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Compact Dynamics was able to breathe a sigh of relief after the Monte Carlo Rally. Rally1 cars had made their debuts and there hadn’t been a single hybrid failure that had forced any of the World Rally Championship’s elite drivers to park up and retire.

There was the odd blip, where multiple drivers remarked they had not been able to utilize the hybrid boost on a stage occasionally. But that was it. Not bad for a new hybrid system plumbed into brand new cars.

But potentially its biggest challenge of the year is coming from Rally Sweden. Batteries do not function well in extreme temperatures, both in terms of capacity and power delivery, and this week presents the coldest temperatures the WRC is likely to experience all year.

Monte had a little snow and ice here and there. But nothing like Sweden.

“We have started here [in Monte], where the climatic conditions are quite good, but we are going to Sweden; it’s cold,” Compact Dynamics’ chief Oliver Bamberger tells DirtFish.

Calling Sweden cold sounds like a understatement on paper but it might not be – at the time of writing, temperatures during the rally are forecasted to nudge slightly above freezing point.

Such mild conditions will be helpful for the hybrid tech, at least. Chemistry is a fickle business; how compounds interact with one another affects the efficacy of electric motors and those interactions are not always consistent when temperatures fluctuate.

Aside from the temperatures, there’s another challenge facing the drivers – regenerating enough battery power under braking to deliver boost.

That has both upsides and downsides. On icy roads an extra kick up the backside of unexpected power could have unfortunate consequences – and there are lots of junctions on this rally where managing corner exit traction will be tricky.

But drivers could also find themselves lagging behind if they’ve not been able to regenerate as much power for hybrid boost under braking as their rivals. There are lots of long straights with an absence of braking zones in Umeå, the new host region for Rally Sweden. That poses a challenge.

“For sure, some stages, or many stages, will have a lot less boost anyway deploying also because we always need to regenerate it,” explains Toyota’s Kalle Rovanperä.

“Many of the fast sections where you don’t do proper braking, just maybe left-foot braking and small braking in the fast corners, of course we will have less boost in those areas.”

To a certain extent, it’s the same for everyone. All the drivers will compete on the same stretches of road. But as M-Sport’s Adrien Fourmaux elucidates, sacrificing a little bit of speed in the braking zones could pay them back on the way out.

“The only solution you can have is to try and get really efficient braking. If you lock up the tires, then you don’t regen,” said Fourmaux. “So you have to have quite clean braking and maybe try to brake a little bit earlier for a little bit longer. But that’s the only thing you can do.”

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