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ISG and Battery Levels

17K views 71 replies 27 participants last post by  FishRamLion 
#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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#2 ·
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.
 
#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.
 
#7 ·
That will explain why my ISG is not working. I took my 2020 Santa Fe SEL to the dealer and they replaced my battery, but that was after telling me that a jump start on these AGM batteries will damage about 10% of the cells. I called Interstate Batteries and they confirmed what the dealer told me. So after dealer on Jan 6th put in a new battery with a full charge my ISG Stop/Start worked great for a couple of days. But I normally drive less than 10 miles per trip and only a couple of times per day. So Jan 6th new battery, then on Jan 15th, after ISG not working for almost a week, I put a battery charger on my battery and it reflected it was at 25% charge. (I forgot to measure voltage at that time). After 5hrs and supposedly it was at a full charge I disconnected the charger and turned on the headlights and measured 12.43v. With Headlights off I get 12.67v. So maybe I didn't let the charger charge long enough. Anyways the dealer also stated that once a week I should drive the car for 1 hour to charge up the battery. I'll put the charger on all night and see if that helps. Other then this I Love my Santa Fe. My charger is a Noco Genius 10. Noco verified that it will work on a 2020 Santa Fe.
 
#11 ·
That will explain why my ISG is not working. I took my 2020 Santa Fe SEL to the dealer and they replaced my battery, but that was after telling me that a jump start on these AGM batteries will damage about 10% of the cells. I called Interstate Batteries and they confirmed what the dealer told me. So after dealer on Jan 6th put in a new battery with a full charge my ISG Stop/Start worked great for a couple of days. But I normally drive less than 10 miles per trip and only a couple of times per day. So Jan 6th new battery, then on Jan 15th, after ISG not working for almost a week, I put a battery charger on my battery and it reflected it was at 25% charge. (I forgot to measure the voltage at that time). After 5hrs and supposedly it was at a full charge I disconnected the charger and turned on the headlights and measured 12.43v. With Headlights off, I get 12.67v. So maybe I didn't let the charger charge long enough. Anyways the dealer also stated that once a week I should drive the car for 1 hour to charge up the battery. I'll put the charger on all night and see if that helps. Other then this I Love my Santa Fe. My charger is a Noco Genius 10. Noco verified that it will work on a 2020 Santa Fe.
After putting a full charge on my battery overnight my ISG worked perfectly the next day.
 
#8 ·
While I realize this isn’t addressing your question, is having the ISG not work really a bad thing?

While Hyundai’s implementation of it is pretty good, I still have concerns about the effect the system has on long-durability of parts like the starter motor (premature failure).

I will typically turn the system off when I get in the car, but I don’t experience a lot of stop-and-go traffic either.
 
#16 ·
I purchased my 2019 Santa Fe SE in July and the ISG worked fine for months, but quit working in late fall 2019. I am retired so many of my trips are short. That combined with the colder weather obviously impacted the battery's state of charge (SOC). After reading this (and other) threads, I charged the battery a few nights ago and the ISG has worked fine since. I don't generally use the ISG feature, but when it quit working I was concerned about which of the many ISG "rules of engagement" had failed...i.e. was there a serious issue. Thanks to the forum, I am relieved to find the problem, but still question Hyundai's ISG implementation in regards to battery management.

FYI...charger used: Harbor Freight "Viking 4 amp Automatic Microprocessor Controlled Battery Charger/Maintainer". Works great.
 
#17 ·
Hi also have a 2019 Santa Fe, my ISG system was working fine when I picked it up in April, since the winter started it has stopped working, and as I drive a fair distance, the engine has plenty of time to warm up, so I too am at a loss as to why it suddenly stopped working. I checked and my battery is charged.
 
#18 ·
Depends where you live, what accessories you have running, the temperature outside. Did you ever do a jumpstart on this battery? Why, because a jumpstart on an AGM battery will damage about 10% of the cells in the battery. My ISG stopped working after I had a jumpstart and the dealer even put a full charge on the battery for me afterward and that did not help. The dealer ended up putting in a new battery and that fixed my ISG. Been working perfectly the rest of the winter in WI.
 
#25 ·
I'm no expert, but I recall hearing an AGM battery should not be FAST CHARGED. I don't recall why, but a jump start is more like a quick charge... and if you have a low battery, charge it on the 2A or max 10A. Of course, if you are stuck somewhere or in the right (wrong) situation, a jump start might be worth it.... just my thoughts...
 
#26 ·
That would be correct. AGM batteries are designed to be charged with low current and jump starting causes large current to pass through the battery. Better method would be to charge vehicle AGM battery of another AGM battery long enough to be able to start vehicle. Also alternators are designed to maintain AGM battery levels not charged it. That's why when voltage on AGM battery drops below certain level [usually around 10V] it can only be charged using dedicated AGM battery charger.
Edit:
No idea where 10% comes from though - sounds to me like a myth.
 
#31 ·
I don't see why that would be an issue. I've kept both "stands" batteries as well as AMG batteries on a battery tender for extended periods due to winter weather here in Iowa. I've owned street rods and Corvettes that sit for months on end due to being "nice weather" cars. Many folks in my Corvette Club and Street Rod Club do exactly the same to maintain batteries during those long Iowa Winter months
 
#35 ·
I've been commenting that my ISG hasn't worked since Oct 19, quit after doing the 953 update for some strange reason. Yesterday I accidentally ran the battery down in my 2nd car with the trunk ajar. I thought that wasn't supposed to happen but I put our digital charger on and battery showed 50%, so I charged it. Since I had the charger out I thought let me just check the Santa Fe, which had been driven 500+ miles in the past week mostly daytime drives ... and it showed 53% on this 18 mon old battery?! This is a good quality Schumacher digital charger with trickle AGM mode and it took an hour for it to show 84%. Then in a few minutes it jumped to 100% shutting off the charger. Strange.
Anyway I plan to do some drives of this Santa Fe tomorrow and will see if this fully charged battery will allow the ISG to kick in after full warmup. Will report back in a few days.
 
#39 ·
You may have figured this out, but the battery monitor can take a 3 or 4 starts (after charging is complete and the battery has sat for 4 hours) to allow ISG activation according to the manual. This means the ISG may not engage until the time and the starts have taken place. I drive my SF daily but most trips are short so I also charge the battery on occasion (when I don't get out on the highway and rack up some miles) and it usually takes 3 starts after charging for the IGS to start working again. Generally when I connect the charger I'm reading middle 60's and I can tell it's time for charging by the behavior of the ISG.
 
#36 ·
Perhaps mystery solved or at least one variable of this many "variabled" ISG equation.
I drove the Santa Fe around town yesterday on a 46 F day, probably 6 of my initiated start/stops over 30-40 miles. It had plenty of time to warm up, heater fan was NOT on much at all (in fact in Auto mode it switched to AC once since full sun had warmed up the interior quite a bit on a 46 deg day, so off goes Auto, not needing AC in winter). As for many months now, no ISG at stoplights etc.

I thought I should do a quick battery check this morning, popped the hood and battery measures 11.9v. I put my trickle AGM charger on again (see post 35) and again my battery is at 53% ?!?! It's around 40 F in the garage, no lights on so I either have:
  • Some weird parasitic discharge going on. But I doubt it, car always starts fine all winter even a few times when below zero.
  • The battery is going bad. Possible. I might swing by a local BatteriesPlus that checks it for free. No plans to swing by the dealer until at least late April for an oil change.

I will put out an update when I find the source. But it's possible the ISG did not quit last Nov due to this 953 software update and I just have a bad or weak charge battery which should be covered under warranty 3 years the way I read the warranty guide.
 
#37 ·
Perhaps mystery solved or at least one variable of this many "variabled" ISG equation.
I drove the Santa Fe around town yesterday on a 46 F day, probably 6 of my initiated start/stops over 30-40 miles. It had plenty of time to warm up, heater fan was NOT on much at all (in fact in Auto mode it switched to AC once since full sun had warmed up the interior quite a bit on a 46 deg day, so off goes Auto, not needing AC in winter). As for many months now, no ISG at stoplights etc.

I thought I should do a quick battery check this morning, popped the hood and battery measures 11.9v. I put my trickle AGM charger on again (see post 35) and again my battery is at 53% ?!?! It's around 40 F in the garage, no lights on so I either have:
  • Some weird parasitic discharge going on. But I doubt it, car always starts fine all winter even a few times when below zero.
  • The battery is going bad. Possible. I might swing by a local BatteriesPlus that checks it for free. No plans to swing by the dealer until at least late April for an oil change.
I will put out an update when I find the source. But it's possible the ISG did not quit last Nov due to this 953 software update and I just have a bad or weak charge battery which should be covered under warranty 3 years the way I read the warranty guide.
I’m in the same boat as you and, likely, many others. My ISG hasn’t worked for months. Several months ago the dealer said it was due to a low battery charge. They told me...get this...that I wasn’t driving the vehicle enough. Sure, most of my daily trips are short, but not exceptionally so.

Anywho, they charged the battery, but the ISG only worked for a week or two. It’s been dead ever since. Some would say that this is a blessing since they hate ISG. I’m starting to agree, although I think the ISG worked pretty smoothly (when it worked). Come on Hyundai, get on the stick! If you’re going to put a feature in the vehicle, make it work.
 
#38 ·
My ISG had not worked once in the 1,500 miles I've driven my 2020 Santa Fe 2.0t Limited. That is, until I took it in for an early 1st oil change and the dealer CHARGED the battery. Guess what? Now it works so I'm "wearing out" the ISG button!!!!!
 
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