12v battery drained

Faults and Technical chat for the Hyundai Ioniq 5
Post Reply
Posts: 2
Joined: Thu Apr 21, 2022 1:33 pm

Post by dbpianos » Thu Apr 21, 2022 2:16 pm

(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!

Posts: 2
Joined: Tue Apr 26, 2022 3:47 pm

Post by holard » Tue Apr 26, 2022 3:56 pm

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?

Post Reply