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2022 Ioniq 5 SEL AWD Lucid Blue
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So I had the dreaded dead 12V battery today. I went past my Ioniq to go out via the garage to check the mail mid day today and knew something was up because the single red strip of light underneath the brake lights/Ioniq 5 lettering was lit. I was like hmm, that seems weird and unusual. Tried to open the car door and no response, so as I suspected, dead 12V. Needed to use the mechanical key to open the door, pop the hood, and get the 12V jump start battery from the glove box. Connected the 12V jump starter to the battery and started hearing some clicking noises, I suspect I could have disconnected the jump start battery then but I went ahead and turned on the car first. Oh, and the alarm started honking at me as soon as the 12V was live, not sure if closing the driver's door would have prevented it but just be aware so you don't startle yourself.

Not entirely sure what caused it to go dead. I realized I left the lights on (not in auto like normal) as it was raining but bright enough for auto lights not to be on yesterday when I drove it. I assume those turn themselves off though like on most modern cars. Other than that, I have a hardwired dash cam but it has a low voltage cutoff switch and an OBD dongle that does stay on even when car is off. Would love to know why the 12V died but not sure I'll ever know.

One more thing, I wasn't getting any response from the lock/unlock button on the passenger side door handle this evening, but the driver's side was fine. I suspected it might need a reset, so I disconnected the negative terminal on the 12V battery when i got home, reconnected it and worked like a charm afterwards.

Any ideas what drained my 12V battery? Anyone else had similar issues with the lock/unlock button after a dead 12V?
 

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So I had the dreaded dead 12V battery today. I went past my Ioniq to go out via the garage to check the mail mid day today and knew something was up because the single red strip of light underneath the brake lights/Ioniq 5 lettering was lit. I was like hmm, that seems weird and unusual. Tried to open the car door and no response, so as I suspected, dead 12V. Needed to use the mechanical key to open the door, pop the hood, and get the 12V jump start battery from the glove box. Connected the 12V jump starter to the battery and started hearing some clicking noises, I suspect I could have disconnected the jump start battery then but I went ahead and turned on the car first. Oh, and the alarm started honking at me as soon as the 12V was live, not sure if closing the driver's door would have prevented it but just be aware so you don't startle yourself.

Not entirely sure what caused it to go dead. I realized I left the lights on (not in auto like normal) as it was raining but bright enough for auto lights not to be on yesterday when I drove it. I assume those turn themselves off though like on most modern cars. Other than that, I have a hardwired dash cam but it has a low voltage cutoff switch and an OBD dongle that does stay on even when car is off. Would love to know why the 12V died but not sure I'll ever know.

One more thing, I wasn't getting any response from the lock/unlock button on the passenger side door handle this evening, but the driver's side was fine. I suspected it might need a reset, so I disconnected the negative terminal on the 12V battery when i got home, reconnected it and worked like a charm afterwards.

Any ideas what drained my 12V battery? Anyone else had similar issues with the lock/unlock button after a dead 12V?
Have you got a BM2 battery monitor fitted? Useful to have as it will help to show you what happened.
 

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I have a PHEV but experienced basically an identical situation with needing to use the manual lock and then having the alarm go off when it started to come back to life.
Best conclusion I was able to get is I was using my 12v battery for too much without it getting any recharging back into it. Most days the gas engine doesn't turn on in my car, so the alternator doesn't get to cycle the battery. And I'm using heated seats / cell phone charger / etc - what I came to find out is that is un off the 12v and the traction battery is essentially just for driving. Don't crucify me if I have any part of that mixed up- but that's what I've come to understand.

Fix? I installed a battery tender on the 12v and I hook it up to the wall charger once a month or so for a few hours for peace of mind.
 

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Man, the irony of legacy auto technology.... Here we have a big old 77kwh battery pack (or 56? kwh if you have the smaller pack) full of juice, and then everything is run by the ol' 12V accessory battery (probably lead acid.. although I didn't check before I started writing this response). I've read of many other EV owners having their cars stuck because the 12V battery died. It seemed crazy to me that the manufacturers didn't just use a DC-DC converter to power everything off the main pack until I remembered that a DC-DC converter costs hundreds of $'s (or more) whereas a standard lead acid battery costs $10's of dollars.

One thing I might look into is replacing my 12V battery (assuming it's lead acid) with an LiFePO4 battery which will hold charge a LOT longer, LAST a LOT longer (battery lifespan), and have a lot better C-rate in cases where I need to jump start someone else's car.
 

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Man, the irony of legacy auto technology.... Here we have a big old 77kwh battery pack (or 56? kwh if you have the smaller pack) full of juice, and then everything is run by the ol' 12V accessory battery (probably lead acid.. although I didn't check before I started writing this response). I've read of many other EV owners having their cars stuck because the 12V battery died. It seemed crazy to me that the manufacturers didn't just use a DC-DC converter to power everything off the main pack until I remembered that a DC-DC converter costs hundreds of $'s (or more) whereas a standard lead acid battery costs $10's of dollars.

One thing I might look into is replacing my 12V battery (assuming it's lead acid) with an LiFePO4 battery which will hold charge a LOT longer, LAST a LOT longer (battery lifespan), and have a lot better C-rate in cases where I need to jump start someone else's car.
But there is not really a problem with the current 12v battery. Battery failures identified so far can be attributed to a specific defect with the car, such as the charging door, or with the operator such as using the infotainment system for a while without being in Ready of Utility mode. The car does regularly top up the 12v battery from the HV battery.
 

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But there is not really a problem with the current 12v battery. Battery failures identified so far can be attributed to a specific defect with the car, such as the charging door, or with the operator such as using the infotainment system for a while without being in Ready of Utility mode. The car does regularly top up the 12v battery from the HV battery.
Sorry I was not clear. I was just thinking about using an LiFePO4 battery because it withstands those "defect" conditions (where the car fails to top up the battery, or an accessory is left active overnight) better than a similar size lead acid battery because of the much higher energy density. Essentially, you have a much larger reservoir of energy in the battery for those "oops" situations..
 

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Sorry I was not clear. I was just thinking about using an LiFePO4 battery because it withstands those "defect" conditions (where the car fails to top up the battery, or an accessory is left active overnight) better than a similar size lead acid battery. Essentially, you have a much larger reservoir of energy in the battery for those "oops" situations..
Sure, but some of those conditions were drawing 9 amps so you would need a huge battery to supply that for hours!
 

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Sure, but some of those conditions were drawing 9 amps so you would need a huge battery to supply that for hours!
Yeah, it's not going to handle every situation of course. But as an example, I replaced the 12V Lead acid battery on my Subaru with a LiFePO4 battery (that had 4x the AH rating, but was the same physical size) NINE years ago, and it's still going strong even though my daughter and son both have accidentally left the headlights on ALL NIGHT a few times (don't ask.... ugh...lol).

It might not save you from getting your car temporarily "bricked" in some situations, but it has definitely saved us from morning "oh no" headaches several times.
 

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Yeah, it's not going to handle every situation of course. But as an example, I replaced the 12V Lead acid battery on my Subaru with a LiFePO4 battery (that had 4x the AH rating, but was the same physical size) NINE years ago, and it's still going strong even though my daughter and son both have accidentally left the headlights on ALL NIGHT a few times (don't ask.... ugh...lol).

It might not save you from getting your car temporarily "bricked" in some situations, but it has definitely saved us from morning "oh no" headaches several times.
if you find one I’m in, but I’ll be looking myself as well.
 

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This company may have the correct size for Ioniq 5. The link is for Ioniq classic 12-volt battery.
This LiFePO4 battery will be damaged if charged and stored in freezing temperatures.
If you read product specification:
Charge Temperature: 0 to 45 ºC ( 32 to 113 º F )
Recommended Storage Temperature: -5 to 35 ºC ( 23 to 95 º F )

Ioniq 5 doesn't know it and will push many amps after start, regardless of battery temperature. Moreover, the BMS cutoff voltage is 14.8V, Ioniq5 sometimes may charge battery with higher voltage.
 

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This LiFePO4 battery will be damaged if charged and stored in freezing temperatures.
If you read product specification:
Charge Temperature: 0 to 45 ºC ( 32 to 113 º F )
Recommended Storage Temperature: -5 to 35 ºC ( 23 to 95 º F )

Ioniq 5 doesn't know it and will push many amps after start, regardless of battery temperature. Moreover, the BMS cutoff voltage is 14.8V, Ioniq5 sometimes may charge battery with higher voltage.
Not that I want to get into an argument, but lead acid is worse in cold weather (and hot weather for that matter).


LiFePO4 is a superior chemistry in every way when it comes to charge and discharge characteristics.


Also, the charge voltage for LiFePO4 is 3.7V, so a 4S pack has a charge voltage of 14.8V which drops down to 3.2V per cell nominal yielding 12.8V nominal for a 4S pack. You can charge LiFePO4 chemistry up to 4.2V per cell, which means a 4S pack will take 16.8V no problem.

BTW, your car doesn't "push" current, it draws it. And pretty much every LiFePO4 cell will take a full C with no sweat whereas a typical automotive lead acid battery (not deep cycle) will rapidly degrade under anything over 1/10th C. So if your car is drawing extra current for some reason, you are FAR better off with LiFePO4 than with standard lead acid.

The downside is that LiFePO4 batteries are more expensive than standard lead acid. But they make up for that in superior characteristics and life span. You will end up replacing lead acid batteries many times over the span of time it takes for a single LiFePO4 battery pack to reach end of life.
 

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Red 2019 Ioniq 38 Premium EV
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... seemed crazy to me that the manufacturers didn't just use a DC-DC converter to power everything off the main pack until I remembered that a DC-DC converter costs hundreds of $'s (or more) whereas a standard lead acid battery costs $10's of dollars.
The reason you have a separate 12V is that you need to be able to operate things like hazard warning flashers etc if the car's broken down, detected some major failure in the 400V battery system that could electrocute people, and so has opened the contactors to isolate the HV & protect everyone. Even if a fireman's spraying water everywhere. And that's where there's a special bit of cable somewhere in EVs, may be in the boot, may be under the bonnet, that firemen can cut with insulated bolt-cutters to make really, really, sure the HV's isolated, in a major accident situation.

You also need some power source to boot up the car & pull the contactors in when you switch on to drive, so the 12V also does all that.
 

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BTW, your car doesn't "push" current, it draws it.
Actually both, aux battery is charged while driving.

Yes, LiFEPO4 is superior in many ways, but has rather narrow temperature span, not suitable for all uses in all regions. According to technical spec, this battery is not intended for storing below -5ºC or over 35ºC (23 - 95ºF) and can only be charged between 0ºC to 45ºC (32 to 113ºF). If your winter nights are milder that 23ºF, you may go for it. But then probably the battery heats up to over 113ºF under the hood in summer, especially if car sits in the sun...
 

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This has now happened to me 3 times, each time the car had received an OTA update either that day or the day before, which i assumes runs down the 12v. I don't do much miles and therefore only charge up about once a week which doesn't seem to be helping.
 

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This has now happened to me 3 times, each time the car had received an OTA update either that day or the day before, which i assumes runs down the 12v. I don't do much miles and therefore only charge up about once a week which doesn't seem to be helping.
I do not think the car has received any OTA updates yet. If you have had the 12v fail 3 times there must be a fault, unless you are leaving things switched on.
 

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I do not think the car has received any OTA updates yet. If you have had the 12v fail 3 times there must be a fault, unless you are leaving things switched on.
I've received 3 updates on my P45, it was enabled in January and I have had 1 update in Feb and 2 in March. It's obvious when it happens as you have to agree to new terms and conditions along with a new privacy statement, the first time it reset some settings as well. No other fault as it works perfectly until an update, I only had the non starting issue once previously before i had the firmware updated so I know it isn't the battery.
 
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