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Sonata strange battery charging behavior #4594405
12/04/17 08:18 PM
12/04/17 08:18 PM
Joined: Feb 2013
Posts: 11,100
Phoenix, AZ
Nick1994 Offline OP
Nick1994  Offline OP
Joined: Feb 2013
Posts: 11,100
Phoenix, AZ
I've always noticed that while braking/coasting my hvac fan blows a little harder than it does at idle. Didn't think much of it all year but I have a volt meter thing that plugs into the 12v outlet so I plugged it in.

While driving down the road with any amount of throttle, the voltage is in the low 12's, sometimes dips into the 11's. When coasting to a light or in traffic, or when braking, the voltage shoots up into the 14V range. At idle it goes back down into the 12's. I've also observed that with the headlights on my voltage goes up.

I put in a new battery in October, I don't have any issues. It starts fine and everything works. I was as just curious about this behavior. I left the volt meter in the 12V outlet for a week and glanced at it every now and then, same results. It's almost like a hybrid!

I'm guessing this is new car technology or something? About a month ago I hooked up my Solar Prologix PL2310 charger and it said it was 100%. When I go back to the car but don't start it, the voltage is around 12.7V.

I have 3 videos below. #1 is driving on the freeway. Sometimes with my foot on the gas, sometimes coasting. Voltage up when coasting, voltage down when accelerating. #2 is starting the car at a light. Voltage at startup is always above 14V. I then took off from the light and stopped at the next one shortly. I then revved the car in neutral. #3 is in a parking garage with me turning the headlights on and off. voltage up with lights on. voltage down with lights off.







2015 Hyundai Sonata 2.4L 89k Motorcraft Synthetic Blend 5w30 & OEM
2000 Toyota Camry 2.2L 231k Valvoline 5w30 & Fram Ultra
1996 Jeep Cherokee 4.0L 147k Mobil 1 HM 10w40 & Fram Ultra
Re: Sonata strange battery charging behavior [Re: Nick1994] #4594417
12/04/17 08:33 PM
12/04/17 08:33 PM
Joined: Jun 2003
Posts: 33,592
ME
eljefino Offline
eljefino  Offline
Joined: Jun 2003
Posts: 33,592
ME
I suspect your suspicions are accurate.

BMW has a car that only charges when braking, and the dealer gives complimentary batteries b/c to recode the computer to charge more would be an EPA/ MPG violation.

Re: Sonata strange battery charging behavior [Re: Nick1994] #4594431
12/04/17 08:39 PM
12/04/17 08:39 PM
Joined: Nov 2017
Posts: 382
North of you Idaho
KneeGrinder Offline
KneeGrinder  Offline
Joined: Nov 2017
Posts: 382
North of you Idaho
Is the Sonata a Hybrid?

It's almost like a hybrid!

I guess not! lol! I would take it to the dealer since you should have hyundai's 100,000 mile warranty. The voltage should be much more stable, and much more around 14.0 to 14.3 almost all the time.

Last edited by KneeGrinder; 12/04/17 08:46 PM.

08 Tribeca 86k PUP 5w30 wix
06 Accord Hybrid 134k PPHM 0w20 wix
02 Chevy k3500 99k Delvac 1 esp 5w40 wix
00 F350 136k Delvac 1300 15w40 wix
Re: Sonata strange battery charging behavior [Re: Nick1994] #4594432
12/04/17 08:40 PM
12/04/17 08:40 PM
Joined: Aug 2008
Posts: 21,314
ON, Canada eh?
StevieC Offline
StevieC  Offline
Joined: Aug 2008
Posts: 21,314
ON, Canada eh?
Check for poor connections at the alternator. (And or Battery, but if it was replaced most likely not here)

Meter the thick wire on the alternator to the battery ground and see if you have 14 volts at idle. Then try just the battery posts. If the voltage is higher at the back of the alternator referenced to ground than it is at the battery you have a bad connection.

You could also have a faulty voltage regulator in the alternator that functions normally when the alternator spins faster but fails to do it's job when it spins slower because internal resistances change. I have seen this before.

What's it like with every possible accessory running at idle / 2,000 rpm?


Last edited by StevieC; 12/04/17 08:40 PM.

'18 Dodge Grand Caravan GT - AMSOIL SS 5w20
'06 Santa Fe - 535,000km AMSOIL SS 0w30 / ATF
Re: Sonata strange battery charging behavior [Re: Nick1994] #4594440
12/04/17 08:49 PM
12/04/17 08:49 PM
Joined: Dec 2002
Posts: 42,301
New Jersey
JHZR2 Offline
JHZR2  Offline
Joined: Dec 2002
Posts: 42,301
New Jersey
Must be a "smart" alternator. BMW has done it for a few years, adding more charge under no throttle/braking, and less to reduce load under normal use. Some cars even have a gauge showing it.

My hybrid has a DC voltage of 12 and change under normal use, goes up to 14+ with headlights on, and IIRC other stuff. Never noticed a change in the fans though. Different controls/electronics though. The hybrid voltage is controlled by a power converter, as the 12V battery is charged via a dc-dc converter from the HV hybrid battery.

Re: Sonata strange battery charging behavior [Re: Nick1994] #4594443
12/04/17 08:50 PM
12/04/17 08:50 PM
Joined: Nov 2017
Posts: 382
North of you Idaho
KneeGrinder Offline
KneeGrinder  Offline
Joined: Nov 2017
Posts: 382
North of you Idaho
More than likely the alternator has a faulty voltage regulator, maybe it was smuggled across the boarder from the north...j/k


08 Tribeca 86k PUP 5w30 wix
06 Accord Hybrid 134k PPHM 0w20 wix
02 Chevy k3500 99k Delvac 1 esp 5w40 wix
00 F350 136k Delvac 1300 15w40 wix
Re: Sonata strange battery charging behavior [Re: KneeGrinder] #4594459
12/04/17 09:20 PM
12/04/17 09:20 PM
Joined: Nov 2010
Posts: 808
VA
Thax Offline
Thax  Offline
Joined: Nov 2010
Posts: 808
VA
Most likely have a faulty alternator. Charging voltage should be between 13v-14.5v depending on load ,rpm and ambient temps.


2000 Ford Explorer Limited 5.0L AWD
2018 KIA Soul EX 2.0L
ASE P2 Parts Specialist
AIA Import Part Specialist
KIA certified Senior Technician, Hybrid certified.
Re: Sonata strange battery charging behavior [Re: Nick1994] #4594464
12/04/17 09:30 PM
12/04/17 09:30 PM
Joined: Aug 2003
Posts: 13,146
NE,Ohio
Rand Offline
Rand  Offline
Joined: Aug 2003
Posts: 13,146
NE,Ohio
Its hyundai's smart alternator strategy.

Same thing on the 2010 accent only even more so on newer models.

They fully load the alternator in coasting.. and not so much at other times..

I think its asinine to save .2mpg but it is what it is.

nothing to see here operating as engineered and intended.


2019 Jeep Cherokee Trailhawk 2.0T
Re: Sonata strange battery charging behavior [Re: Nick1994] #4594483
12/04/17 09:57 PM
12/04/17 09:57 PM
Joined: Sep 2016
Posts: 167
MN
Tman220 Offline
Tman220  Offline
Joined: Sep 2016
Posts: 167
MN
This is a charging strategy that is used for extra mpg's. Lots of cars have this feature and the reason you don't hear of it is because it works much better than BMW's (too aggressive) approach which kills batteries.

There is nothing wrong with your car, alternator, or voltage regulator. My 2012 regal uses a similar strategy, as well as my (gasp!) 2004 Civic.

Sleep well it's normal.


2012 Regal GS Turbo PP 5w30
1994 Camaro Z28 LT1 355 CI, 430 RWHP PP 5W30
Re: Sonata strange battery charging behavior [Re: Rand] #4594484
12/04/17 10:00 PM
12/04/17 10:00 PM
Joined: Aug 2006
Posts: 9,887
Central Washington
Colt45ws Offline
Colt45ws  Offline
Joined: Aug 2006
Posts: 9,887
Central Washington
Originally Posted By: Rand
Its hyundai's smart alternator strategy.

Same thing on the 2010 accent only even more so on newer models.

They fully load the alternator in coasting.. and not so much at other times..

I think its asinine to save .2mpg but it is what it is.

nothing to see here operating as engineered and intended.

Agree.
This is the new norm. And I think thats why the long pro-rated battery warranties disappeared. But thats my pet conspiracy theory.


-Colton
2002 Ford Crown Vic PI 207k, Ex-Kootenai County, ID Unit #42
Down for engine swap
2003 Ford Crown Vic PI 75k
Castrol EDGE HM 5W30, Fram XG2
Re: Sonata strange battery charging behavior [Re: Nick1994] #4594503
12/04/17 10:30 PM
12/04/17 10:30 PM
Joined: Apr 2017
Posts: 1,455
San Rafael, CA
dogememe Offline
dogememe  Offline
Joined: Apr 2017
Posts: 1,455
San Rafael, CA
totally normal. "smart charging" has been common since the early 2000s in many vehicles. When you are accelerating it reduces alternator load... I think some newer cars disable AC compressor under heavy acceleration too?

Last edited by dogememe; 12/04/17 10:32 PM.

2010 Ford Escape 2.5 ~91K Miles: AMSOIL SS 5W-30, AMSOIL SS FE ATF.
1995 Chevy Silverado 5.7 ~277K Miles: Delo 10W-30, AMSOIL OE MV ATF.
AMSOIL
Re: Sonata strange battery charging behavior [Re: dogememe] #4594558
12/05/17 01:21 AM
12/05/17 01:21 AM
Joined: Jul 2008
Posts: 685
Maryland USA
rubberchicken Offline
rubberchicken  Offline
Joined: Jul 2008
Posts: 685
Maryland USA
I had a 1985 Camaro that would disable the a/c compressor under hard acceleration, so that in itself is not a new feature.

Re: Sonata strange battery charging behavior [Re: Nick1994] #4594582
12/05/17 02:50 AM
12/05/17 02:50 AM
Joined: Apr 2016
Posts: 782
Specific Ocean
Kibitoshin Offline
Kibitoshin  Offline
Joined: Apr 2016
Posts: 782
Specific Ocean
A lot of newer cars will also have a current sensing ring on one of the battery leads to measure current draw. The amount of amps leaving/entering the battery also determines the alternator duty cycle. On GM's turning on the headlights disables the smart charging mode.

Ammeter coil on negative cable that measures amp draw on a 2016 GMC Sierra.


Someone will diag this as a bad alternator when misinterpreting this data:

Last edited by Kibitoshin; 12/05/17 02:51 AM.

Shin Gekiretsu Shin'ou'hou
01 Toyota Tundra 2WD V8 4.7L
02 Chevy Silverado C1500 V8 5.3L
Re: Sonata strange battery charging behavior [Re: Nick1994] #4594688
12/05/17 07:31 AM
12/05/17 07:31 AM
Joined: Aug 2008
Posts: 21,314
ON, Canada eh?
StevieC Offline
StevieC  Offline
Joined: Aug 2008
Posts: 21,314
ON, Canada eh?
My Dodge Journey has a clutch on the pulley but the voltage regulator keeps the voltage the same regardless of acceleration, deceleration and idling. That's really weird if that is what it is. Haven't seen that before. (Smart Alternator Charging)


Last edited by StevieC; 12/05/17 07:32 AM.

'18 Dodge Grand Caravan GT - AMSOIL SS 5w20
'06 Santa Fe - 535,000km AMSOIL SS 0w30 / ATF
Re: Sonata strange battery charging behavior [Re: Rand] #4594809
12/05/17 09:46 AM
12/05/17 09:46 AM
Joined: Aug 2003
Posts: 11,014
Buffalo, NY
JTK Offline
JTK  Offline
Joined: Aug 2003
Posts: 11,014
Buffalo, NY
Like Rand said above, it's the technology built into the charging system by Hyundai to maximize fuel economy causing this. Pretty rare to have an alternator or charging system issue with a 2015.


2017 Ram 1500 4x4, 3.6L. 2016 Nissan Quest SV (Babe magnet IV)
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