If you’ve splashed out on a shiny new hybrid or electric car expecting it to be the last word in reliability, a chunky new piece of consumer research might give you pause.
It turns out that one of the most basic bits of any car, the little 12-volt battery, is causing a surprising amount of grief for owners of some of the country’s most popular hybrid and electric models. Some brands are seeing failure rates more than ten times higher than petrol cars. Here’s what’s going on, which models are worst affected, and how to keep yourself out of trouble.
Why a tiny battery is causing such big problems
When you think of an electric car or hybrid, the battery that springs to mind is the massive one powering the motors. But every car, no matter how futuristic, also has a smaller 12-volt battery tucked under the bonnet or in the boot. This little battery handles all the basic stuff like locking the doors, turning the lights on, running the infotainment system and starting the car.
In petrol and diesel cars, it’s usually completely unremarkable, plodding along for years without causing any fuss. In a lot of new hybrids and EVs, though, it’s becoming a properly common point of failure, leaving drivers stranded with a car that simply won’t switch on. The frustrating bit is that the rest of the car works fine. The big battery still has plenty of charge, but with the little 12-volt out of action, the car effectively becomes a £40,000 paperweight on the driveway.
Just how bad the problem actually is
A survey of more than 60,000 UK car owners has put hard numbers on the issue. Owners of self-charging hybrid cars less than four years old were four times more likely to have a flat or failed 12-volt battery than owners of pure petrol cars over the same period. Plug-in hybrids and full electric cars were also more than twice as likely to suffer a 12-volt battery failure.
Around 5.5% of hybrid owners reported the problem, compared to 1.4% of petrol owners and 1.8% of diesel owners. EVs sat at 3.8% and plug-in hybrids at 3.5%. Those numbers might not sound like a big deal on paper, but they translate into thousands of UK drivers being caught out by a fault they really shouldn’t be experiencing on a near-new car.
The brands and models hit hardest
Some brands are far worse than others. Hyundai EVs topped the table with a 16% fault rate, followed by Toyota’s full hybrids at over 10% and Lexus full hybrids at just over 9%. Kia EVs weren’t far behind at 7.5%. The really striking figures come when you zoom in on specific models, though. The Lexus LBX clocked a fault rate of just over 29%, while the Hyundai Ioniq 5 came in at 27%, making them around 20 times more likely to suffer a 12-volt battery problem than the average petrol car.
The Toyota Yaris Cross hybrid hit 19%, the Kia EV6 18.8% and the Kia Soul EV the same. The Hyundai Kona Electric and Toyota Yaris also featured high on the list. With the Hyundai Ioniq 5, around half of the owners affected had the fault fixed under a recall, which is good news from a cost point of view but still means the inconvenience is real.
The two different problems behind it all
Interestingly, there isn’t one single fault behind these figures. There seem to be at least two separate issues at play. For Hyundai and its sister brand Kia, the cause appears to be software-related. The car’s systems aren’t keeping the 12-volt battery properly charged, or are quietly draining it while the car is parked. Both brands have issued software updates to address this, and Kia in particular has rolled out an update for the charging unit that helps manage the battery’s charging and temperature.
Owners can check whether their car has any outstanding updates by speaking to a dealer or using the manufacturer’s online service campaign checker. For Toyota and Lexus, the problem looks more like a parts quality issue. The original batteries simply weren’t big enough to keep the cars powered up during longer stretches of inactivity.
The company has since fitted higher-capacity batteries to newer models and is offering battery quality inspections at dealers. If your battery turns out to be from a problem production run, you can get a replacement free of charge.
What real owners are saying
The frustration in the survey responses is genuine. One Toyota Yaris Cross hybrid owner came home from a one-week holiday twice to find her car completely dead. When she contacted Toyota, she was told the fault wasn’t with the battery, but with her leaving the car for a week without driving it. She bought the car in March 2025, and nobody had told her at the point of sale that the car couldn’t be left for a week.
A Hyundai Kona Electric owner had his 12-volt battery fail just over two years into ownership, and was told by Hyundai he’d have to cover the cost of replacement because the warranty had just expired. A Kia EV6 owner had his car stuck at the dealer for six weeks while they tried to diagnose a mystery battery drain.
Another Lexus owner was told by his dealer that doing fewer than 8,000 miles a year was the cause of his problems. None of these are reassuring conversations to be having about a car that was supposed to be near-flawless modern technology.
Will your warranty cover it?
Whether you’ll be out of pocket depends on the brand and the cause. Both Toyota and Hyundai offer a three-year warranty covering 36,000 miles, and Toyota and Lexus hybrids get a longer three-year/60,000-mile policy. If your battery dies inside that window, you should be covered. Of the cars that suffered any sort of 12-volt battery issue from new up to four years old, around 63% of repairs were either covered under warranty or fixed for free under a recall. The other 37% of owners had to cough up themselves.
If your car keeps eating through 12-volt batteries because of a deeper fault that hasn’t been properly fixed, the long-term costs can quickly stack up. That’s why it’s worth pushing hard for a proper diagnosis rather than just paying for one replacement after another. If you feel your dealer isn’t taking the issue seriously, escalate it.
The brands actually getting it right
Not all hybrid and electric brands are struggling with this issue. The same survey found several brands with 12-volt failure rates of less than 2% for cars under four years old. Kia’s full hybrids came in at just 0.4%, Volvo EVs at 0.6%, Renault full hybrids at 0.8% and Hyundai full hybrids at 1%.
Honda full hybrids managed 1.1%, Renault EVs 1.4%, and Skoda EVs 1.5%. So a lot depends on which brand you go with, and even within the same manufacturer, the fuel type makes a difference. Kia’s full hybrids are basically reliable, while their EVs are causing real headaches.
How to keep your own 12-volt battery happy
Whatever car you’ve got, there are a few simple habits that genuinely help. Take your car for a decent drive of at least half an hour every couple of weeks, since that gives the battery a proper chance to recharge from the engine or charging system.
If your car sits on the driveway for long stretches, especially if you’re often away on holiday or only drive at weekends, look into a trickle charger. These low-voltage devices plug in and slowly bring the battery back up to a full charge over a day or two. Decent ones cost between £25 and £200 and most are easy enough to use, but check your car’s manual first as not all cars are compatible.
If you do find yourself with a flat 12-volt and no time to mess about, a jump start from another car or a portable jump pack should get you going. Hybrids and EVs need a bit of care here, though, since some have specific jump-start points that aren’t where you’d expect them, so check the manual or get advice if you’ve never done it before.
What this really means if you’re shopping for a new car
For anyone about to buy a hybrid or electric car, the takeaway isn’t to avoid them entirely. It’s to do your homework on the specific model you’re considering, and to ask the dealer directly whether there are any known 12-volt battery issues and any outstanding software updates. Check whether the model is in the worst-affected list above and ask what the manufacturer is doing about it.
If you’re looking at a Toyota or Lexus hybrid, ask whether the higher-capacity battery has already been fitted to the car you’re considering. If you’re looking at a Hyundai or Kia EV, ask about the latest charging unit software update. And whatever you choose, find out what the warranty actually covers and for how long.
The technology in modern cars is remarkable, but it’s only as good as the smallest, dullest little battery sitting under the bonnet. The companies behind these cars are slowly getting on top of the issue, but until they have, a bit of extra research before you sign on the dotted line could save you a properly annoying experience down the line.
