Peter Lobner
In my 10 March 2015 post, I provided basic information of the remarkable Solar Impulse 2 aircraft and its mission to be the first aircraft to fly around the world on solar power. On 10 July 2015, I posted a summary of the first eight legs of the around the world flight, which started in Abu Dhabi on 9 March 2015 and ended on 3 July at Kalaeloa, a small airport outside Honolulu, Hawaii.
After arriving in Hawaii, the Solar Impulse team determined that the batteries had been damaged due to overheating on the first day of the Leg 8 flight and would have to be replaced. Solar Impulse reported the following root cause for the overheating:
“Since the plane had been exposed to harsh weather conditions from Nanjing to Nagoya, we decided to do a test flight before leaving for Hawaii. Having to perform a test flight followed by a mission flight had not been taken into account in the design process of the battery system, which did not allow the batteries to cool down in between the two” (flights).
By November 2015, the Solar Impulse engineers had upgraded the design of the whole battery system and integrated a battery cooling system. You can read the details on the Solar Impulse website at the following link:
http://blog.solarimpulse.com/post/133346944960/cool-batteries-solarimpulse
A further delay in starting Leg 9 was caused by the seasonal shortening of daylight hours in the Northern hemisphere. The late autumn and winter daylight hours weren’t long enough to allow the batteries to be fully recharged during the day along the planned route to the U.S. mainland and back to Abu Dhabi.
Source: Solar Impulse
On 26 February 2016, the upgraded Solar Impulse II made a successful “maintenance” flight in Hawaii. The flight lasted 93 minutes, reached an altitude of 8,000 feet (2,400 meters), and included tests of the stabilization and battery cooling systems.
Solar Impulse is planning to restart its around-the-world journey on 20 April 2016.
Source: Solar Impulse
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