MajorCommonElectrical

Kia EV6: 12V auxiliary battery drain leaving the car dead

12V auxiliary battery drain leaving the car dead is a common electrical fault on the Kia EV6 on the 2021 onward cars, and we rate it major. Putting it right costs $250 to $500 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 10 documented faults on the Kia EV6.

Vehicle: Kia EV6
Years: 2021 onward
Fuel: ev
System: Electrical

This page covers the Kia EV6 as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All Kia EV6 faults10 documented faults on this model

What you are looking at

No photograph available

We do not hold a verified photograph of the 12V battery yet. We would rather show none than show a picture of a different part.

What goes wrong

Separate from (but sometimes related to) the ICCU fault, EV6 owners report the 12V battery going flat overnight even when the main drive battery is well charged, giving a 'check 12V battery' warning and a car that won't unlock or start. Systems staying half-awake — smart chargers waking the car, pre-conditioning, third-party apps — add load. Often it's just a tired 12V battery, but repeat drains can signal the ICCU isn't topping it up, so it's worth distinguishing the two.

What you would notice

'Check 12V battery' warning
Car won't unlock or wake in the morning
Needs the emergency 12V boost function or a jump
Happens after sitting a few days

How to check it

Where to look. 12V auxiliary battery in the boot

Ask if the car has ever been dead in the morning or needed a 12V boost, and how often.
Check the 12V battery age.
Confirm it wakes instantly on approach/unlock.
Frequent drains plus any EV-system warning should push you toward the ICCU questions above.

Parts involved: 12V battery.

What it costs to put right

$250 to $500 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

“Has the 12V battery ever gone flat, and how often?”
“Has the 12V battery been replaced?”
“Do you use any third-party apps or smart-charging that wake the car?”

Now check the Kia EV6 you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in the sources below. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them.

Kia EV Forum EV6 12V battery drain threads (kiaevforums.com)
Recharged 'Kia EV6 Common Problems and Fixes'

Kia EV6 buyer questions

Is 12v auxiliary battery drain leaving the car dead serious on a Kia EV6?

We rate it major and common on the Kia EV6. Separate from (but sometimes related to) the ICCU fault, EV6 owners report the 12V battery going flat overnight even when the main drive battery is well charged, giving a 'check 12V battery' warning and a car that won't unlock or start. Systems staying half-awake — smart chargers waking the car, pre-conditioning, third-party apps — add load. Often it's just a tired 12V battery, but repeat drains can signal the ICCU isn't topping it up, so it's worth distinguishing the two.

How much does it cost to fix on a Kia EV6?

$250 to $500 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which Kia EV6 years are affected?

Our research records this fault on the 2021 onward Kia EV6. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

Ask if the car has ever been dead in the morning or needed a 12V boost, and how often. Check the 12V battery age. Confirm it wakes instantly on approach/unlock. Frequent drains plus any EV-system warning should push you toward the ICCU questions above. Look here: 12V auxiliary battery in the boot