That sounds slick, but portable lithium-ion jumpstarters are cheap and extremely reliable. I wouldn't risk needing to go plug something in somewhere when there's an available option that you can keep fully charged in your frunk and that will save you (or more likely, lots of other people you encounter) anywhere. I'm not sure about the I5, but the gas cars I've jumped often need a sustained current if the 12V is very dead and I wonder if a capacitor would work long enough.

 

The selling point of the "batteryless" models is that they do not need to be charged, they scavenge enough juice from the sying battery, store it in the capacitors, and then use it to start the vehicle. One question is when the Ioniq5 "dead 12v battery syndrome" strikes, is there enough juice left in the battery to feed the unit, IIRC it needs the battery to be at 8V or so.

 

Since 2016, I always carry a GB40, simple, and can power USB devices in a pinch too: NOCO Boost Plus GB40 1000 Amp 12-Volt UltraSafe Lithium Jump Starter Box, Car Battery Booster Pack, Portable Power Bank Charger, and Jumper Cables for up to 6-Liter Gasoline and 3-Liter Diesel Engines

The slight irony is that despite my fascination with 12V system problems, I have never yet had to use it to start an EV.

 

Since 2016, I always carry a GB40, simple, and can power USB devices in a pinch too: NOCO Boost Plus GB40 1000 Amp 12-Volt UltraSafe Lithium Jump Starter Box, Car Battery Booster Pack, Portable Power Bank Charger, and Jumper Cables for up to 6-Liter Gasoline and 3-Liter Diesel Engines

The slight irony is that despite my fascination with 12V system problems, I have never yet had to use it to start an EV.

After reading about all the issues with the 12v battery in the Ioniq 5 I purchased a 12v Lithium jump start box which I keep in the frunk of my car.

I have used it once: After a meeting I was at another attendee found the 12v battery in their Prius was dead. I was able to use my 12v jump pack to get them going.

 

With an EV you don’t need much. No mechanicals to turn over so don’t need a lot of amps BUT might as well get a good one that can crank an ICE.

this guy does great unbiased reviews/tests

 

FWIW I've had 2 vampire drains on my Ioniq 38 that left the 12V sitting at 8.4V . I rather doubt there would be enough left in that to charge up a capacitor-based device sufficiently to get the contactors pulled in & the car started.
I decided to make my own built-in booster pack, based on 12V 20 Ah slim motorcycle battery + electronics, strapped to existing under he bonnet. Works just like a booster pack, except pre-wired ready for instant switchover.