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Discussion Starter #1
I have a 2019 Santa Fe Ultimate 2.4L FWD, bought it back in April. ISG has been acting normal up until about 3 weeks ago, where it hasn't activated (turning off the engine) once in that period.

I know there is a long list of criteria, I pulled DTC codes (none) and then checked battery voltage and saw 12.3V yesterday. Didn't disconnect battery fully, but I assume parasitic loads are very small. Since it's an AGM battery, 12.3V puts it at SOC 50% or so-- which seems like a likely culprit fro ISG not kicking on, since if I remember correctly the activation criteria is > 68%. Next question is why is the battery level at 50% even after driving an hour on the highway.

I took it to the dealer as a walk-in, and they tested the battery-- CCA's were fine though charge level was 50%. It passed as Good, so there wasn't much more they could do without holding the car for a few days for a diagnosis.

I checked the battery after driving another hour or so today, 12.3V as well. When idling after a cold start, voltage observed at the terminal was around 14.5V, so it seems like the alternator is working fine as well. Some more searching online, and I ran into a post on talkhyundai.com that the alternator management system (AMS) controlled by the ECU will avoid charging the battery unless it really needs to to save mpg, except opportunistically when decelerating. Thus, the post said, it's possible that if driving habits are shorter trips, the AMS will allow the battery to settle at a lower charge level, below the threshold for ISG to activate.

I did change my driving habits ~2 months ago from regularly driving on the freeway to only driving on the freeway a couple times a week (girlfriend moved in, she previously lived about 45 minutes away), though I'd still estimate ~20+ miles of a driving most days, but more 30-45 mph and stop lights. So, it seems possible that not getting as much regular charge on the battery if the alternator is selecting not to kick in on these types of trips.

My question is: Has anyone else run into ISG not activating for weeks due to lower battery charges, or has anyone observed continual 50% or so battery charge levels?
 

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I have a 2019 Santa Fe Ultimate 2.4L FWD, bought it back in April. ISG has been acting normal up until about 3 weeks ago, where it hasn't activated (turning off the engine) once in that period.

I know there is a long list of criteria, I pulled DTC codes (none) and then checked battery voltage and saw 12.3V yesterday. Didn't disconnect battery fully, but I assume parasitic loads are very small. Since it's an AGM battery, 12.3V puts it at SOC 50% or so-- which seems like a likely culprit fro ISG not kicking on, since if I remember correctly the activation criteria is > 68%. Next question is why is the battery level at 50% even after driving an hour on the highway.

I took it to the dealer as a walk-in, and they tested the battery-- CCA's were fine though charge level was 50%. It passed as Good, so there wasn't much more they could do without holding the car for a few days for a diagnosis.

I checked the battery after driving another hour or so today, 12.3V as well. When idling after a cold start, voltage observed at the terminal was around 14.5V, so it seems like the alternator is working fine as well. Some more searching online, and I ran into a post on talkhyundai.com that the alternator management system (AMS) controlled by the ECU will avoid charging the battery unless it really needs to to save mpg, except opportunistically when decelerating. Thus, the post said, it's possible that if driving habits are shorter trips, the AMS will allow the battery to settle at a lower charge level, below the threshold for ISG to activate.

I did change my driving habits ~2 months ago from regularly driving on the freeway to only driving on the freeway a couple times a week (girlfriend moved in, she previously lived about 45 minutes away), though I'd still estimate ~20+ miles of a driving most days, but more 30-45 mph and stop lights. So, it seems possible that not getting as much regular charge on the battery if the alternator is selecting not to kick in on these types of trips.

My question is: Has anyone else run into ISG not activating for weeks due to lower battery charges, or has anyone observed continual 50% or so battery charge levels?
I’m totally with you, Kiddo. My ISG has not activated for weeks either. I suspect a low battery charge level.
 

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Mine has not activated for a few months. Some on these forums would like that it does not activate and I am on the fence so I have not taken it in.
 

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Discussion Starter #4
Battery was measuring at 12.3V, then 12.4V, and then this morning 12.15V, 12.15V again this evening (only drove around town a bit). Really not sure why battery voltage seems to be tanking... no issues starting the car yet, however.
 

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Battery was measuring at 12.3V, then 12.4V, and then this morning 12.15V, 12.15V again this evening (only drove around town a bit). Really not sure why battery voltage seems to be tanking... no issues starting the car yet, however.
You may have answered your own question.
 

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Discussion Starter #6
You may have answered your own question.
This wasn't a full day of town driving, just like about 25 minutes or so for the full day.

Measured battery level again this morning and about 12.05V now. Haven't tried turning it on yet.
 
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