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Solar Impulse 2, a fully electric plane, has landed in California after its team spent months fixing a problem with overheated batteries:
An experimental plane flying around the world without a single drop of fuel landed in California after a two-and-a-half day flight across the Pacific. Piloted by Swiss explorer and psychiatrist Bertrand Piccard, Solar Impulse 2 touched down in Mountain View just before midnight (3 a.m. ET). "It's a new era. It's not science fiction. It's today," Piccard told CNN from California after his successful voyage. "It exists and clean technologies can do the impossible."
While Borschberg set a new record for the solo flight, clocking in at 117 hours and 52 minutes, a chain of events caused the batteries to overheat. It was only after he landed that the team discovered how bad the damage was. "We made a mistake with our batteries," Piccard said after the plane touched down in July. "It was a human mistake." And a mistake that took more than nine months to fix. Fast forward to this spring, and the Solar Impulse 2 has new batteries, a new cooling system that can be manually operated by the pilot, and $20 million in fresh funding to keep the mission up and running.
[...] After several stops in the United States, the pilots hope to cross the Atlantic Ocean, and then Europe or northern Africa. They plan to return to the Middle East by late summer, completing a 35,000-kilometer (27,000-mile) trip around the world.
(Score: 2) by Techwolf on Sunday April 24 2016, @04:25PM
I like to know more about the "mistake" that cause the batteries to overheat.
(Score: 2) by rts008 on Sunday April 24 2016, @04:38PM
According to the wiki article, the batteries overheated due to 'being packed in too much insulation, and overheated'. Still sparse, but all it has to say about it.
(Score: 2) by Gravis on Sunday April 24 2016, @11:06PM
Solar Impulse 2 is powered by 17,000 solar cells and on-board rechargeable lithium batteries, allowing it to fly through the night.
...
Too much insulation caused the plane's battery temperature to spike on the first day of the flight.
[...] Solar Impulse will undergo maintenance repairs on the batteries due to damages brought about by overheating.
During the first ascent on day one of the flight from Nagoya to Hawaii, the battery temperature increased due to a high climb rate and an over insulation of the gondolas. And while the Mission Team was monitoring this very closely during the flight, there was no way to decrease the temperature for the remaining duration as each daily cycle requires an ascent to 28’000 feet and descent for optimal energy management.
Overall the airplane performed very well during the flight. The damage to the batteries is not a technical failure or a weakness in the technology but rather an evaluation error in terms of the profile of the mission and the cooling design specifications of the batteries. The temperature of the batteries in a quick ascent / descent in tropical climates was not properly anticipated.
Irreversible damage to certain parts of the batteries will require repairs which will take several months. In parallel, the Solar Impulse engineering team will be studying various options for better cooling and heating processes for very long flights.”
They are using lithium polymer batteries and overheating can cause chemical breakdown of the electrolyte. These types of batteries put off heat both while charging and discharging, so there is serious strain on batteries that are constantly doing one or the other.