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Dear All
I've been having problems with the 12v auxiliary battery in my 2019 Ioniq BEV. Shortly before Christmas I drove the car for around 30 minutes and then sat in it for 2 hours while connected to a level 2 charger (with ignition off); at times I switched on HVAC as the windows misted up. I then drove 20 miles home and the car behaved perfectly normally. Next day I tried to start it but there was zero response and ended up calling Hyundai/AA Rescue who diagnosed a flat 12v aux battery, jumpstarted it and recommended I leave the car switched on in P for a couple of hours to let it recharge fully from the high voltage battery. Since then I've been monitoring the 12v battery using a multi meter with the ignition switched off and it never achieves more than 12.3v and frequently drops to 12.1v which seems very low to me; with the ignition on it reads around 14.7v. It makes no difference how often the car is driven or how long it's left sitting on the drive switched on in P: it never gets higher than 12.3v. The aux battery saver function has been enabled since day 1 and although I'd noticed the blue dash light flashing at times in the weeks before the problems started, I've not seen it since and never seen any dash message to say it's been on. The car has been starting normally, but at no more than 12.3v, I'm not convinced that it would take much for the battery to fail again. Covid-19 permitting, the dealer is going to test it at end of this month, but in the meantime I wonder whether anyone has any thoughts or similar experiences. Thanks!
 

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Hi
I've had similar problems, my 38 has been into the dealer about 4 times for a flat 12v, the last time back in about October last year they diagnosed a fault where water dripping through the passenger side doors was sitting on unprotected electrical contacts on the locks, shorting them out and thus keeping the car awake. This was prompted by the fact that the last time it happened the pass doors were unlocked even though the drivers side doors were locked and that flagged as an error message for the passenger doors. The previous 3 times they couldn't find any causes, possibly as the water had fallen away from the electrics by the time they got the car to check out? The 12v was replaced after the second time as it had been flattened so badly. Most of these occurrences were after rain. The passenger side has been fixed by waterproofing the contacts but they wouldn't check the drivers doors for a similar fault as that side wasn't showing an error message which I wasn't very happy about. Was yours after rain or washing the car? I have been using a BM2 to monitor the 12v, and the battery saver charges the 12v once a day, I do see the blue light when its charging, but have never seen a dash message to say it's worked. BTW the "key fob in range" and "the USB/plug in voltmeter left plugged in" theories have been debunked as possible causes by the dealer.
 

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I've been monitoring the 12v battery using a multi meter with the ignition switched off and it never achieves more than 12.3v and frequently drops to 12.1v which seems very low to me; with the ignition on it reads around 14.7v.
There is nothing wrong with those voltages. The 14.7V you measured is its charging voltage, it is supposed to be some 2V higher than the batteries open clamp voltage so that is fine. And 12.3V open clamp or small load is just fine.
 

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Discussion Starter #4
Hi
I've had similar problems, my 38 has been into the dealer about 4 times for a flat 12v, the last time back in about October last year they diagnosed a fault where water dripping through the passenger side doors was sitting on unprotected electrical contacts on the locks, shorting them out and thus keeping the car awake. This was prompted by the fact that the last time it happened the pass doors were unlocked even though the drivers side doors were locked and that flagged as an error message for the passenger doors. The previous 3 times they couldn't find any causes, possibly as the water had fallen away from the electrics by the time they got the car to check out? The 12v was replaced after the second time as it had been flattened so badly. Most of these occurrences were after rain. The passenger side has been fixed by waterproofing the contacts but they wouldn't check the drivers doors for a similar fault as that side wasn't showing an error message which I wasn't very happy about. Was yours after rain or washing the car? I have been using a BM2 to monitor the 12v, and the battery saver charges the 12v once a day, I do see the blue light when its charging, but have never seen a dash message to say it's worked. BTW the "key fob in range" and "the USB/plug in voltmeter left plugged in" theories have been debunked as possible causes by the dealer.
Thanks for that Pete. The day before the battery died was really, really wet. I'll make a point of mentioning your experience when it goes in at the end of the month for testing. Cheers.
 

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Discussion Starter #5
There is nothing wrong with those voltages. The 14.7V you measured is its charging voltage, it is supposed to be some 2V higher than the batteries open clamp voltage so that is fine. And 12.3V open clamp or small load is just fine.
That's interesting; thanks for taking the trouble to respond. Since I hadn't been measuring the voltage before the problem and hence had no baseline, it did occur to me that this might not be an abnormal level after all. My concern was simply based on the assumption that 12.2v indicates a battery that is only 50% charged and since it seems to keep heading towards 12.0v I've been concerned that it'll let me down again.
 

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Keep the ignition on while you are in it, that will keep the 12v battery charged up whilst taking any power needed for accessories, including the periodic use of the HVAC and you'll not burden the 12v battery.
 
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Keep the ignition on while you are in it, that will keep the 12v battery charged up whilst taking any power needed for accessories, including the periodic use of the HVAC and you'll not burden the 12v battery.
As I found to my dismay when using electric pump to put extra air in the tyres.
 

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Thanks for that Pete. The day before the battery died was really, really wet. I'll make a point of mentioning your experience when it goes in at the end of the month for testing. Cheers.
You could mention Bristol Hyundai and the mechanic was Steve, in case one mechanic is allowed to talk to another, he generally seems good as he is happy to tell you exactly what he found and doesn't jump to conclusions
 

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My 2018 28kWh tells me a message on the dash after turning the car off but still sitting in it (infotainment screen still on playing music) and before opening the door (which would turn off the infotainment) that there is a risk of discharging the AUX battery (12v). Do the 2020's display this message too?
 

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Yes it does soon flag up a warning if you are using the 12v without any charging going on, I think it's tells you to switch to aux mode?
 

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My 2018 28kWh tells me a message on the dash after turning the car off but still sitting in it (infotainment screen still on playing music) and before opening the door (which would turn off the infotainment) that there is a risk of discharging the AUX battery (12v). Do the 2020's display this message too?
Yes in our 2020 it does but mostly only when I get in the car to record charging sessions and turn it on to ACC, hitting start twice without foot on the break. Not very often as you say after turning car off, music still going before opening the door.
 

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Ioniq 38kwh 2020
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. Since then I've been monitoring the 12v battery using a multi meter with the ignition switched off and it never achieves more than 12.3v and frequently drops to 12.1v which seems very low to me; with the ignition on it reads around 14.7v.
Just bear in mind that whilst measuring it with the bonnet open, the "bonnet open switch" causes the dash display to stay on, which causes a bit of a drain and causes the 12V battery voltage to drop. If you push the switch in next to the bonnet catch (so the car thinks it is closed) the voltage should creep back up.
 
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The drain of the dashboard can't be that much; a typical power supply for automotive dashboards is capable of delivering like 8W or so. If you notice a voltage drop over a couple of mV due to the bonnet being open it might be wise to replace the battery anyway.
 

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The drain of the dashboard can't be that much; a typical power supply for automotive dashboards is capable of delivering like 8W or so. If you notice a voltage drop over a couple of mV due to the bonnet being open it might be wise to replace the battery anyway.
Yeah, it I suppose it shouldn't in theory, but it could be leaving other electrical systems active causing a larger drain than just the screen, but mine shows about 12.3V whenever I've measured it, hold in the bonnet switch and it does rise to 12.5V+. Touch wood I've not had any issues with my battery to date.
 

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In my PHEV, car takes about 3A during 10 minutes or so before going to sleep, in several steps so maybe several computers are kept on while anything is on/open. (OT: My 12V battery is in the trunk, so I fake close it with a screw driver in the lock mechanism if I want to measure the 12V while making the car think it's closed.)
 

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In my PHEV, car takes about 3A during 10 minutes or so before going to sleep, in several steps so maybe several computers are kept on while anything is on/open. (OT: My 12V battery is in the trunk, so I fake close it with a screw driver in the lock mechanism if I want to measure the 12V while making the car think it's closed.)
3A, that's just 36W. Interior lights and probably DRL is all.

A 12V traction battery can easily deliver 440A and up to 550A when starting your PHEV, if 3A is a problem there's something very wrong.
 

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3A, that's just 36W. Interior lights and probably DRL is all.

A 12V traction battery can easily deliver 440A and up to 550A when starting your PHEV, if 3A is a problem there's something very wrong.
It's not a problem, only when measuring the voltage. The EV battery is quite small, about 40ah. 3A would flatten it in 13 hours. See the other threads on here about flattened batteries where the car hasn't gone to sleep properly.
 

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3A, that's just 36W. Interior lights and probably DRL is all.

A 12V traction battery can easily deliver 440A and up to 550A when starting your PHEV, if 3A is a problem there's something very wrong.
No, 3A is when everything apparently off, while a couple of ECUs figuring how to go to bed. That does pull down the voltage a few tenths of a volt compared to the resting OCV. The current then drops to 20-25 mA after those 10 or so minutes. The EV might behave differently of course. Not arguing, just throwing in some possibly relevant behavioural data from one car. Starting it takes 30A max iirc, it's not cranking an engine.
 

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Discussion Starter #20
Keep the ignition on while you are in it, that will keep the 12v battery charged up whilst taking any power needed for accessories, including the periodic use of the HVAC and you'll not burden the 12v battery.
Definitely making a point of keeping the ignition on whenever I'm sitting in the car. Also wondering how much drain Bluelink puts on the aux battery too; the car's electronics are never actually 100% powered off.
 
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