I would remind people that they don’t really need to worry about their electric car batteries.
The vast majority of batteries survive until the vehicle is crashed, mechanically destroyed, or traveled more than 300,000 miles. There is a small subset that either has insufficient cooling or poor battery management and deteriorates at that point. A few of them suffer from manufacturing defects, which always require replacement under warranty.
The Hyundai Ioniq 5 files in that last category. A small subset of Early production 2025 Ioniq 5s– First models built in North America, with North American Charging System (NACS) plugs – “You may experience a charging problem where the voltage difference between the battery cells prevents the high-voltage battery from fully charging,” states a technical service bulletin filed with the National Highway Traffic Administration.
Solution: Replace the battery. But if you want to see what it’s like to experience increased battery voltage, watch the video below from Ionic Man. Founder Corbin runs one of the best channels for Hyundai issues, in part because he’s currently using his third Ioniq, and his second an Ioniq 5.
On a recent road trip while on vacation, my 2025 Ioniq 5 stopped reaching its peak charging rate, and struggled to maintain its charging curve. Corbyn pointed this out immediately. He is, after all, the kind of electric car nerd (like me) who follows his charging curve on various devices to track the car’s performance. What he saw was alarming, and he continued to a variety of different charging stations.
The charging speed continued to slow until finally the car could not fast charge at all. Level 2 charging worked until the battery eventually died.
And knowing what we do about the potential difference, this path. Electric vehicle battery packs consist of hundreds of cells, and must be charged and discharged evenly. Battery packs are unstable when the cells are out of balance, which can lead to dangerous conditions, so the car’s Battery Management System (BMS) monitors the cell voltage and keeps everything charged evenly. But when the BMS logic fails or when the cell has trouble charging or discharging, this voltage difference will initially slow down the maximum charging speed until the fault grows, at which point the car will trigger an error code and shut itself down.
Corbin’s vehicle generated fault code P1AA700 – a generic troubleshooting code that can be read by an OBD2 code reader – for cell voltage deviation. Hyundai quickly recognized this as a clear sign of voltage failure and ordered a replacement battery for the Ioniq 5. (He also had a great explainer video of the P1AA700 issue before his personal experience.)
In an email to InsideEVs, Corbin confirmed that the company had fast-tracked the battery. But the coolant refill process may not have been performed properly, resulting in a low coolant issue shortly after you received the vehicle. He’ll have a full update on the saga sometime soon.
It’s definitely a frustrating experience. But understanding the mechanisms of battery failure also helps demystify this technology. This is not rocket science. The cell must charge and discharge reliably and at a predictable rate. The BMS must monitor and rebalance charge imbalances. The cooling system must maintain the system at a safe and efficient temperature. As long as these components are doing their job, batteries can easily last for hundreds of thousands of miles.
But here’s the best part: They’re all also guaranteed for eight years or 100,000 miles. Any production quality issue with the battery cells or BMS logic fault is likely to arise within the first 100,000 miles of a vehicle’s life, so most failures will result in warranty replacement. Modern electric car batteries don’t break down very often.
The point is: you really shouldn’t worry about it.
Contact the author: Mack.Hogan@insideevs.com.
