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2019 Ioniq Blue HEV Plugin
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Hi,
I woke up this morning to a dead car. Doors won’t open with fob. Nothing worked. I had the car charged 1/2 way so thought strange for battery to die suddenly. I was finally able to get key cover off to open car the cover was frozen on. I got a boost and car started up right away. I went to check the battery level and still 1/2 charged when I realized that there must be 2 separate batteries. One for starting and one for driving. Did some research online here and seems people have this issue. However this is where it gets interesting! I frequently start my car from my phone and the past 2 days I was getting an error on my phone that couldn’t start remotely because the car hasn’t been started in a few days. Now I’ve been driving it every day starting and stopping it few times a day. At first I thought it’s a glitch in the app. However now I’m convinced that it’s related to a battery issue. Perhaps the EV battery is not charging the small battery. I did not get any warning messages And no lights were left on in the car. Any thoughts to this? I’m in the US. Also anyway to check the status of the small battery besides hooking up a booster which o don’t have.? Thanks
 

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The high voltage battery drives the car, cranks the gas engine, and runs the air conditioning. Everything else (computers, dashboard, infotainment, lights, fans, seat heaters, outlets) runs off the 12V system. In US HEV models there's a 12V lithium ion battery integrated into the high voltage pack that keeps Bluelink and the security system going when the car is off, which is also used to boot the thing back up when you 'start' the car. Once the car is 'running' a DC-DC converter runs the 12V system from the high voltage battery, which also charges the 12V battery back up.

If the 12V battery gets too low while the car is parked, a relay opens to disconnect it and preserve the remaining charge which basically kills the car. Once you've let yourself back into the car manually however, you can push the 12V Reset button on the dash to temporarily reconnect the 12V battery to the system. Immediately 'start' the car after that, and give it at least 30 minutes of run time to get the 12V battery back to an adequate level. (I don't know how long it needs to fully recharge, but probably more than that.) The car doesn't actually need to drive anywhere for those 30 minutes, it just needs to be on and ready to drive (i.e. the little green car with the double ended arrow underneath it on the dash needs to be lit).

You're lucky, the BEV and PHEV models (and even the HEV model in some countries) have old fashioned lead-acid 12V batteries, with no safety disconnect and 12V Reset button. When their 12V goes dead there's no choice but to either get a boost or disconnect it for charging...
 
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Nice reply as usual Kevin, but OP has PHEV, not HEV.

To the OP, you have a small 12 volt lead acid battery inside behind a door right rear of your car. The intermittent charging of such batteries by numerous PHEV/BEVs brands leads to dead batteries and early battery failure. Your situation fits this scenario. Why the engineers designed systems like this is unknown, but you can make the battery less likely to fail and have an ordinary lifespan with regular maintenance per many forum posts on many makes and models of PHEV/BEVs. That is to run a smart trickle charger overnight (or longer) at least once a month. Affected owners often also get a portable jump charger as insurance so they won't get stranded again on a trip.

Of course, you should investigate possible issues of excessive drain which can cause dead batteries in any kind of car. In my case, I was twice burned by two different models of OBD readers left plugged in overnight. I don't leave one plugged in anymore.

Problems posted on forums doesn't mean this issue happens to all owners, but I suspect most owners will end up replacing that rather expensive small battery within two years without use of a smart trickle charger - for ICE cars with always charging alternators, batteries usually last 3 to 5 years.
 

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D'oh! I spotted HEV in his signature but not the word Plug-in ahead of it, I just assumed that he'd posted in the wrong sub...
 
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I have been reading what seems like an awful lot of posts lately about dead 12v batteries in the Ioniq phev. It makes my head spin to try to make sense of all the posts. It feels like a real design fault, like something that I need to be prepared for someday. Something that worries me.

Well today I was walking thru a parking lot when a man said his battery was dead and asked if I could give his car a jump start. It's funny what goes thru your head in the 5 seconds before you must provide a response. It's cold out here... He's here for a doctors appointment, is he healthy... He's not wearing a mask... Do I want to do this... You know, some doubts for 5 seconds before I said 'Sure, I'll help'.

So it was actually an easy thing to do, we got his car started in just a few minutes. We talked for a while about cars. He used to be a car salesman and really seemed to admire the Ioniq. Besides the natural good feeling you get from helping someone, it was also a little reassuring. If it had been me in his shoes with a dead battery, you know it wasnt that bad.

This is actually the second time I have had to give someone a jump start since I've had my Ioniq. So for the moment I have the better score. I hope it stays that way.
 

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D'oh! I spotted HEV in his signature but not the word Plug-in ahead of it, I just assumed that he'd posted in the wrong sub...
That's odd! I didn't see the words Plug-in either.
Nice reply as usual Kevin, but OP has PHEV, not HEV.

To the OP, you have a small 12 volt lead acid battery inside behind a door right rear of your car. The intermittent charging of such batteries by numerous PHEV/BEVs brands leads to dead batteries and early battery failure. Your situation fits this scenario. Why the engineers designed systems like this is unknown, but you can make the battery less likely to fail and have an ordinary lifespan with regular maintenance per many forum posts on many makes and models of PHEV/BEVs. That is to run a smart trickle charger overnight (or longer) at least once a month. Affected owners often also get a portable jump charger as insurance so they won't get stranded again on a trip.

Of course, you should investigate possible issues of excessive drain which can cause dead batteries in any kind of car. In my case, I was twice burned by two different models of OBD readers left plugged in overnight. I don't leave one plugged in anymore.

Problems posted on forums doesn't mean this issue happens to all owners, but I suspect most owners will end up replacing that rather expensive small battery within two years without use of a smart trickle charger - for ICE cars with always charging alternators, batteries usually last 3 to 5 years.
"I was twice burned by two different models of OBD readers left plugged in overnight."
I had the dead lead-acid issue within the first year. The dealership paid for the tow back to their shop. They did not seem to know why it went dead so they just replaced the battery.
I have a device also that is plugged into the OBD that reports back to my insurance company concerning driving events and precisely where the car is parked over night. Unplugging it would void my eligibility to claim a percentage discount on my next years premium.
If you are accurate about the two year life span I'm about due for a failure!
🐧
 

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I have been reading what seems like an awful lot of posts lately about dead 12v batteries in the Ioniq phev. It makes my head spin to try to make sense of all the posts. It feels like a real design fault, like something that I need to be prepared for someday. Something that worries me.

Well today I was walking thru a parking lot when a man said his battery was dead and asked if I could give his car a jump start. It's funny what goes thru your head in the 5 seconds before you must provide a response. It's cold out here... He's here for a doctors appointment, is he healthy... He's not wearing a mask... Do I want to do this... You know, some doubts for 5 seconds before I said 'Sure, I'll help'.

So it was actually an easy thing to do, we got his car started in just a few minutes. We talked for a while about cars. He used to be a car salesman and really seemed to admire the Ioniq. Besides the natural good feeling you get from helping someone, it was also a little reassuring. If it had been me in his shoes with a dead battery, you know it wasn't that bad.

This is actually the second time I have had to give someone a jump start since I've had my Ioniq. So for the moment I have the better score. I hope it stays that way.
I viewed a Scotty Kilmer video recently where he describes the correct sequence of connecting the two vehicles. He stressed that there is a possibility of frying the electronics on the good car if one isn't careful about this.
For this reason only, I think I would have to say, 'No. Sorry I don't know how to do that without destroying the electronics in my car."
I think I'll purchase a rechargeable 'Booster Pack' for that purpose.
 

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Nice reply as usual Kevin, but OP has PHEV, not HEV.

To the OP, you have a small 12 volt lead acid battery inside behind a door right rear of your car. The intermittent charging of such batteries by numerous PHEV/BEVs brands leads to dead batteries and early battery failure. Your situation fits this scenario. Why the engineers designed systems like this is unknown, but you can make the battery less likely to fail and have an ordinary lifespan with regular maintenance per many forum posts on many makes and models of PHEV/BEVs. That is to run a smart trickle charger overnight (or longer) at least once a month. Affected owners often also get a portable jump charger as insurance so they won't get stranded again on a trip.

Of course, you should investigate possible issues of excessive drain which can cause dead batteries in any kind of car. In my case, I was twice burned by two different models of OBD readers left plugged in overnight. I don't leave one plugged in anymore.

Problems posted on forums doesn't mean this issue happens to all owners, but I suspect most owners will end up replacing that rather expensive small battery within two years without use of a smart trickle charger - for ICE cars with always charging alternators, batteries usually last 3 to 5 years.
Still trying to make sense of all this and I have a few questions:

1. Periodically when starting my phev in the morning I will see a message on the dash informing me that the Aux battery saver function was used to recharge the 12v battery. To me this sounds very similar to manually hooking up a smart 12v trickle charger overnight. Why would I need to use a smart trickle charger once a month if the car automatically recharges the 12v battery as needed?

2. I read in the user manual that you should not recharge the 12v battery while it is connected to the car's electrical system. So I assume this applies to a smart 12v trickle charger as well. And I guess when I disconnect the battery from the car I would lose various custom settings, radio presets, average mpg, etc.

3. I have been researching portable 12v Li ion jump starters. They rate them and compare them based on peak amps, total mA hr, etc. I have seen videos where they test various models cranking the engine of trucks, etc. But if the 12v battery in the Ioniq is only used to power the ctrl system electronics, not to crank the gas engine, then all of those specs seem to be overkill. Couldnt I buy a much less expensive model portable jump starter with much lower peak amps and mA hr ratings?

4. Over the years I have jump started two other cars from my Ioniq. Each time I have connected the jumper cables to the 12v battery in the trunk. Each time my car was running when the other car was being started. This week I read the Ioniq user manual and it says to connect the jumper cables to the + terminal and - chassis under the hood. And it also says my car should not be running when the other car is starting. I read the manual when I got the car but I have a bad memory. I guess I have been doing it wrong.
 
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