Battery issue...?

D

Daniel Delaon

New Member
Back in October, I strted getting these "12v battery discharging due to additional electrical devices" messages, and then the (original parts) 12v battery died and stopped being able to keep a charge. So I checked with the dealer and they said the battery was my responsibility (fair enough). I replaced it with a store brand here in France (Norauto).
Two weeks later the Norauto battery died. I took it into the dealer who said there is nothing wrong with the car and charged the battery for me.

When it died again, they said it was a bad battery (making derogatory noises about non-original parts) and I needed to have an original 12v battery. I started disconnecting the battery at night, and about a week later I bit the bullet, figuring that if I had a bad battery, a new one would solve the problem, and if the problem continued the dealer would actually investigate the issue. (silly me.)

So the new, 10 day old orginal parts 12v battery died Saturday night during the night, and I had to recharge this new battery.

I called the dealer to set up an apointment, but I was fobbed off with the claim that I am not driving the car enough for the 12v to get recharged while driving.

I am in year 3 of leasing a Niro electric. The lease is tight, 10k km/6,200mi per year with a 10% allowance. So right now I should be under 33,000km and I'm at 38,000km. As a result, I have been driving this car less than our other car, a hybrid Honda from 2010. Between the begining of November and 10 January, I drove about 1000km, disconnecting the 12v battery at night every night.

As you might imagine, I'm annoyed both about the car and the dealer. I like this car and I want to take care of it. But I also don't want to pay a penalty for my lease.

So... I could use some advice. Can anyone of you learned people tell me
1) Why my 12v battery would discharge enough at night to die?
2) How driving it more would solve the problem?
3) Is there some documentation of this?
4) Why this would battery issue start almost exactly 3 years into the life of the car?

Thank you for any words of wisdom you might have!
Daniel
 
I'm no electrical expert, just curious whether any of your aftermarket parts are electrical and attached to the car's wiring/bus/fuses. Sounds like something's draining it.
 
Thanks for your reply.
I haven't installed any after market parts. I have only replaced the 12v battery. The car is in orginal condition.
Daniel
 
I'm sure you have checked it already but something like the dome light left on is enough to drain the battery in very short order. I would go through all of the lights that are select-able, check to make sure all of the doors are closed tightly (and that the car recognizes them as closed), unplug any/all 12v devices in cigarette lighter plugs and if you have one disconnect any OBD tester.

I had a OBD plug that promised it would shut off after a few minutes of inactivity stay active overnight. That is the one time I have had 12v battery issues on my '22. If you leave a door open while getting groceries out, that can be long enough to put a hurtin' on the 12v battery as well.

I have left my car at the airport for a week long trip without issues so something is definitely draining your battery!
 
Thanks James,
Yep, did all that before coming here.
I was in the US for 6 weeks in summer 2023 and left the Niro unused the whole time. No iussues. I was likewise in the US for 2 weeks last summer and left the Niro unused. Also no issues.
This started in the Autumn of 2024 with the "additional electrical devices connected" warning. (I'm pretty sure that warning is generic; coming on only when the battery goes down to 12v or less.)
So I'm wondering really...
- why doesn't the car recharge the battery?
- why does it drain so much at night? (It dropped from 14.6 at a full charge to 12.3v over two nights, and one of those nights the car was plugged in.)
Anyone know?

Thanks!
Daniel
 
Daniel Delaon said:
So I'm wondering really...
- why doesn't the car recharge the battery?
- why does it drain so much at night? (It dropped from 14.6 at a full charge to 12.3v over two nights, and one of those nights the car was plugged in.)
Anyone know?
Click to expand...
No mention of model year but assuming a gen-1 Niro my understanding of this model is that it charges the 12V battery once a day while parked, unlike the Kona's 6 times for the first 56 hours only. It's a puzzle as to why Kia deviated in this single detail.

I know from BM2 voltage logs on my (electrically-similar) MY2019 Kona 64kWh that when the rate drops from 6 times to once a day the 12V battery does not stay fully charged for long. It's adequate to start the car but not at 100%.

I don't have Hyundai telematics or any accessories running 24/7 nor have never had a 12V battery problem in the 6 years I've owned this car.

Another detail I've found is that leaving an unpowered charged plugged in will cause the 12V charging schedule to fail, as will of course leaving a door, hatch or the hood open. I menton that because some EV charging programs that control the charging times in return for a lowered billing rate might do that in a way that appears to be an unpowered EVSE as far as the car is concerned.
 
The battery should draw/charge from the traction batteries if it goes low. If this is not occurring and your battery is dying and can then be manually re-charged then: The box that charges the 12V battery from the traction battery is obviously not coming on. This is not theory this is fact. Take it back to the mechanic and tell him to fix it. The battery should *never* just drain to zero. This was a problem with old firmware on vehicles that were not driven enough, but I'd take a 50/50 you are just pulling from your 12V battery 100% of the time.

I will say this, a battery can go bad and still show good, ie it will fall over under anything more than a minimal load, but looks fine to the sensor. However, you've replaced it twice, and if it can be re-charged manually then if overnight the voltage is dropping the sensor should detect it and turn on the charger.

Before you charge it again, I'd like to know what the voltage is immediately after you turn the vehicle off.

Disconnect the 12V manually charge it.
Measure the voltage after 1 hour of rest. This should be your baseline
Connect it to the vehicle, measure it again, This should be your idle nominal
Measure your voltage after driving around for the day. It should be close to nominal.

As long as your traction batteries are charged it should be impossible for a vampire drain to kill the 12V battery.
 
Thank you very much Keith and KiwiME.

Keith, I like to follow the maxim that says something like, never attribute to evil that which more likely to be stupidity. My guess is they are blowing smoke because they don't rightly know what's wrong withthe car. The adoption of electric vehicles has been exceedly rapid here in northern France. I imagine the technicians are farther behind the designers and manufacturers than usual.

I drive very little even by small town French standards. Work is 2km away, kids go to school 2 and 5km away. So the longest commute is a 12km loop on the way out, then 2km home. I have been thinking that I was driving on the 12v, despite all the fun graphic and statisicial information avail as driver distration material on the dashboard screens.

I have been measuing the voltage after use.
When fully charged, the battery read 14.6v
After a weekend, one evening plugged in to charge the traction battery, 12.4v
After driving the next day, 12.3v
Received a message in the car that said additional electrical items were discharging the battery, measured the battery when I got home... 12.4 volts. That one surprised me. I thought it would be under 12.
I'll be more systematic this week.

One last piece of info... I usually drive in Eco mode, just out of habit. This week I have changed the habot to drive in Normal, and sometimes in Sport mode. I was curious to see if that would change anything. No results yet.

Thank you again for the infrormation.
Daniel
 
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RE: Smoke, I agree with you, the mechanic is clueless, and read something somewhere. Was outside yesterday, installing a trailer wiring harness on my NiroEV, (yea I know, not rated), and the amber lamp popped on the KonaEV's front grille indicating it was charging the 12v from the traction batteries. I wish the Niro had this feature, I think it's a good one. I just had a 12v battery failure in the Kona 2 weeks ago, Arizona is brutal on lead-acid batteries. Hit the power button dome light goes out, ie battery literally falls over engaging some relays and starting some electronics, it was 5 years old, my bad not replacing it. But I had noticed it seemed to stay on a lot more, ie on and off thru the night. Since the GF has been out of work, the car tends to not get driven but once a week-ish. The car should be tracking all of this activity, a full diagnostic on these things takes like 6 hours or something, but to your point, they are still working out what to look for.
 
Hi Keith, my version of the Niro (MY 2021) has a feature where the traction battery charges the 12v, but I have only seen it happen one time. I had to look it up in the manual when a single charging light started blinking.

I have an appointment with the dealer for Friday afternoon. If I can get enough voltage measurements, they may have enough info to feel comfortable about doing something concrete, like replacing the charging box.
 
Daniel Delaon said:
I have been measuring the voltage after use.
When fully charged, the battery read 14.6v
After a weekend, one evening plugged in to charge the traction battery, 12.4v
After driving the next day, 12.3v
Click to expand...
Those look normal but really the only way to properly characterise charging of the 12V battery is to use a voltage logger that records without disturbing the car. The most practical tool by far is the BM2 Battery Monitor which you can buy from Amazon at a very reasonable price.

But, based on your added description of use it's pretty clear to me what's probably happened. Everytime you start the car and stop it the 12V battery suffers a small to moderate loss of charge. The longer doors are open when loading and unloading the more that is. After stopping and closing the last door the car takes some minutes to reduce the 12V load to a 'standby' level. Promptly entering Ready mode when starting a trip and delaying turning the car off on arrival will help.

Along with repeated short trips being the problem, that will be aggravated by doors being open for longer periods than absolutely necessary outside of Ready mode. The 12V battery really only gets a once per day 20-min charge and that is quickly spent. While driving only minimal charging takes place.

One solution is to enter Utility mode directly from Ready mode when returning home. A quarter to half hour later just press the Start button to turn it off. In Utility mode the car is secured from being driven off and the 12V battery is being charged for that duration. Hope that's helpful!

BM2 unit 2.webp
 
I have been looking for Utility mode in hte settings, but I can't find it.

Battery monitr: I had no ida ea that such a thing existed! I'm getting one tomorrow!

Thanks!
Daniel
 
HI Folks,
I let the dealer take the car early last Friday. They had it for the weekend and discovered that the switch the releases the latch on the rear hatch/door was malfunctioning. They have replaced it. I have the car again. I'll be tracking any weirdness.
Hopefully this is the fix. :)
Thanks for all your input it was at a minimum helpful at at most valuable ammunition in my convedrsations with the technicians.
Best,
Daniel
 
Hello again everyone,
I wanted to write one last time to say thank you very much for your input and information. It allowed me to go the dealer well armed. They took the car back and investigated in detail all electrical functions.
Guess what... They found a fault with the switch that opens and closes the rear hatch/boot/coffre. Even though it was functioning physically as expected, it was broken and draining the battery. Part replaced, problem solved.
whew. That only took 4 months, 3 visits, one shouting match, and your help to solve it. ;)
Thanks again!
Daniel
 
That's been reported perhaps twice before on the Kona so it's really quite rare, assuming it's the same mechanism. Thanks for reporting back to hopefully close the issue.
 
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