Sonata strange battery charging behavior

[Nick1994]

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.

 

[eljefino]

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.

 

[KneeGrinder]

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.

 

[StevieC]

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?

 

[JHZR2]

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.

 

[KneeGrinder]

More than likely the alternator has a faulty voltage regulator, maybe it was smuggled across the boarder from the north...j/k

 

[Thax]

Most likely have a faulty alternator. Charging voltage should be between 13v-14.5v depending on load ,rpm and ambient temps.

 

[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.

 

[Tman220]

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.

 

[Colt45ws]

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.

 

[dogememe]

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?

 

[rubberchicken]

I had a 1985 Camaro that would disable the a/c compressor under hard acceleration, so that in itself is not a new feature.

 

[Tomioka]

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:

 

[StevieC]

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)

 

[JTK]

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.

 

[SatinSilver]

Originally Posted By: Nick1994

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!

The $48 Value one from Walmart?

 

[Nick1994]

Originally Posted By: SatinSilver

Originally Posted By: Nick1994

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!

The $48 Value one from Walmart?

Unfortunately they don't make one in my car's size. A buddy of mine is a mechanic and I use his account to buy parts at his cost, so I got the new one through his wholesaler.

 

[Jeffs2006EvoIX]

Originally Posted By: JHZR2

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.

I believe This is correct. Hyundai does use "Smart" alternator technology. I found that out in my 2011 Elantra. Had a similar issue like the OP. Jeff

 

[Vuflanovsky]

According to one of Hyundai's marketing blurbs for the current Accent (2012- ), the smart alternator system provides the second largest MPG gain behind the addition of direct injection versus the last generation car. I'm sure it's application-specific but I'd guess it might be considerably more than .2 MPG, as mentioned earlier, if that's the case.

 

[NHGUY]

I laugh,Chrysler has had computer controlled charging since 1985 on EFI models,now everybody is a Johnny Come Lately when it comes to catching up.