Ioniq EV - what happens when the 12v battery dies?

Today the 12 volt battery died in our Ioniq EV. Had to call Hyundai for roadside assistance. Simple issue and a lesson learned, but why did the battery die even when ignition was on?

[@grantclark988]

Thanks for the post. Explained the reason that our second-hand 2017 Ioniq went epileptic on us with EXACTLY those symptoms. We'll get the 12-V battery changed and hope for the best. Lesson learned!

[@kravdraa7]

This appears to be a universal problem across many EV cars. This Hyundai, my Kia Soul, and another mentioned their Leaf, as examples, and I have read of many others. So the question is, why? There are a few possible answers, but most are very annoying. First, the size of the 12v battery is too small, and/or the quality is poor. If this is the main cause then it is deeply unsatisfactory and astonishingly bad manufacturing. Second, the charging system is inadequate, barely keeping the battery topped up through normal use. Again, such an implementation, presumably in a ridiculous effort to maximise distance, is unforgivable. Third, the integration between the 12v and 400v systems is badly designed. Some would ask why there even needs to be a 12v battery, so that we have this farcical message to turn the car on fully while just listening to the radio. I've sat in an ICE listening to a radio for well over an hour without the engine running and not causing the slightest difficulty, even though cranking such an engine needs far more power than starting an EV. I appreciate that the manufacturers may have decided a 12v battery and charger was cheaper and easier than a voltage control system to take that 12v feed from the drive battery, but the solution simply does not work well. Fourth, there is an 'unknown' drain on the battery. I have my suspicions that this may be at the root of some people's issue (me included!). The trick would be discovering that drain. While it may seem that nothing is on and the car is sitting completely 'off', I wonder if the key is within a certain distance (maybe 25 yards, or more, who knows?) that there is a constant 'dialogue' between key and car and it is this that drains the battery. Clearly, there has to be some communication going on for the key to register as you approach to trigger the mirrors, etc. If this is an active process that gets triggered more frequently when the signal is weaker then it could significantly add to any drain. Perhaps, the cars 'ears are pricked' with a very weak signal and then there is some form of rapid re-checking, made worse by a boosted signal. It's even possible that this is exacerbated should the spare fob be similarly close. It would take someone with the understanding of how these systems work and the equipment to check, but it would be an interesting thumbnail survey to find out how many people who have suffered these issues keep their keys at the front of the house, in some proximity, while the car is parked outside.

[@Hans-gb4mv]

Cars are not designed to run on the 12V battery. That battery is only designed to power on the car safely. You really want only low voltage to power on the electronics that can perform the safety checks before enabling the 400V battery. Because if something is wrong, you don't want that 400V to cause dangerous situations. EVs therefore have small batteries. They don't need the huge power for the starter engine, they only need the power for basic electronic operations. Why install a big heavy battery like you would have in a diesel engine when you never use that amount of power? If you want to run the accessories, you should turn on the ignition or, if your car has it, accesory mode so that the car keeps the 12V up from the 400V battery. The drain is probably with some of the electronics that keeps an eye on the battery. If needed be, most cars will protect the battery from either cold or heat. But you need power to keep monitoring those conditions.

[@maurice7413]

You saved me today. I bought a used 2017 Ioniq EV 3 days ago. Tires showed low, so I plugged my compressor into the 12v (Cigarette Lighter) plug and left for about 5 minutes. Came back and compressor was working weakly. Unplugged and got the key not detected, placed the key on the starter and got the stop and check brakes. Remembered this video, got my charger and charged the battery, lesson learned. Thank you !

[@supadan323]

This video may have saved me from a mental breakdown. We just got through Hurricane Ian. I though my car did ok, but it would not start. It started going through all the error messages at once, like your car did. I was afraid that it was going to be a huge, long lasting fix, but IF IF IF the symptoms match, hopefully its just a battery change. Wow thanks from 4 years later.

[@leadingwithautism]

Thank you for sharing Stewart. I had the exact same issue (caused by leaving the radio on with the ignition off) but I was able to easily diagnose the problem thanks to your video. I put a trickle charger on my 12v battery (luckily I was at home) and after a few hours the 12v battery was charged enough that I could turn on the car and the main battery charged it the rest of the way.

[@larrydunkelman4478]

It’s advisable to keep a battery booster in your car - even for ICE vehicles. It would get you on your way in no time. The main battery will recharge the 12v battery but only over night when parked.

[@brianoc1]

Thanks for you video. This has now happened twice to me. Each time I was guilty of leaving the Interior lights on after multiple phone calls etc... Before going in the house. Next day... Full battery, and dead 12 volt. Something fishy. Just bought a cigarette lighter with volt readout. Thank you for clearifing and validating how it works. Cheers.

[@FancyaBevMate]

Thanks for this stuart, I messaged ryan (ev opinion) a week or so ago because you can by just pressing the start button without your foot on the brake gain access to just ancillary items but I was worried that the 12v might just go flat and while I didn't expect your issues I did think I wouldn't be able to use the lights, indicators and other 12v items. Cheers for bringing this up.

[@Dr-EV]

This has just happened to me today. Parked up at work for 8 hours. My 38kwh 1 year old ioniq first showed signs of flat battery when the wing mirrors unfolded very slowly. Thankfully central locking operated. Pressed the brake pedal to start it up and the pedal gave an ABS type vibration and noise. The dash didn't illuminate. The car then seemed to loose all power soon after with even interior light unable to illuminate. AA breakdown guy said the batter was at 6 volts and very quickly dropped to 2 volts..... Oooo. His tester also said the battery had failed, it just hit 12 months old at 9772 miles. A quick boost from his pack was enough for me to get up and running as well. But why would a fully shutdown and locked car deplete it's 12v so quickly? Not sure if related but got a software update to fix radio issues last week. Radio is now great and has completely new GUI, I wonder if other software was updated that may be buggy.

[@lhs112]

Had same problem with my Ioniq 4 times now. Happens just by being parked over night. It's coming up for 5000 km service (first one) and i will ask Hyundai to replace and install a battery if better quality. Reading online seems the stock Ioniq 12v battery is of poor quality.

[@TheAlexvistian]

Thanks Stuart !! You saved my morning! Was already planinng to call hyunday asist. In my case i left the road lights (led) on overnight.

[@ukwhitewitch]

Stuart, first of all thank you for your videos, they are most helpful. A couple of questions if you don't mind. Firstly the manual says never connect a charger to the 12V battery while it is still connected. I want to connect a 3.5amp CTEK recondioner and trickle charger to my 12V battery without the faff of having to disconnect it, and then reset all the electrics in the vehicle. Hyundai say it is a no no, but I can't understand how it is safe to pass a whacking great charge from a battery booster, or jump cables to a connected battery, but not snail charge with a trickle charger. What is your opinion on this please? Secondly, you mention the Ioniq EV charges the 12V battery when in READY mode, but it also charges it indefinitely with 20 minute pulse charges from the main battery when required, provided the Battery Saver + option is ticked in settings, and there is sufficient charge in the main battery. I have seen this happen a few times with my car - the third LED on top of the dash flashes on and off whilst it is doing it, and I get a message next time I start the car to say the Battery Saver + feature has been active. At first I thought this feature was limited to10 cycles before disabling itself, but this only happens if the Batter Save + kicks in when the car is in Ready mode. I'm really shocked that you put the car in READY mode as soon as the battery warning appeared, but instead of charging the 12V battery, it was too late to prevent a breakdown because it had already discharged so much. Maybe Hyundai should update the software to give a battery warning a lot sooner, or perhaps enable 12V battery charging when the ignition is in AUX mode too. I'd be interested to hear your thoughts.

[@waqar7720022]

Thank so much for making the video to understand the issue. It's happened to my car the same. You are star

[@Rhaman68]

One of the reasons a 12 Volt battery fails on a new car is a defective battery. When one or two cells cannot hold a charge it will not hold enough of a charge. The factory 12v battery on my 2011 Nissan Leaf lasted six years. Some strange messages on dashboard told me something was going on but no direct link to the battery. If only EVs had a system to report issues with the battery. Thanks

[@allerton12005]

Have you turned the Auxiliary battery saver to on

[@hugorhodano8428]

Hi Stuart, thanks for sharing. Is there no 12V battery run out warning? 2018 Ioniq hybrid has no lead 12 battery anymore. Instead there is a small lithiumionbattery in the main battery pack. On the cockpit there is a button for emergency if 12 battery run out. If You push that button, the small 12V battery will charged from main battery. I hope Hyundai will integrate it in all variants of Ioniq family.

[@Drogos79]

u didn't watch the video, did you

[@thrustsst]

I have seen all your videos about IONIQ Electric in recent days and I think every of them has been informative and very interesting. I hope you will proceed and continue with your videos about IONIQ Electric. It could be interesting if you could review some of the many smart features that this car contains; dynamic cruise control, lane assistant, regenerative braking, locking the car etc. I do not have an electric car though but considering an IONIQ Electric. However, the conditions for electric cars are difficult in Denmark. The delivery time for IONIQ Electric is 9 months and probably one of the disadvantages of getting more people to buy electric cars. For my use, most electric cars have that major disadvantage that a towing hook cannot be mounted. So goodbye to trailer and caravan happiness. In Denmark, 50% of all electrical power is supplied by wind turbines, and one should think that it would be the ideal place for electric cars, but the Danish government does not really care what type of car people choose to buy. If people think about buying an electric car, they can do it if they like, but in the opinion of the government, it would rather not be a luxury electric car. As the number of Tesla's in 2015 apparently became a little too high...... !, it was decided to introduce taxes on all electric cars - those who previously had been tax-free. This has largely stopped the sale of electric cars, and the infrastructure is also not much in focus on the fact that electric car sales have gone back so strongly. If Denmark - if ever - comes close to the neighboring countries regarding electric cars, is very hard to guess - but it does not look too bright - and that's a shame.

[@StuartDWright]

Surprising. I thought Denmark was a progressive, foreward thinking country. Thanks.

[@thrustsst]

Thanks for your reply and keep up your good work with - hopefully - more interesting videos about the IONIQ Electric.

[@tanzanable]

Thrust sst - Why are they punishing electric cars with new high taxes?

[@thrustsst]

The government argument is quite simple: When paying car tax you get roads, bridges and all that stuf which is required for privat trafic. EV's should also contribute to that - they say ! To be honest: There many factors that have influence of the final tax-pay - so in practice it means less tax than on fossil-cars which of course is quite sensible.

[@michaelgoode9555]

When the Danes elected a more right wing government a few years ago it signalled a shift from new technologies back to dirty fossil and the profit motive. People should really be aware that their "favourite" Christian nationalist government are in fact their worst enemy. Sweden are making a similar mistake now. Why are western countries going all right wing? Ah yes, ageing populations and simple greed. It never works out well but ageing bigots are the same world over.

[@Wendy-dk1sp]

I had this exact same thing happen today and our 12v battery is relatively new. Apparently, it's quite common and Hyundai have no answers. We're not impressed.

[@nickhickson8738]

How on earth can this happen by sitting in a car for an hour? Surely the car's electronics should keep this relatively new 12v battery topped up, sufficient to support this scenario. It is rubbish if it does not.

[@Rhaman68]

Nick Hickson Hi, I believe the Ioniq dies not have a normal 12v lead acid battery. As to powering the car without the main battery that is never recommended as the main battery hardly discharges just powering while "idling." My 2011 Nissan Leaf hardly registers a discharge doing just that. Everyone must read the car manual for limitations. Thanks

[@Peter-st1lt]

Thanks Stuart great info much appreciated Cheers!

[@soaring9379]

The same happened to me last week, its booked in for an upgraded battery.

[@andrewmcmahon2464]

From Hyundai or aftermarket

[@acastanaz]

Thank you for the advice.

[@gregoryosullivan]

What accessories did you have running that drained the battery so quickly?

[@StuartDWright]

The radio and the heater.

[@ITubeTooInc]

They should have designed the Ioniq so the heater turns off if you turn off the ignition then, because the heater uses a lot of power. The radio use very little power in comparison.

[@tarassu]

You can't run the heater. Or... you can run the fan but there will be no heat. So what was actually running?

[@stephenhulbert3500]

This was (is still?) a well-known problem with the first generation Nissan Leaf. Randomly and rarely, owners would find that their car was completely dead, often centrally locked. Even the charging port could not be opened. Owners sometimes had 12V batteries replaced under warranty (I did). I don't believe a root cause was ever found.

[@FranFirman]

For the car to charge the 12 volt battery, the car has to be in running mode, not just ignition being on. ie the green car icon has to be lit. Then it will keep the 12 volt battery charged.. Or as I have been told. This is also how you can run emergency lights etc from the car when there is a power cut, with a small 12 volt inverter attached to the battery, and the car turned on to keep it all charged. For the Leaf the inverter can be up to 1KW.

[@ratgreen]

I just noticed your other video where you ran out of charge, you can see when the car shuts off and your dash cam drops to low 11v almost immediately. Thats a pretty sure sign your 12v battery is dead and needs replacing. This is another vote in my head that says EV's should have small solar panels to keep the 12v battery charged. I think if I ever get one, I'll be installing some solar, just to avoid situations like this.

[@barriedear5990]

One of the Nissan Leaf's has a small solar panel on rear spoiler for this.

[@washubrain]

I'm not sure if this is relevant for the Ioniq hybrid but thank you for the advice any way :)

[@dorsetengineering]

Interesting.... so the dc-dc converter only runs when the ignition is on? On the ampera it runs regularly when the ignition is off to keep the 12v topped off. They suggest you leave it with 1/2 charge for example when leaving it at the airport etc. Tesla the same I understand.

[@dae3xt]

does your 12 volt battery still work or did you get that replaced after several years from making of this video? Any info. appreciated. My Thanks. The replacement battery is very expensive $580 US dollars.

[@apkungen89]

Great vid. How do I know if the ignition is on or not? It's not like the motor is running.

[@StuartDWright]

The dash lights come on to indicate that all systems are go.

[@stalwart56k]

Have you had any other trouble with your battery dying?

[@joeysokool]

Thank .... this happen to me today .....

[@thyresias194]

Hi, may be the gulty is your dash cam on parking mode with continue 12 volts

[@StuartDWright]

No, the dash cam has a setting to switch off when in parking mode if the battery voltage drops below 12 volts.

[@thyresias194]

Thanks for your videos, I order my ioniq electric in February but 5 months delai if I'm lucky ;-)

[@three60five98]

Seems like the car company is using paying customers to do their R&D about their battery problems. This problem also stretches to the far east. It does not sound good.

[@adamyusof]

Did the problem occur when you stay in the car with the engine switch off and you switch on radio unit, is it cause the 12v battery drained to 6v?

[@StuartDWright]

There is no engine :) The radio was on but the ignition was off so yes, it quickly drained to 6v

[@esenel92]

doesnt the electric version have a 12v reset button next to the steeringwheel? Or is that just for HEV?

[@StuartDWright]

It's not on the EV.

[@Dreadpirateflappy]

I just ordered a hybrid version, what does the 12v reset button do?

[@esenel92]

Steve, it seems to bypass the battery saving mode that kicks in once the voltage on the 12v battery gets too low. From what Ive read the system then disconnects the 12v battery to prevent deep discharge, and the reset button then disables that safeguard allowing the battery to be used. Some ioniq's seem to have it, others don't.

[@lhs112]

esenel92 as far as I know only the hybrid or PHEV versions have this reset button.

[@FHB71]

I assume this is also the case in the PHEV.

[@StuartDWright]

No idea about that version. It has a petrol engine, so maybe not.

[@FHB71]

Yes, it does, but it operates like an EV, the ICE is only used when it requires more power or when the battery runs low, otherwise you are driving (within the 60km range) almost only with the EV.

[@milensemerdzhiev7929]

I had exactly the same issue today and then the battery died completely. I have plugin hybrid

[@ahmedtauseef]

time to change the 12V battery if it is more than 3 years old

[@chrispatterson8073]

Planned Obsolescence, like an IPhone update. Mic drop.

[@StuartDWright]

It’s the 12v battery, not the main high voltage battery and it ran flat because I sat in the car with the radio on. Pick the mic up and try again.

[@cbcdesign001]

Hyundai are absolutely useless at producing a reliable 12V system on their EVs. Even the latest expensive Ioniq 5 has 12V issues. That they cannot monitor the 12V battery CONSTANTLY using an insignificant low amount of power (easily achievable with modern electronics and high input impedance semiconductors) and automatically recharge the 12V battery FULLY when it falls below a minimum level, with all the power available in the traction battery beggars belief. I NEVER had issues with the 12V batteries in my Fossil cars, my Ioniq EV on the other hand has failed on me TWICE!

[@bitmanev4331]

nothing new and the same if used an ICE for hours without the engine on...

[@StuartDWright]

It was less than an hour.

[@Rhaman68]

bitman EV hours? Try 30 to 40 minutes! For EVs there is no reason not to use the main battery always. The accessories draw very little due to the size and power of the battery. Thanks