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Discussion Starter #1
Hello all,
My wife has a 2010 Hyundai Santa Fe with a 3.5 Lambda V6 engine which has an intermittent battery charging system failure and I am hoping to gain some insight into the cause of failure.
First off, I am an electrical engineer so I know my way around a DMM/Oscilloscope/etc.
The alternator, battery, and battery current sensor (it has the so-called "smart" battery management system) have all been replaced but there has been no change (the problem stays the same).
What happens is that, if I disconnect the battery (which restores the default values in the ECM) and wait 10 minutes and then reconnect the battery the changing system will work for 2 days up to 1 week with no issues (the battery charging voltage is right around 14.4VDC) however, during the period that the alternator/charging system is working, I do not see any signs that the smart battery management system is active (the battery voltage always stays right around 14.4VDC and never drops to around 12.6V like it is supposed to when accelerating).
As I previously mention, when the charging system fails, the only way to restore it is to disconnect the battery and then reconnect it after 10 minutes or so (I think this may be a big clue to what is going on).
Also, when the battery charging system fails, the "ALTERNATOR/BATTERY DISCHARGE" LED does NOT turn on like it is supposed to (although it does turn on when the key is in the "ON" position).
It is as if the ECM is gating bad data possibly from the battery current sensor which it interprets as the battery is fully charged (or overcharged) so it shuts down alternator.
This weekend I will try removing the two big connectors from the ECM (located in the engine compartment) and try spray cleaning the pins and sockets and see what happens (I think that having the ECM in the engine compartment may be problematic as it is a harsher environment than if it were located in the interior of the vehicle.
So that is all I know to say about my situation at the moment.
Any comments or advice would be greatly appreciated.
Thanks for reading this!
P.S. I have checked all of the charging system fuses and various ground straps and they are all good.
P.S.S. There are no DTC's.
Jeff from Cuyahoga Falls, OH
 

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What about parasitic draw?
 

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Discussion Starter #3
Hello all,
My wife has a 2010 Hyundai Santa Fe with a 3.5 Lambda V6 engine which has an intermittent battery charging system failure and I am hoping to gain some insight into the cause of failure.
First off, I am an electrical engineer so I know my way around a DMM/Oscilloscope/etc.
The alternator, battery, and battery current sensor (it has the so-called "smart" battery management system) have all been replaced but there has been no change (the problem stays the same).
What happens is that, if I disconnect the battery (which restores the default values in the ECM) and wait 10 minutes and then reconnect the battery the changing system will work for 2 days up to 1 week with no issues (the battery charging voltage is right around 14.4VDC) however, during the period that the alternator/charging system is working, I do not see any signs that the smart battery management system is active (the battery voltage always stays right around 14.4VDC and never drops to around 12.6V like it is supposed to when accelerating).
As I previously mention, when the charging system fails, the only way to restore it is to disconnect the battery and then reconnect it after 10 minutes or so (I think this may be a big clue to what is going on).
Also, when the battery charging system fails, the "ALTERNATOR/BATTERY DISCHARGE" LED does NOT turn on like it is supposed to (although it does turn on when the key is in the "ON" position).
It is as if the ECM is gating bad data possibly from the battery current sensor which it interprets as the battery is fully charged (or overcharged) so it shuts down alternator.
This weekend I will try removing the two big connectors from the ECM (located in the engine compartment) and try spray cleaning the pins and sockets and see what happens (I think that having the ECM in the engine compartment may be problematic as it is a harsher environment than if it were located in the interior of the vehicle.
So that is all I know to say about my situation at the moment.
Any comments or advice would be greatly appreciated.
Thanks for reading this!
P.S. I have checked all of the charging system fuses and various ground straps and they are all good.
P.S.S. There are no DTC's.
Jeff from Cuyahoga Falls, OH
What about parasitic draw?
I forgot to mention anything in my first post about parasitic draw and that is something that I have not yet checked but I will do so this weekend. According to a Hyundai service document that I found at Mitchell's, it needs to be less than 50mA DC. Thanks for suggesting that and I will definitely check that out as I know that it can confuse the ECM.
 

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First off, I am an electrical engineer so I know my way around a DMM/Oscilloscope/etc.
The alternator, battery, and battery current sensor have all been replaced
An electrical engineer that likes a good game of parts darts :)

I didn't see any mention of the failure in your post. You tell us it works when you disconnect the battery, but you didn't tell us what the failure was that caused you to disconnect the battery in the first place??
 

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You mentioned that you're expecting the voltage output to drop to around 12.6v while accelerating, I have never seen that on my '13 Sonata nor on 14 SFS. My ranges are around 13.8 - 14.3v. Have you done a voltage drop between alternator and battery?

Based on both my vehicles not dropping charging voltage, what you're describing doesn't sound incorrect. When you say your 'charging system fails', are you getting the battery icon while driving, your battery is not charging... etc.? how are you determining that your charging system is failing?

What is the duty cycle you're seeing from the smart charging system? More powerful scantools should show what the ECM is commanding and you can measure it yourself to make sure the command is getting to the alternator.
 

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Discussion Starter #6 (Edited)
When I say that the charging system fails I mean that there is no charging voltage/current from the alternator and the battery continues to discharge (and the voltage continues to drop) while you are driving until you get down to around 8 volts then the SUV goes into limp mode and then it dies. Also - on the way down to 8 volts the ABS yellow Icon turns on and then other yellow Icons turn on BUT the Battery Discharge red warning Icon never turns on (except when the ignition key is in the "ON" position so I do know that the LED is good). I do not remember exactly where I read that the alternator shuts down during acceleration but maybe that is incorrect although I have read many Hyundai forum posts where people were concerned that there was a charging system problem because the voltage would alternate between around 12.6 and 14.4 V but then they learned that is normal for a Hyundai smart charging system. I have been under the impression that a Hyundai smart battery management system completely shuts the alternator off under certain conditions. As far as duty cycle is concerned I have yet to look at that but I will do so this weekend (using an oscilloscope). I wish I had access to a more sophisticated scan tool but, at the moment, I do not. I did take the vehicle to a Hyundai dealer and they said that BEFORE they would run any diagnostics they would have to install a new Hyundai alternator to the tune of about $700.00 (they gave me no other options). If I could find someone who would be willing to just run diagnostic WITHOUT going ahead and indiscriminately installing new parts, I would gladly take the vehicle to them. I did do a voltage drop measurement between the "B" stud on the alternator and the (+) battery post and it is minimal (I forget what it was but I will re-measure it and then post the value). I also measured the voltage drop between the case of the alternator and the (-) battery terminal and it was also minimal. I think that it is very possible that different auto manufacturers have different "Smart" battery management schemes and maybe some do not command the alternator to shut completely down. It would be nice if the alternator was a little more accessible than it is. I will post some "more better" measured values this weekend. I want to thank everybody for their input. Oh, one other thing, I have checked that the alternator is spinning properly when the charging system is in the "failed" mode and it is good. Also -> I have never heard the phrase "parts darts" before but I think that is very descriptive of the situation.
 

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When I say that the charging system fails I mean that there is no charging voltage/current from the alternator and the battery continues to discharge (and the voltage continues to drop) while you are driving until you get down to around 8 volts then the SUV goes into limp mode and then it dies. Also - on the way down to 8 volts the ABS yellow Icon turns on and then other yellow Icons turn on BUT the Battery Discharge red warning Icon never turns on (except when the ignition key is in the "ON" position so I do know that the LED is good). I do not remember exactly where I read that the alternator shuts down during acceleration but maybe that is incorrect although I have read many Hyundai forum posts where people were concerned that there was a charging system problem because the voltage would alternate between around 12.6 and 14.4 V but then they learned that is normal for a Hyundai smart charging system. I have been under the impression that a Hyundai smart battery management system completely shuts the alternator off under certain conditions. As far as duty cycle is concerned I have yet to look at that but I will do so this weekend (using an oscilloscope). I wish I had access to a more sophisticated scan tool but, at the moment, I do not. I did take the vehicle to a Hyundai dealer and they said that BEFORE they would run any diagnostics they would have to install a new Hyundai alternator to the tune of about $700.00 (they gave me no other options). If I could find someone who would be willing to just run diagnostic WITHOUT going ahead and indiscriminately installing new parts, I would gladly take the vehicle to them. I did do a voltage drop measurement between the "B" stud on the alternator and the (+) battery post and it is minimal (I forget what it was but I will re-measure it and then post the value). I also measured the voltage drop between the case of the alternator and the (-) battery terminal and it was also minimal. I think that it is very possible that different auto manufacturers have different "Smart" battery management schemes and maybe some do not command the alternator to shut completely down. It would be nice if the alternator was a little more accessible than it is. I will post some "more better" measured values this weekend. I want to thank everybody for their input. Oh, one other thing, I have checked that the alternator is spinning properly when the charging system is in the "failed" mode and it is good. Also -> I have never heard the phrase "parts darts" before but I think that is very descriptive of the situation.
Being an intermittent problem, I'd buy one of those cigarette lighter voltmeter(with a digital readout)that you stick in the cigarette lighter hole. Then you can constantly monitor what your alternator is putting out as you are driving.
 

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I did take the vehicle to a Hyundai dealer and they said that BEFORE they would run any diagnostics they would have to install a new Hyundai alternator to the tune of about $700.00 (they gave me no other options).
WHAT? And you agreed to that? Are you nuts?

morbius123 said:
If I could find someone who would be willing to just run diagnostic WITHOUT going ahead and indiscriminately installing new parts, I would gladly take the vehicle to them.
How hard did you look? I'm pretty sure any decent, reputable independent garage (and most Hyundai dealers too, I'm sure) would test the charging system without expecting you to replace parts first. Why would they want to replace something before doing the diagnosis? And why would anyone (especially an electrical engineer) agree to that?
 

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Did the OP mention whether he has the electrical schematics of the charging system??
Smart charging systems usually have a load detector
Is it possible the load detector is faulty and turning off the alternator???
Is the wiring to the load detector frayed or shorting out??
 

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Is it possible the load detector is faulty and turning off the alternator???
Unlikely, given that he already replaced it.

avisitor said:
Is the wiring to the load detector frayed or shorting out??
I'm sure an electrical engineer would have noticed if it was when he replaced the detector/battery current sensor.
 

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Discussion Starter #11
A couple of comments:
1) I did purchase a cigarette lighter digital voltmeter some time ago which is, of course, very useful given my particular problem.
2) When I took the vehicle to the Hyundai dealer I did NOT have them install a new alternator (as a matter of fact, they recommended that I do it myself to save money).
3) The wiring to the "load detector" (battery current sensor) looks good but I will double check that this weekend. Also it is my understanding that the EMC is supposed to throw a code if it detects an open circuit or short with the battery current sensor and there is no code (at least not that I can find). I did previously take the vehicle to a "professional" independent auto repair shop and they said there were no DTC codes in the ECM and I assume that their OBD2 scanner was more sophisticated than mine which is just a simple one. At the time I took the vehicle to this shop the battery charging problem did not "show itself" (naturally) even though they had it for two days and allegedly did extensive testing on the charging system (so they said) but who knows how much testing they really did. They said that they could not find anything wrong with the charging system and charged me $120.00.
4) There are other shops in the area that I could try if I run into a brick wall on this but I would like to resolve the problem myself if possible.
5) Yes I have an accurate wiring diagram of the charging system which I got from Mitchell's. Perhaps I will post it here if that is allowable.
6) Yesterday I happen to notice that one of the machine screws that secures the ECM to the body of the vehicle (in the engine compartment) is barely threaded in which indicates to me that at some time somebody was messing with the ECM as I doubt that it would have been like this new. I will check the electrical grounding to the case of the ECM and make sure that it is good. BTW: I bought this vehicle used about 6 months ago.
7) Thanks!
 

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Discussion Starter #13 (Edited)
So I did a few electrical tests this morning and here is what I got (measured with my Fluke 189 DMM):
voltage drop from (-) battery post to the case of the alternator: 21.42 mV DC
voltage drop from (+) battery post to the "B" stud on the alternator: 77.32mV DC
Parasitic current draw: 20mA DVC
I also checked for continuity between the metal case of the ECM and the (-) battery post and I found it to be have a VERY intermittent and poor ground (as I mentioned before there is one mounting machine screw that is barely threaded in and the ECM is somewhat sloppy and loose in it's mounting to the car body). Before I post anything else I will tighten this screw down and recheck the ground and see if the charging system fails again which could take anywhere from a few hours to a few weeks.
Jeff
 

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Discussion Starter #14
I just took my wife's van for a little test drive and so far, so good (my cigarette lighter digital meter displayed 14.1 to 14.5V. At this time I am not going to worry or try to figure out the fine details of the smart battery management system (how the voltage varies under different conditions) I just want the system to, overall, provide sufficient electrical power to keep the vehicle running and keep the battery charged (I guess what I am saying is that I am not going to be concerned if I don't see significant changes of maybe 1 to 2 volts while I am driving the vehicle). Now only time will tell if it is truly fixed.
 

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Unlikely, given that he already replaced it.
I must have missed where he said that he replaced the load detector??

I'm sure an electrical engineer would have noticed if it was when he replaced the detector/battery current sensor.
Not everyone is as good as you in being so observant.
Also, everyone makes mistakes once in a while.
That is just being human.

A note: Hyundai's are infamous for faulty grounds.
And corrosion doesn't help.
 

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Discussion Starter #18
It's been about 1 week now since I repaired the open ground to the ECM and all is good.
What we are seeing is that the battery voltage drops down to about 12.6 (the alternator turns off) when the vehicle is stopped and idling but the charging voltage always picks back up as soon as you accelerate (according to other posts in this forum this is normal). We are also no longer seeing other unrelated intermittent DTC codes that we were seeing before I repaired the ground. My wife is very happy now. Thanks! Jeff
 
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