Mercedes has identified an issue with its battery that is at the heart of its recent Formula 1 race retirements which have cost both George Russell and Kimi Antonelli, and is working on a permanent fix.

After Russell’s Mercedes conked out while he was leading the Canadian Grand Prix last month, Antonelli suffered the same fate while running in second place in the Barcelona GP last weekend. Both were linked to a failure with Mercedes' battery.

While not specifically linked to the works team’s problem, customer squad McLaren has also suffered a run of electrical trouble; Lando Norris needed a battery change during the Monaco GP weekend and retired from the race with power unit settings being noted as the cause of his DNF, while both Norris and Oscar Piastri failed to start the Chinese GP with separate electrical issues.

Speaking immediately after the Barcelona GP, Wolff said Mercedes can’t afford the run of retirements in the battle for the F1 world titles and the team would “leave no stone unturned to understand” what was causing the unreliability.

Kimi Antonelli's Barcelona GP retirement prompts reliability concerns at Mercedes

After diagnosing Antonelli's car after the Barcelona race, Mercedes technical director James Allison said the team has pinpointed the issue to its power unit’s battery and a permanent fix is being worked on.

“I think anyone who's a keen watcher of the sport will have seen that this has laid a few Mercedes engine cars low over the season so far,” Allison said on Mercedes’ Nu Silver Arrows Radio Show. “They're not all identical, but they do sort of originate in the same broad part of the battery.

George Russell, Mercedes

“I think that most of the areas of risk have been understood. And with a bit of luck, when we start to sort of phase in the new modules into the racing season – then our fortunes as a fleet should pick up.

“Obviously for us, that's an important thing. These DNFs are very, very painful.”

Speaking more broadly about how the team designs and builds parts with reliability in mind, Allison explained how the team aims to identify failures either in testing or in engine rigs to avoid being exposed in races – but inevitably, when pushed to extremes and in different racing conditions, previously unidentified weaknesses can appear.

“You accept that there will be failure. We try to make sure that failure happens in testing or on rigs and that it happens as little as possible when you're out there trying to earn championship points,” Allison said.

“Now, clearly it doesn't always work because occasionally the car will DNF and that is definitely a failure of our process and all of our attempts to deliver performance without the downside of that performance.

“But when a failure like that does happen, then in the first instance and perhaps before it's fully understood, then the team will tend to take a slight half-step backwards to be more cautious with the equipment, to push it slightly less hard, just to give a little bit of resilience to the kit that's obviously suffering.

James Allison, Mercedes

“But a different part of the team will try to figure out what was the root cause of that failure to design that out, prove that out and put something back on the table that is sufficiently robust.

“So you do a first intervention that is just to try to sort of give the vulnerable thing an easier life while then working on a proper cure that lets you really cane it.”

Mercedes hasn’t given a timeline on when the “proper cure” will be ready as it begins preparations for four race weekends across five weeks, starting with the Austrian GP next weekend.

But given its two DNFs in Canada and Barcelona have effectively cost 43 points - ignoring changes of positions for the sister car after the retirements - Mercedes' dominant position in the F1 world constructors' championship has been eroded to 72 points by Ferrari.

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Mercedes had a poor weekend at the Barcelona Grand Prix overall, given their status as the season’s strong favorites.

The Barcelona track was formerly the testing ground for the preseason due to its having characteristics of many different kinds of tracks.

With Barcelona coming a decent chunk into the season, it is now a track where teams bring big upgrades and look to fully realize their benchmark.

Despite Mercedes taking pole position, they ended up falling well short of a victory, losing to Ferrari by 19.5 seconds, and Kimi Antonelli suffered a reliability issue that cost him.

The car has certainly been bolstered by its class-leading power unit, which has given it a significant advantage in natural lap time.

However, Barcelona has exposed the car’s lack of speed in aerodynamic performance.

“The W17 is clearly a good car, not just a mediocre one elevated by a mega power unit. There was already more than a hint of its impressive downforce in Monaco, where Kimi Antonelli blitzed the opposition on a track that obviously isn’t power sensitive,” F1 reporter Scott Mitchell-Malm wrote for The Race.

“Putting three-tenths of a second on customer McLaren at a proper aero track like Barcelona showed the car’s one-lap potency. 

“Mercedes’ bid to win faded when early race leader George Russell started struggling in the second and third stints, though. Its faster driver Kimi Antonelli was happier with the pace of the car, so this was a silver lining – but he retired late on with yet another Mercedes technical problem. 

“Russell called it ‘a big concern,’ and the lack of pace he had on the hard compound gives Mercedes homework to do on the car side, too.”

With Ferrari making notable gains in car development, McLaren likely continuing to push, and Red Bull increasing their desperation, Mercedes cannot afford to sit on their hands.

\This past weekend’s developments highlight the need for a serious upgrade package.