I'm still gathering info for the Tucson HEV and PHEV specifically but based on what I have found, Hyundai moved to incorporate the 12V battery into the higher voltage traction battery several years ago. Instead of separate batteries, they is only 1 and it is 'partitioned' to have the required capacity of both voltages. The battery reset switch 'jump starts' the 12v if that is needed.This is definitely true for my Tucson HEV.

I would expect them to use the same approach for the PHEV, a single battery for traction and 12v, but I haven't been able to confirm that yet.

This article explains what they have been doing fairly well across their line of hybrids:

How the Hyundai Ioniq Ditched Its Traditional 12V Lead-Acid Starter Battery

It's deceptively simple—if it needs a jump-start, this hybrid provides its own. Read more and see pictures at Car and Driver.

www.caranddriver.com

 

Thanks for the reply and information!

 

Looks like under the cargo area

 

Is that the spare tire area of a PHEV Tucson? cheers, roger

 

yep, looks like for the PHEV they split the batteries and stuck a low voltage battery (yellow) in the spare tire area under the cargo floor. Bad news for carrying a real spare tire.

HYUNDAI TUCSON PHEV SUV, 5 doors User Guide

Learn how to safely operate the HYUNDAI TUCSON PHEV SUV, 5 doors with this comprehensive user manual. From airbags to high voltage components, this guide covers it all. Keep your vehicle stable and completely immobilized with step-by-step instructions. Access the battery with ease and disable...

manuals.plus

 

That has got to be the goofiest BS I've seen in a long time... All that stored electric energy and they they still put a 12V battery in the trunk? Lol/....

 

The Ioniq and Niro were the first cars to incorporate the 12-v battery in the traction battery case and make the battery lithium-ion saving 25lbs in the process. It was a fairly strong selling point. Strangely, this was only featured in the NA versions of those cars. The European Ioniq and Niro kept the conventional pb-acid battery. I have no idea why the difference in the NA approach and world approach to powering the 12-v bus.

 

The Hyundai Canada factory warranty only provides 24 month, 40,000 km coverage for the 12 volt battery and it’s excluded from both the extended hybrid warranty and Premium Plus Extended Warranty.

This might make sense with a normal (cheaper) 12v battery in the non-Hybrid models, but sounds like it’s going to cost a lot to replace. Does anyone know what a replacement costs; I’m guessing a lot.

 

About $900.00 including labour. It’s a lithium ion battery.

 

I am confused on how to jump start the vehcile if the restart switch does not work. Where do the jumper cables go? Manual states it can be jump starrted but it cannot be used to jump start another vehicle.

Have you set up the vehicle on myhyundai, amazing capabilities on the website and bluelink

 

If you remove the under-hood fuse/relay box cover you'll see a couple posts that you can clamp the + cable to. Both posts are tied together electrically. You can pick up ground any convenient place nearby the box.

One thing to be mindful of is that "normal" jumper cables are heavy because 100+ amp load of the starter motor. In the hybrid's case, we're not starting the car with the jumpers. We're only powering the 12-V bus. I would not carry jumpers bigger than 14 ga. Smallish motorcycle battery clamps should be plenty big enough on the ends of the cable. In fact, a motorcycle jumper cable with small clamps on one end and a cigarette lighter plug on the other would be the thing to carry.

 

The online manual (9-27/28) for our 2022 Tucson Hybrid PHEV purchased in Canada refers to a 12v AGM MAT battery so I’m puzzled what we actually have. I also wonder how the 12v battery gets charged. Does it require the engine running to recharge? Or does it draw from the Hybrid battery. Does anyone know?

 

I have same question regarding 12v charging. Called two different dealers (in US) and got opposite answers: one said from alternator and one said from hybrid battery. I left 2022/Tucson PHEV (3000 miles) in home garage for 3 weeks and when I came home it was dead. Finally got gas engine started with a jump and noted hybrid battery fully charged. No way to check 12 volt charge. ?’s: If 12v is charged by hybrid battery, why was 12v dead? Bad relay between the two? Is the 4 month old 12v defective? What caused 12v to discharge? As best I can tell, everything was off in car when I left and keys well away from vehicle. Is Bluelink always on and discharging 12v battery? Glad I hadn’t driven it to airport. Hyundai, somebody….need some accurate info here.

 

No, it’s supposed to be there for storage of items.

 

Thanks, but the reason I queried it is that the place to stow the cargo cover is blocked by the foam insert. It doesn't make sense that you can have one but not the other!

 

Interesting to note that when the HEV Tucson is running, the 12 volt battery voltage varies from 12.5 volts to almost 14 volts depending on the load which would indicate that the DC to DC converter is doing it’s job in maintaining the 12 volt battery. When in Accessory mode, you get the annoying beep and message indicating to turn the vehicle on to prevent battery depletion. I have played the stereo in accessory mode for an hour but when the voltage goes down to 12.6 volts, I turn everything off or start the car.

 

I don't use accessory mode. I just leave it in the on position. That way you can leave the hvac on. The engine will start when it needs to.

 

Good question. I've never had that happen to me so I can't answer.

 

I can say with authority that when the 12v battery went dead on my PHEV, NOTHING was going to happen. No lights came on when I opened the door, no seat movement, no chime and pushing the START button had no effect. One guy I called for a jump hooked up a meter on the positive post in the fuse box in front of the driver (under the hood) and somewhere under there I didn't see. He said the battery was dead and "thought" it was okay to jump it there. Since he wasn't sure, I called another guy and it was jumped via the 12v battery under the storage area. Precisely where connections were made, I didn't see. To repeat Sailormann's question, why did the 12v go dead with the lithium battery fully charged? No lights, radios or anything I can control was on and the car was unplugged sitting in my garage for about 3 weeks. Is the 12v battery a dud that won't hold a charge? Is there a bad relay between the lithium and 12 batteries? Even is something was drawing 12v power, the big battery should have maintained the 12v's charge, right? WHen the car started, the lithium indicated totally full.

 

The 12-v battery on the PHEV (pb-acid) can be jumped either location. As explained earlier, the charge on the lithium battery makes no difference when the car is in "off" mode or "acc" mode. The DC/DC converter will not keep up the charge on the 12-v battery when the car is off. You could have a parasitic draw on the 12-v battery that took it down. Or the 12-v battery could be faulty. Both conditions are easy to test.

Maybe nothing is wrong with anything and 3 weeks is the upper limit of standby duty for the 12-v battery.

 

Thanks for the good reply. All possibilities seem like, well, possibilities. As to a parasitic draw, that seems a poor design, if it's intentional. Such a parasitic draw, maybe parked at a northern airport in the winter? Bad news on one's return home. Faulty battery? I'll definitely check that one. Three week limit on the standby battery? Seems pretty short, but one never knows. J - Take no offense! Really, I'm just grumbling at Hyundai our loud. Not you for sure. I'm quite appreciative of your posts. Now, would it make sense to leave the 12v hooked up to a trickle charger? It wouldn't make sense to leave it ON, would it? Maybe I'll just be prepared to have to jump it after a long time away. THANKS again!

 

By parasitic draw, I mean a higher than normal current draw when the car is shut off. There's a spec for it (I think I saw 50mA in one of the service manuals) and the draw can be measured to see if there is some fault causing a higher draw. A trickle charger would temporarily work around a high parasitic load but it doesn't solve the root problem (if there is a problem). Measuring parasitic draw is not hard to do and there are plenty of utube videos on the subject. You could ask a dealer to do it for you.

 

I hope someone is able to get a clear answer from Hyundai on what’s going on and what function the Aux Battery+ function is supposed to have to prevent the 12v battery from running down. Leaving a car for a couple of weeks on vacation isn’t a rare occurrence.

On the HEV they designed a switch so the HEV battery will stand in to start the car. Why wouldn’t the PHEV have the same. I presume it is because of the Aux Battery+ function. However, they made some changes to the Aux Battery+ function in recent updates; what’s in the manual no longer makes sense.

 

I hope someone is able to get a clear answer from Hyundai on what’s going on and what function the Aux Battery+ function is supposed to have to prevent the 12v battery from running down. Leaving a car for a couple of weeks on vacation isn’t a rare occurrence.

On the HEV they designed a switch so the HEV battery will stand in to start the car. Why wouldn’t the PHEV have the same. I presume it is because of the Aux Battery+ function. However, they made some changes to the Aux Battery+ function in recent updates; what’s in the manual no longer makes sense.

I have spoken with a customer service person at Hyundai HQ and she is supposed to be setting me up for "a diagnostic" at one of the larger Hyundai dealers in eastern NC. I'll gladly report whatever they tell me...when they say it. Haven't been able to "fit me in" yet. Right. And, what are some things in a car that are parasitic draws when the vehicle is supposedly totally shut down? As shutdown as is can be in normal operation.

 

I don't think the button connects the traction battery at all, just switches the 12v one back on for 15 secs to allow you to switch on the ignition.

 

mərhəba After the 2021 santafe yacht was finished, they tried to fight and after we put fuel, we said the 12 volt battery is dead (P1B9600) HIGH VOLTAGE BATTERY CELL gives the VOLTAGE DEVİATION fault, why the vehicle does not start?

 

Ok from Europe, had the same problem with the 12v battery.Last month i went with the car to do the 15000km service at Hyundai.All when and good ultil they tested the 12v, 30% charged.They ask my how much did i drived in electric mode.I had at that moment 12000km, 9000 of them on electric mode only.They said that the 12v only charges when the ICE is on.Told me to come next week to do a full charge of the 12v bat.That week i had only driven in sport mode, got the fuel consumtion a little up.Went to them again battery charge from 30% to 80%.From then on i usually take the car once a week to do 30km on the highway, just to keep the 12b bat charge.
Sorry for the multitudine of misspells

 

This is a new wrinkle; we really need clarity from Hyundai on this. Owners need to know how to maintain their 12v start battery especially now it is colder. The Aux Battery+ function unique to the PHEV is designed to keep the 12v battery charged. It’s not clear what role the ICE plays but doubt it’s as simple as using it to keep your battery charged. Hoping others have info on this.

 

I came across this video from Hyundai for the IONIQ describing the Aux Battery + function. Have to assume this is how it is supposed to work with other PHEV’s like the Tucson. Maybe we need a video describing the feature for our Tucson PHEV’S to clear up how this works or doesn’t work.

 

Can confirm that when my Tucson PHEV stayed three weeks parked the 12V battery was completly dead, had to open the car with the physical key hidden on the electronic key.

The only way to bring the car back to life is by jump start using the + 12V connector inside the under the hood fuse / relay box. DO NOT JUMP START CONNECTING DIRECTLY TO THE 12V BATTERY ON THE TRUNK / LUGGAGE COMPARTMENT.

After you bring the car back to life, drive for at least 30 miles, and if possible, force the ICE to start, will help the DC/DC converter to recharge the 12V battery back to it's optimum charge level.

ONLY IF NEEDED disconnect the 12V battery from the car to recharge it using an external charger.