For what it's worth, the battery is compromised when it's brought down to single digit voltages for a while. So until the vehicle is fixed, it's going to blow through 12V batteries. I'd try to insist on a new 12V battery once they are certain the vehicle is repaired, then you've got a good baseline to go off of.

If that fails, and you don't want to fork out the $$$ - charge your current battery up to 100% using a dedicated battery charger. This will get it to a point that should last longer than if the vehicle was charging it.

I make it a point to charge the 12V battery on every vehicle in our family every 4-6 months. It makes them last a lot longer.

 

Excellent advice - thank you. Last time it went in for repair, I pointed out to the dealer that, as the battery is failing within 12 months, and the battery has a 3 year warranty, then every time I get this failure they will be giving me a new battery under the warranty. Personally, I think the battery dying, and the battery sensor going, may well not be a faulty sensor, like they think it is, but that the demise of the sensor is probably a symptom/victim of the real underlying problem - that they need to determine why this keeps happening.

Absolutely agree with your thinking on the battery - my brother, who is an electronics expert, tells me that once a lead acid battery drops below 10V then it's damaged and needs replacing.

 

Absolutely agree with your thinking on the battery - my brother, who is an electronics expert, tells me that once a lead acid battery drops below 10V then it's damaged and needs replacing.

I bought a Ctek MXS 5 in the hope of reconditioning the 12v battery from my 4-year-old Leaf. I started to get weird dashboard warnings/errors and was locked out a few times. I removed the 12v battery from the car and did 2 full recovery charges, it took more than a day to complete. Returned the 12v battery to the Leaf and for around a week the 12v problems disappeared. The random dashboard errors then started to appear again and I was locked out of the car once more.

I bought a new 12v battery and all the problems disappeared permanently. A few months later I visited a friend that I knew had a gizmo that tests car 12v batteries, so took my old Leaf battery along after charging it up again. The result of the test was “Replace”.

 

For info: the battery is a 12V 40AH AGM battery.

AGM? Does it fit in the standard tray? Do you have a link to that exact battery?
I have a 38kwh as well, and I've been looking for an AGM battery for it but can't find a good replacement...

 

Unfortunately, I don't have a link for the battery - the main agent changed the battery for me under the warranty.

 

I looked for a replacement 12v AGM battery for my Ioniq, couldn’t find one the same size with correct terminal posts so just settled on a Yuasa replacement with a 5 year warranty.

 

What model battery was the YUASA? No Hyundai dealership has a genuine battery available and I'm getting mixed messages about it's availability and price. Looking for an alternative but no manufacture seems to be able to match the battery to my vehicle using their site tools. Help!

 

These 2 options may have different sized terminal posts. My '38 wants UK sized posts, these arer larger than the slim Japanese size. Shims are available to convert ...
I buy my replacements from tayna.co.uk, and they show the terminal sizes & layout.
Battery Wizard - Enter Dimensions to find your Battery is their link to find options based on the dimensions.

 

I may have found two options which may work. Neither has the cosmetic lip at the bottom of the existing battery allowing me to keep it held down but I assume there is a solution around that.

Napa BPF151R6
MotoMaster 151r

Question about terminal positioning, forgive me if it's a silly one...but couldn't I just rotate the battery so it aligns with the configuration of the car?

 

There's quite a bit of gadgetry hanging off the 2 terminal posts that I rather doubt the leads would reach. It's night-time now, so a bit too late to look. But here's a top view of mine. Ignore the extra battery at the bottom - my home-brew booster pack. The chunky leads from main 12V go towards the cabin, so I can't see them stretching across each other if you get the mirror-reflection terminal layout, or reaching towards the front of the car if you try rotating it.

 

I have a 38kwh 2020 and had repeated flat 12v battery in lots of different situations. After trying many things as above, it seemed that the cause was the Bluelink connection to my home charger app / API. The app would request the cars battery status many times when plugged in to determine if it should start charging etc. this woke up the car to check and send the data back. Disconnecting my car from the app fixed the issue.

 

Hmm. After more than 40k miles with no issues, mine has now died twice this week. First time was when I went to collect it from the dealers, where it had been sat for a week with 10% battery after the most recent firmware update, after which my charge port actuator died and I couldn’t charge. I assumed this was because the main battery was too low to allow the 12v top up to work. However, after several hours of driving since and 90% in the car it was dead this morning. I suspect the battery is now in poor condition after being drained completely, but the booster pack is now back in the glove box and I’ll leave the trim off the handle so I can get in with the key.

 

This event demonstrates the lack of knowledge that dealers have regarding how the battery system and top up charging works. Clearly if a car is to remain at a dealer for any length of time it is essential to brief them on this and tell them if there is any doubt then they should disconnect the 12V while the car is standing and not being worked on.
To be fair the dealer should be picking up the tab for the failed 12V battery, but I can't see thatr happening.

 

I have a 21 38kwh had a recent issue with 12v battery drain that has led to the battery now ultimately dieing, unfortunately now has fallen out of warrenty, the issue came down the the SOS ecall system draining it as it remained on, dealer is now replacing that under warranty thankfully now but battery seems to need to be replaced as well.

 

The 12V battery in my 2018 BEV has been weak for a while - I even got a portable 12V booster several months ago to keep it going, but it finally kicked the bucket last week - ie would not hold charge over night anymore. Using the booster once in a while to get going is one thing, but to use it to get the car going almost every time I want to drive, is another.

Thanks to the forum I knew what I needed to get - the 151R group battery mentioned elsewhere in this thread - size wise and post location/size, it's an exact match. It's just the little securing lip at the bottom that's missing. I got my replacement battery at NAPA for CAN$112 (similar but more expensive options were also readily available at Canadian Tire, Lordco, etc).

I used a small scrap of wood and some cable ties to secure it, as it doesn't have the little lip on the bottom like the OEM battery does. I don't normally like jerry rigging stuff like that, but I was in a rush and needed my vehicle up and running ASAP, and this was easy at the time. Now I've lost the will to come up with something more elegant. Perhaps my mood will change one day, but that day isn't today.

Pics below if anyone is interested.

 

The 12V battery in my 2018 BEV has been weak for a while - I even got a portable 12V booster several months ago to keep it going, but it finally kicked the bucket last week - ie would not hold charge over night anymore. Using the booster once in a while to get going is one thing, but to use it to get the car going almost every time I want to drive, is another.

Thanks to the forum I knew what I needed to get - the 151R group battery mentioned elsewhere in this thread - size wise and pole location/size, it's an exact match. It's just the little securing lip at the bottom that missing. I got my replacement battery at NAPA for CAN$112 (similar but more expensive options were also readily available at Canadian Tire, Lordco, etc).

I used a small scrap of wood and some cable ties to secure it, as it doesn't have the little lip on the bottom like the OEM battery does. I don't normally like jerry rigging stuff like that, but I was in a rush and needed my vehicle up and running ASAP, and this was easy at the time. Now I've lost the will to come up with something more elegant. Perhaps my mood will change one day, but that day isn't today.

Pics below if anyone is interested.

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Look darn good to me, simple and balanced. If have to replace mine I like this as a solution to the point I would waste the time to look farther.