Droning Noise at Turn-off--- PHEV - Kia Niro Forum
 
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post #1 of 8 (permalink) Old 12-09-2018, 11:45 AM Thread Starter
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Droning Noise at Turn-off--- PHEV

When I turn off my 2018 PHEV after driving, I hear a 3 second low frequency droning noise (like the sound of an electric fuel pump). I am not certain, but I don't believe I heard it when it was new. Has anyone else heard and identified the sound source?
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post #2 of 8 (permalink) Old 12-09-2018, 07:46 PM
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Quote:
Originally Posted by Arthur View Post
When I turn off my 2018 PHEV after driving, I hear a 3 second low frequency droning noise (like the sound of an electric fuel pump). I am not certain, but I don't believe I heard it when it was new. Has anyone else heard and identified the sound source?
maybe. I hear something after I plug it in.

2018 Niro PHEV LX Silver/charcoal
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post #3 of 8 (permalink) Old 12-11-2018, 05:03 AM
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I hear the same noise after switching off - no idea as to the source!
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post #4 of 8 (permalink) Old 12-11-2018, 07:51 AM
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Originally Posted by Arthur View Post
When I turn off my 2018 PHEV after driving, I hear a 3 second low frequency droning noise (like the sound of an electric fuel pump). I am not certain, but I don't believe I heard it when it was new. Has anyone else heard and identified the sound source?
The hybrid system makes a bunch of noises according to the manual. If course it doesn't say what those noises are so it's not very helpful.

I've noticed it since we bought car in April, no big deal, just a feature. With the PHEV you can definitely hear that car setting up to charge the battery, probably some relays closing and the AC-DC converter starting up. On shutdown the reverse happens, with the inverter that provides the AC power to the motor turning off. A lot of high voltage / high power circuits make noises when starting or stopping. Has to do with high magnetic fields in the inductors in the switching power supplies and the high switching frequencies used. When the circuit starts or shuts off you can get brief resonances in those parts of the system that cause some noise.

I was curious about the voltage of the PHEV battery (360V as it turns out) and I found this Emergency Rescue Guide Manual for the Niro PHEV which is very interesting:

http://www.kia.ca/content/ownership/...ro-phev-en.pdf

So the car has to convert the incoming AC from the charger (120VAC or 220VAC) to 360VDC (a little more actually) at ~9A. That takes some serious switching circuitry including large capacitors and inductors. That system will definitely sing occasionally.
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post #5 of 8 (permalink) Old 12-11-2018, 12:53 PM
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There's also something called a VSS box, vehicle sound simulator. I'm thinking about unhooking mine and seeing what sounds it actually makes. Sounds stupid to be making the thing louder just because it's on electric. Unsure what stages of running/driving that it is engaged in though.
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post #6 of 8 (permalink) Old 12-12-2018, 08:32 AM
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There's also something called a VSS box, vehicle sound simulator. I'm thinking about unhooking mine and seeing what sounds it actually makes. Sounds stupid to be making the thing louder just because it's on electric. Unsure what stages of running/driving that it is engaged in though.
It's only active at low (meaning parking lot) speeds. It's designed to alert pedestrians that might not otherwise hear the stealthy hybrid.

Quote:
Originally Posted by The Owner's Manual
The Virtual Engine Sound System generates engine sound for pedestrians to hear vehicle sound because there is limited sound while electric motor power is used.
  • If the vehicle is moving at slow speed, the VESS will operate.
  • When the gear is shifted to R (Reverse), an additional warning sound will be heard.
I would think disconnecting it would open you up to some significant liability in the (unlikely) event you pummeled someone in a parking lot. If they said they never heard your car and it comes out that you deliberately disconnected a factory safety system I'm thinking it might not go so well for you in court.

Jim
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post #7 of 8 (permalink) Old 12-13-2018, 06:13 PM
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I hear it too, each time I turn off the car from EV mode - and my Niro PHEV is only a week and a half old. I don't think it's anything to worry about.
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post #8 of 8 (permalink) Old 12-15-2018, 10:45 PM
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Originally Posted by jmurphEV View Post
I would think disconnecting it would open you up to some significant liability in the (unlikely) event you pummeled someone in a parking lot. If they said they never heard your car and it comes out that you deliberately disconnected a factory safety system I'm thinking it might not go so well for you in court. [IMG class=inlineimg]/forum/images/KiaNiroForum/smilies/tango_face_surprise.png[/IMG]
Especially if they were visually impaired.
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