Yesterday, while finishing a hike with my Valentine, she spotted something I’d never seen before. “Hey David, what’s that green light on that parked car?” I turned to see a tiny green LED at the nose of a Hyundai Kona EV, inside its badge. The car appeared to be off and unoccupied. “Wait… did that car just turn that light on by itself?” I wondered. Sadly, I had no answer for my date, because I had absolutely no clue what this LED was all about.
The car was parked just outside of LA’s Will Rogers state park, named so because the land once belonged to early-1900s actor/radio host/writer/social commentator Will Rogers. My girlfriend and I had just descended one of the Santa Monica mountains after just missing the sunset, and things were getting dark. As we approached her Lexus RX350 in the parking area, she noticed a bright green light on the front of a Hyundai Kona EV, and, unsure what it was, I approached it and took this blurry photo:
“Why is this on?” I kept asking myself. “There’s nobody in this car!” I had a lot of questions. “Does this stay on? Does it drain the battery (eventually)? What’s it for?”
As I paced back and forth in front of the car, frantically scribbling my hypotheses into a notebook and listening to the echoes of myself yelling “No, that CAN’T be it! Come on, David, THINK!” I eventually came to my sense. No, I didn’t figure out what the LED was, but I figured out that I was on a Valentine’s Day date with someone who was probably deeply, deeply confused at this point.
I shut my notebook, turned to her while wondering how long I had been caught in that Hyundai LED-induced trance, and offered a questioning smile.
Whew, she understood. Well, she didn’t understand, but she… tolerated it. And so our date went on. I had given her some chocolate from her favorite chocolate spot and a dozen roses, and I was about to take her out for a fancy dinner. Her gift to me? A pair of UGGs (I shit you not; but the short type. I love them) and the greatest Valentine’s Day gift I’ve ever received:
Wait, hold on. I’m realizing I just pasted the version of that photo that one of my colleagues jokingly modified with my photo. Whatever, I’ll keep that there. ANYWAY, the Hyundai’s LED. I did a little digging, and what I found is that it’s called the “Auxiliary Battery Saver.” Here’s what it’s for:
Apparently that green LED turns itself on when the high-voltage battery is charging the 12-volt battery through the DC-DC converter. As a refresher from our “How EVs Work” primer (which is the best explanation of how EVs work on the entire internet), here’s what a DC-DC converter is:
But EVs still have a bunch of low voltage 12V systems, in large part because it’s still cheaper and simpler for car-makers to use off the shelf 12V lighting, wipers, entertainment and other systems that are often shared with their non-EV vehicles. So we need a source of 12V power on board. Step up the next of our unique EV systems – the DC:DC convertor. This is yet another ‘box’, this time – as the same suggests – a piece of power electronics that steps down a DC supply, turning the high-voltage output form the battery, often nominally 400V or 800V, to a (still DC) 12V supply – usually calibrated closer to 14.2V in reality.
A DC-DC converter’s analogy in an ICE vehicle is the alternator – this is the unit that keeps the 12V battery (or batteries in certain EVs) topped up, and the lights and wipers on. If it fails, the failure is similar to blowing an alternator belt on your ‘regular’ car – you have a limited time left before that 12V battery will drain, your lights will start to look like yellow piss-holes in the snow, relays will start to click sadly, and you need to look for a safe place to park up and call the rescue truck. It’s so critical that many EVs will actually have two, redundant, DC:DCs.
In addition, when the climate control has been scheduled prior to the driver entering the car, the light comes on — again, to make it clear that current is flowing from the high-voltage battery:
Why would you need this light? Well, some folks on the messaging boards hypothesize that it’s likely used to notify mechanics that high-voltage is flowing. “Strictly speaking its there to tell service personel that the traction battery is live and being used. it will come on as said every day to check and top up 12v battery,” writes user struthbingham.
I have no clue if this is right; it seems a little subtle to be a significant safety item, and to me seems more like just a notification to make it clear that high voltage is flowing. That said, the Hyundai Ioniq 5 and Kia EV6 also feature an “Aux. Battery Saver” (but on their dashboards), and their user manuals specifically warn against touching the orange wire, so maybe this is a safety thing on some level:
Anyway, there you have it: A car that automatically turns on a Rudolph The Reindeer-esque light on its nose even when the car is off. I’d never seen anything like it before, so I figured I’d share. So the next time you see a Kona with a yellow/green light on its nose, you now know it’s because it’s either charging the battery or preconditioning the cabin with its climate control.
Exciting stuff!
Oh, and the date went great. The dinner was delicious.
It’s a fun gizmo, but why isn’t it red, and under the hood?
This reminds me of the light on F1 cars (and I think some hybrid cars in endurance racing) that tell track workers if a car’s electrical situation is OK and it is safe to approach. Except this Hyundai’s light is the opposite. If it’s on, don’t mess with anything electrical.
I wonder if this is covered in the Rescue Guide for this model. It would also aid first responders to know if the HV current is engaged.
Huh… well that explains that. My wife bought a 2023 Kia Niro EV and she loves it; however, we noticed the amber light on the dash as well. It would come on at random times in the evening in the garage. Our manual was missing from our car, and to be honest I completely forgot to check the internet (that’s embarrassing); however, we called our dealer just to see if they knew what it was, and they had told us it was the car updating their software platform. Soooo I’ll be forwarding this story to them lol.
A dealer making shit up? Say it isn’t so! 😉
Good to know but clearly not isolated. My VX HAS a green led if the alarm is set.