The second half of a historic round-the-world flight, the first ever in an aircraft powered only by solar energy, has been postponed to April 2016, the Switzerland-based team announced on Wednesday.

In a statement, the team of Solar Impulse said that they had been unable to repair the batteries which overheated in the record-breaking oceanic flight from Japan to Hawaii, part of a pan-continental journey which included a stop at the city of Mandalay en route.

“Following the longest and most difficult leg of the round-the-world journey, which lasted five days and five nights (117 hours and 52 minutes), Solar Impulse will undergo maintenance repairs on the batteries due to damages brought about by overheating,” a press statement read.

The hiccup means that the US$40 million project, which was years in the making, must be suspended until the spring of 2016.

[related]

Crowds turned out when the Solar Impulse 2 landed in Mandalay in March – after the fourth flight of its 35,000-kilometre trip around the globe.

The plane is only as heavy a family car (2,300 kg, 5,100 pounds) and but has a wingspan as wide as the largest passenger airliner.

Swiss pilots Bertrand Piccard and André Borschberg say they have undertaken the quest as a medium to show the world the potential of renewable energy.