am, edited 1 time in total.

bespoke
Posts: 8
Joined: Wed Jan 22, 2014 5:25 am

Re: Possible Regen Brake Issue

Tue Apr 08, 2014 4:38 pm

There is a clear description of what you are hearing on page 9-25 of the Owners Manual:

The braking system is computer controlled and blends the regenerative braking with the conventional hydraulic disc brakes to meet any requirements for deceleration. The controller interprets the braking request and uses regenerative braking, conventional hydraulic braking, or a combination of both as necessary. Because the controller applies the hydraulic brakes through its high pressure accumulator, you may occasionally hear the motor‐driven pump when it recharges the system. This is normal.
Last edited by bespoke on Tue Apr 08, 2014 4:40 pm, edited 1 time in total.

nozferatu
Posts: 575
Joined: Sat Feb 01, 2014 4:47 pm

Re: Possible Regen Brake Issue

Tue Apr 08, 2014 4:39 pm

bespoke wrote:There is a clear description of what you are hearing on page 9-25 of the Owners Manual:

The braking system is computer controlled and blends the regenerative braking with the conventional hydraulic disc brakes to meet any requirements for deceleration. The controller interprets the braking request and uses regenerative braking, conventional hydraulic braking, or a combination of both as necessary. Because the controller applies the hydraulic brakes through its high pressure accumulator, you may occasionally hear the motor‐driven pump when it recharges the system. This is normal.
Yes...that part is normal...the rest is not IMO. I think you are referring to what sounds like a duck...that's not what I'm referring to.

nozferatu
Posts: 575
Joined: Sat Feb 01, 2014 4:47 pm

Re: Possible Regen Brake Issue

Wed Apr 09, 2014 8:27 am

Bump...

Anyone else listen to those videos?

Any further opinions? I'm going to take my car to another dealer...this one was useless...they opened up a TAC req but since they didn't fully describe the issues, TAC says it's normal and thought my parking brake is on..>WTF is wrong with these people?

StevesWeb
Posts: 147
Joined: Tue Jan 07, 2014 5:36 pm

Re: Possible Regen Brake Issue

Thu Apr 10, 2014 6:00 am

nozferatu wrote:Bump...

Anyone else listen to those videos?

Any further opinions? I'm going to take my car to another dealer...this one was useless...they opened up a TAC req but since they didn't fully describe the issues, TAC says it's normal and thought my parking brake is on..>WTF is wrong with these people?
I sometimes hear similar sounds from my Spark EV and I have attributed it to the ABS system, these cars are so thoroughly computerized that I expect any serious issue would be detected by the onboard diagnostics during POST.

A Spark EV is essentially a computer with nice wheels, a ginormous battery, and the most wonderful electric motor ever made. Hymns should be written singing the praise of these motors.

My advice:
  • Be happy
  • Don't worry
What you have done is bought a wonderful, amazing car.

Skullbearer
Posts: 25
Joined: Sat Mar 15, 2014 6:47 pm
Location: Sacramento, CA

Re: Possible Regen Brake Issue

Thu Apr 10, 2014 8:12 am

I listened to the videos and compared to my own Spark. The clicking sounds like the system opening and closing the proportional valve or solenoid that allows direct pedal braking. The electrical noise may be the pump repressurizing the hydraulic accumulator, buy it doesn't sound like an arc to me (but hard to tell from cell phone audio)


Definitely a problem with the blended braking system.
Development Engineer
EVs, PHEVs, CVTs, ECVTs (Don't know it, look it up!)

High Voltage and Low Voltage;
They both bite, but only one is a funny story. Don't mess with the orange.

Skullbearer
Posts: 25
Joined: Sat Mar 15, 2014 6:47 pm
Location: Sacramento, CA

Re: Possible Regen Brake Issue

Thu Apr 10, 2014 8:15 am

If the next dealer is unreceptive, message me the contact info of the service writer. You can let them know an Engineer was consulted and will call. Let's avoid it though if they will handle it appropriately.

You can also use OnStar to get to Chevy Spark EV support, which can escalate it to Chevy Engineering.
Development Engineer
EVs, PHEVs, CVTs, ECVTs (Don't know it, look it up!)

High Voltage and Low Voltage;
They both bite, but only one is a funny story. Don't mess with the orange.

nozferatu
Posts: 575
Joined: Sat Feb 01, 2014 4:47 pm

Re: Possible Regen Brake Issue

Thu Apr 10, 2014 2:07 pm

Skullbearer wrote:If the next dealer is unreceptive, message me the contact info of the service writer. You can let them know an Engineer was consulted and will call. Let's avoid it though if they will handle it appropriately.

You can also use OnStar to get to Chevy Spark EV support, which can escalate it to Chevy Engineering.
Hey man sounds great! Thanks for your effort and offer to call them. Let me see what they do and say. I doubt they'll do squat and I'm at the end of my fray to be honest in dealing with them. I'll keep you posted.

Cheers

nozferatu
Posts: 575
Joined: Sat Feb 01, 2014 4:47 pm

Re: Possible Regen Brake Issue

Thu Apr 10, 2014 2:08 pm

StevesWeb wrote:
nozferatu wrote:Bump...

Anyone else listen to those videos?

Any further opinions? I'm going to take my car to another dealer...this one was useless...they opened up a TAC req but since they didn't fully describe the issues, TAC says it's normal and thought my parking brake is on..>WTF is wrong with these people?
I sometimes hear similar sounds from my Spark EV and I have attributed it to the ABS system, these cars are so thoroughly computerized that I expect any serious issue would be detected by the onboard diagnostics during POST.

A Spark EV is essentially a computer with nice wheels, a ginormous battery, and the most wonderful electric motor ever made. Hymns should be written singing the praise of these motors.

My advice:
  • Be happy
  • Don't worry
What you have done is bought a wonderful, amazing car.
I agree...I'm just going to enjoy it. If it explodes, it's on them...I posted the videos on Youtube as well so that will get Chevy's attention hopefully.

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