Washington (AFP) - The sun-powered Solar Impulse 2 aircraft has been grounded in Hawaii, its crew said Saturday, after a grueling five-day, fuel-less flight across the Pacific Ocean overheated its batteries.

The airplane took 118 hours to cross from Japan to Hawaii in the most perilous leg of its goal to circumnavigate the globe without a drop of fuel.

The flight last week saw Swiss pilot Andre Borschberg smash a record for the longest solo plane flight. But the historic journey also took its toll on the aircraft's batteries, grounding it for repairs until at least August.

Too much insulation caused the plane's battery temperature to spike on the first day of the flight and there was no way to cool it after Solar Impulse was off the ground, the aircraft's team said.

"The damage to certain parts of the batteries is irreversible and will require repairs and replacements that will take several weeks to work through," the Solar Impulse crew said.

"Solar Impulse does not see the possibility for any flights before 2-3 weeks at the earliest."

The crew said it's looking for ways to improve cooling as it gets ready to tackle the last five stretches of the 13-leg journey.

Solar Impulse 2 took off from the United Arab Emirates earlier this year in its around-the-world journey powered by 17,000 solar cells and on-board rechargeable lithium batteries, allowing it to fly through the night.

Its wingspan is longer than a jumbo jet but its light construction keeps its weight to about as much as a car.