My Kia EV9's 12-Volt Battery Died For The Third Time In Six Months While We Were 200 Miles From Home, Despite Charging To 100% The Night Before

The transition to electric vehicles has introduced new categories of technical challenges that differ significantly from traditional automotive problems. Among the most frustrating for owners has been the persistent failure of 12-volt auxiliary batteries in electric vehicles, particularly those built on Hyundai Motor Group's E-GMP platform. These failures can leave drivers stranded with fully charged main batteries but completely inoperable vehicles, creating a paradox where the most advanced automotive technology is defeated by conventional 12-volt electrical systems.

Brian Jones's experience with his Kia EV9 represents a particularly egregious example of this ongoing problem, with three 12-volt battery failures in exactly six months of ownership. His latest failure occurred under the worst possible circumstances, demonstrating how these seemingly minor component failures can create major safety concerns and inconveniences for electric vehicle owners who expect reliable transportation from their premium vehicles.

“Well, today was the 3rd time our 12V battery has died in exactly 6 months. Unlike the previous 2 times, the car was locked, and we were 200 miles from home on a Sunday. Drove 200 miles Friday, L2 charged overnight to 100% drove 30 miles on Saturday, and all seemed fine. L2 charge again last night, back to 100% for the return trip. This morning (Sunday) I went out and opened the back, every was fine. Went out 30 minutes later to open the back again and got 2 beeps, no lights or opening. Tried again, one beep. Attempted to unlock with my phone, and nothing. Tried the app and got the 12V battery lower error, so I knew what the issue was.

Thankfully, we were at my parents' house and we had one of the emergency keys. I got the hood open and took a voltage meter to it. 6.84v

I tried the prerequisite booster packs, and the car turned on, but within 30 seconds, the dashboard was flashing like a Christmas tree, and then it died again.

Thankfully, my dad has a 12V battery charger, put it on a 10A charge for about an hour, and it jumped to 11V, which seemed awfully fast. Tried turning the car on again, and the same result came on the light show, then it went black. Obviously, the stock battery was damaged by the first 2 killing despite the dealer telling us it was fine. At the time, I knew I had to play the game, but now I’m beyond pissed. Unfortunately, the only way to ensure we made it home without drama was to put a new battery in it, so I headed to Walmart to buy the cheapest H5 battery I could find. $130 & 20minutes of wrench time, we were on the road.

This issue still plagues the EGMP cars with no real solution. This should easily be fixed at a software level. If I can get a notification every time the car is left unlocked, I should be able to get one when the 12V battery fails to charge the logic and charging attempts stop. Why the hell is it designed to not charge the 12v battery to a full 14.4v whenever it is plugged in to a L2 charger?

We will see what the dealer says and if Kia USA will reimburse me for the Walmart battery. I think I’m going to move to a lithium battery and check the post-tariff prices of the available options. I think I’ll build my own and save a few hundred bucks and end up with a better battery.”

The timing and circumstances of this failure reveal the unpredictable nature of these problems and their potential to create dangerous situations. Despite having charged the main battery to 100% capacity twice in the preceding days, the 12-volt system failed catastrophically within 30 minutes of normal operation. The progression from normal function to complete system failure demonstrates how quickly these problems can escalate, leaving owners stranded without warning in potentially unsafe locations.

Technical Diagnosis Reveals Systematic Problems

Jones's methodical approach to diagnosing the problem in field conditions demonstrates both his technical competence and the severity of the underlying issues affecting EGMP platform vehicles. His voltage measurements and attempted repairs reveal the inadequacy of conventional solutions for addressing batteries that have been damaged by repeated discharge cycles.

Thankfully, we were at my parents' house and we had one of the emergency keys. I got the hood open and took a voltage meter to it. 6.84v I tried the prerequisite booster packs, and the car turned on, but within 30 seconds, the dash was flashing like a Christmas tree, and then it died again. Thankfully, my dad has a 12v battery charge,r put it on a 10a charge for about an hour, and it jumped to 11v, which seemed awfully fast. Tried turning the car on again, and the same result came on the light show, then it went black. Obviously, the stock battery was damaged by the first 2 despite the dealer telling us it was fine.

The measured voltage of 6.84 volts indicates a severely depleted battery that falls well below the minimum threshold required for proper vehicle operation. The failure of multiple recovery attempts, despite temporary success, confirms that the battery had been permanently damaged by previous discharge cycles. The dramatic dashboard warning display and rapid system failure demonstrate how 12-volt battery problems can cascade into multiple system malfunctions that render the vehicle completely inoperable.

The rapid charging behavior observed during the recovery attempt provides additional evidence of internal battery damage that conventional testing methods may not detect. The dealer's previous assessment that the battery was "fine" after earlier failures proved inadequate, highlighting gaps in diagnostic procedures and service quality that leave owners vulnerable to repeated failures.

Community Expertise Fills Service Gaps

The response from experienced EV9 owners reveals a community that has developed sophisticated technical knowledge to address problems that official service channels have failed to resolve adequately. Derek Wolfson's detailed technical recommendation demonstrates the depth of understanding that dedicated owners have developed about optimizing their vehicles' electrical systems.

Just get a nice AGM — lifepo4 is overkill for this application, and the charge curve from the ICCU may overcharge a lithium battery depending on the set points. I'm sure others have figured this out.

Wolfson's advice reflects an advanced understanding of battery chemistry and charging system compatibility that goes beyond basic replacement approaches. His warning about potential overcharging of lithium batteries by the Integrated Charge Control Unit reveals awareness of system integration issues that could create new problems even when attempting to improve reliability through upgraded components. The casual reference to others having "figured this out" indicates an active community of owners who are developing and sharing technical solutions to address manufacturer design shortcomings.

This peer-to-peer knowledge sharing represents both the strength of enthusiast communities and the failure of official support channels to provide adequate guidance for addressing ongoing reliability problems. The fact that owners must develop their own expertise about battery chemistry and charging system compatibility highlights significant gaps in manufacturer support and service training.

Software Issues Compound Hardware Problems

George Fisher's experience with software-related solutions provides crucial insight into the complex interaction between connected car services and 12-volt battery reliability. His detailed account of the diagnostic and repair process reveals how software issues can contribute to hardware failures in ways that are not immediately apparent to service technicians.

Try to change your Kia Connect password. I have had issues since July. Kia finally had the dealer ask me to change my Kia Connect password, and they "reset" the car. Although my user profile and some settings still remained while others had to be set up again. At any rate, it's been a week since I got it back, and I haven't had an issue yet. I was extremely skeptical as the cause from the bulletin shared from Kia wasn't applicable to me as I didn't have any third-party dongle nor third-party accessing/using my Kia connect credentials… I actually have a lemon law case open because it took them 59 days…

Fisher's experience suggests that connected car services may contribute to 12-volt battery drain through continuous communication and monitoring activities that operate even when the vehicle appears to be completely shut down. The dealer's recommendation to change passwords and reset the vehicle's connected services indicates recognition that software and connectivity features may be contributing to the hardware reliability problems, though the underlying mechanisms remain poorly understood.

His skepticism about the solution, combined with the opening of a lemon law case due to extended repair times, demonstrates the serious impact these problems can have on owner satisfaction and vehicle usability. The 59-day repair timeline represents an unacceptable service experience that effectively removes the vehicle from service for nearly two months, justifying legal action and highlighting systematic failures in manufacturer support processes.

The fact that Fisher's case didn't involve third-party dongles or credential sharing eliminates common explanations for connectivity-related battery drain, suggesting that the problems may be inherent to the vehicle's design rather than caused by owner behavior or aftermarket modifications.

EGMP Platform 12V Battery Issues

• The Integrated Charge Control Unit (ICCU) fails to properly maintain 12-volt battery charge levels, leading to premature battery failure and vehicle inoperability despite fully charged main batteries.
• Despite sophisticated monitoring capabilities, the vehicle provides no advance warning of impending 12-volt battery failure, leaving owners stranded without notice in potentially dangerous situations.
• Kia Connect and other telematics services may contribute to excessive 12-volt battery drain through continuous communication and monitoring activities that operate during vehicle shutdown periods.
• Dealer diagnostic procedures and service training appear inadequate for identifying damaged batteries and addressing underlying system problems that cause repeated failures.

Safety Concerns Emerge from Charging System Problems

Michael Iimura's observation about overcharging symptoms during home charging provides alarming evidence of potentially dangerous conditions that extend beyond simple reliability concerns. His detection of physical warning signs during routine charging sessions indicates safety hazards that could affect both battery life and personal safety.

My car has failed to start once in my garage. However, I have since noticed a faint sulfur smell while charging in my garage. This is evidence of over-charging the 12V. I opened the hood and confirmed that the 12V battery was warm to the touch and the terminals were hot. This will certainly shorten the life of the battery, even if the ICCU is "working as intended". I will be reporting this to my service center when I take it in for the first service.

The physical evidence of overcharging that Iimura describes suggests that the charging system problems may be more severe than simple undercharging issues. The combination of excessive heat, sulfur odors, and hot terminals indicates potentially dangerous conditions that could lead to battery failure, fire, or toxic gas exposure. His commitment to reporting these findings to the service center demonstrates responsible ownership practices that could help identify and address broader safety issues.

The observation that these conditions occur even when the ICCU is "working as intended" suggests fundamental design problems that may require engineering changes rather than simple component replacements or software updates. The fact that owners are discovering these safety concerns through their own observations rather than through manufacturer testing or service inspections raises questions about the adequacy of safety validation procedures for these vehicles.

Systematic Solutions Required for Platform-Wide Problems

Jones's frustration with the ongoing nature of these problems reflects broader concerns about the E-GMP platform's fundamental design approach to 12-volt battery management. His technical analysis of potential solutions demonstrates how experienced owners have developed a better understanding of the underlying issues than some service technicians.

This should easily be fixed at a software level. If I can get a notification every time the car is left unlocked, I should be able to get one when the 12V battery fails to charge the logic and charging attempts stop. Why the hell is it designed to not charge the 12v battery to a full 14.4v whenever it is plugged in to a L2 charger?

His analysis identifies specific technical shortcomings in the vehicle's design that contribute to ongoing reliability problems. The observation about notification systems highlights the inconsistency in how the vehicle monitors and reports different system states, suggesting that the technology exists to provide better failure prediction but has not been implemented effectively. The question about charging voltage management points to fundamental design decisions that may contribute to premature battery failure by not maintaining optimal charge levels during extended charging sessions.

The practical solution of purchasing a replacement battery at Walmart demonstrates the immediate priority of ensuring reliable transportation, even when the underlying system problems remain unresolved. 

Unfortunately, the only way to ensure we made it home without drama was to put a new battery in it, so I headed to Walmart to buy the cheapest H5 battery I could find. $130 & 20minutes of wrench time, we were on the road. This pragmatic approach reflects the reality that owners must often take responsibility for resolving problems that should be addressed through warranty service and system design improvements.

Owner Response and Solutions

• Experienced owners have developed technical expertise about battery chemistry, charging systems, and upgrade options that often exceed dealer service capabilities and manufacturer guidance.
• AGM and lithium battery options provide improved reliability, though compatibility with existing charging systems requires careful consideration of ICCU charging curves and voltage settings.
• Password changes and vehicle system resets may address connectivity-related battery drain issues, though effectiveness varies by individual case and underlying causes remain poorly understood.
• Owners have learned to carry replacement batteries, charging equipment, and diagnostic tools to address failures in field conditions when official support is unavailable.

The ongoing nature of 12-volt battery problems in EGMP platform vehicles represents a significant challenge for Hyundai Motor Group's electric vehicle reputation and customer satisfaction. The combination of frequent failures, inadequate dealer support, and the need for owners to develop their own technical solutions creates a poor ownership experience that could discourage broader electric vehicle adoption.

The experiences shared by owners like Jones, Fisher, and Iimura provide valuable feedback for engineering improvements and service process enhancements that could prevent similar problems in future vehicles. However, the persistence of these issues across multiple model years and vehicle types suggests that systematic platform-level changes will be necessary to achieve the reliability standards that customers expect from premium electric vehicles.

The contrast between the sophisticated technology of electric powertrains and the persistent problems with conventional 12-volt systems highlights the complexity of integrating traditional and advanced automotive technologies. Successful resolution of these issues will require comprehensive system engineering approaches that address both hardware and software aspects of vehicle electrical systems, along with improved service training and diagnostic procedures.

As the electric vehicle market continues to mature, the resolution of systematic reliability problems like the EGMP platform 12-volt battery issues will be crucial for maintaining consumer confidence and supporting continued adoption. The ongoing documentation and analysis provided by dedicated owners will continue to be valuable for identifying problems and validating solutions as manufacturers work to improve the reliability and ownership experience of their electric vehicles.

The development of community expertise and aftermarket solutions demonstrates the resilience of dedicated owners, but also highlights the failure of manufacturer support systems to adequately address known problems. The need for owners to invest their own time and money in developing solutions to fundamental design problems represents an unacceptable burden for customers who have purchased premium vehicles with expectations of reliable operation and comprehensive manufacturer support.

Have you experienced 12V battery issues with your electric vehicle? What solutions have you found most effective for preventing or addressing these failures, and do you think manufacturers are doing enough to resolve these systematic reliability problems? Share your experiences with EV reliability and service support in the comments below.

Image Sources: Kia Media Center

Noah Washington is an automotive journalist based in Atlanta, Georgia. He enjoys covering the latest news in the automotive industry and conducting reviews on the latest cars. He has been in the automotive industry since 15 years old and has been featured in prominent automotive news sites. You can reach him on X and LinkedIn for tips and to follow his automotive coverage.