12v battery drained

[dbpianos]

(I posted about this on a recent YouTube video, but thought it might be useful as a topic here.)

I'd heard about the potential for the 12v battery to go flat unexpectedly but hoped it wouldn't happen to me. However, a few days ago it did, after only a couple of weeks of ownership. The car was supposed to be going in to the dealership that day for a separate reason, which at least gave them a chance to see this at the same time.

The first sign of trouble was that the doors wouldn't unlock with the key plip - ours doesn't have automatic door handles - but once in the vehicle (using the physical key) nothing would work. I realised that the 12v battery was a likely cause and after trying a number of more or less improvised solutions I called the AA , membership being included with our bank account. A battery booster pack was all that it took to start the car's electronics, at which point I put the vehicle into Utility Mode for a few minutes to bring up the battery voltage - it had been showing just 4v on my multimeter - and I then drove successfully to the dealer's.

I'll be collecting the car from the garage in the next day or so and I'll update this post accordingly, but anyway I've already invested in a battery booster (lithium ion battery with jump leads attached, basically) to keep in the glove compartment in case this happens again. EDIT - they didn't find anything wrong with the 12v battery and were unaware of this problem. I asked them to feed back to Hyundai UK.

I don't have any accessories plugged in, potentially draining the 12v battery. Others have queried whether the charging port cover is too snug and might press against the release button. The Bluelink connection could be another candidate, and using the boot lid must be quite a drain (if it uses the 12v system), but all of this requires the car to ignore the gradually depleting 12v battery and simply let it fail while sitting on enough energy in the high voltage battery to run a whole house for several days. It seems obvious to me that there is no reason for the 12v battery to only be charged when driving (or when in special modes), as unlike ICE vehicles we're not relying on a running engine and alternator as a power source. But I may be too simplistic in my thinking!

[holard]

Interesting to read about your battery drain. I have heard of several occurences of this problem. I would be interested to know which battery jump booster pack you purchased if you are prepared to divulge it.
I have tried to purchase a space saver wheel 19" without much success as I prefer a spare compared to the terrible "repair kits", are you aware of any such wheels?

[Chino2020]

Glad you posted the topic I've had the same issue after one year of driving my IONIQ 5 the 12v battery randomly goes flat.

I've also had the AA out and a simple boost tj the 12v got the car going again only to find the battery does not hold its charge. I did some further investigation and found the battery it's self has no issue, but something is pulling power from it when the car is turned off. I've done all the things mentioned in the online posts about changing Bluelink passwords although I've never used a third-party app. That's concludes the issue is something else and not the stuff Hyundai is saying that's draining the 12v.

[Burntcrisps2]

Have you booked it in for diagnostics and any software updates?
Pls. Update the thread with any resolution.

[Chino2020]

Does anyone know how much charge the 12v battery takes to fully charge when driving ? I drove the car for an hour's in the hope it will charge the 12v battery but when left for 30 mins it went flat again.

[Burntcrisps2]

I doubt an hour is long enough to fully charge a 12v battery.
It all depends on what the initial charge status is.

Have a look at this video and can recommend the BM2, they sell loads of them

[RACIONIC5]

Hi I had 12v battery drained overnight in Spain on a drive which wouldn't allow jump leads so called RACC the RAC equivalent in Catalonia. He used a boost box got it going then advised to keep car in start mode then drive for as long as possible eg over an hour.
What caused depletion, unknown then through the night alarm continuous presumed as I hadn't reset after ferry crossing in case of alarm activation by boat movement NO. Then as alarm went off again very large moth flying round in the car was setting off the alarm, moth dispatched, no further issue so it must have been the alarm, which we couldn't see or hear overnight, drained the 12v.

[RACIONIC5]

BTW the emergency key extracted from the key fob is very difficult to use as the space to insert in the opened flush door handle is very tight

[Davenport]

Hi, I have a 2022 Ioniq 5 and the 12v battery is dead. I can jump start it but 12v battery wont hold charge. I have been told to take in to dealership as battery under warranty but I dont have enough mileage. Can you charge nain batteries when 12v is dead? I have plugged in to my home 7kw charger but it just says waiting for ev. Also tried 13amp but doesnt charge so assume it needs some 12v power to kick in? Also can you lock car and shut charger flap manually or do I have to jump it again just to shut it?