A battery that overheated on a Boeing 787  flight in Japan and forced the plane to make an emergency landing was  incorrectly wired, an investigation has found.

The All Nippon Airways (ANA) Dreamliner  touched down in Takamatsu when the lithium ion battery sparked an on-board fire,  prompting the worldwide grounding of the Boeing 787 jets due to safety  concerns.

Japan’s Transport Safety Board has said the  battery for the aircraft’s auxiliary power unit was improperly connected to the  main battery, which overheated during the flight.

The board’s report said a protective valve  would have prevented power from the auxiliary unit from causing damage,  the Huffington  Post said.

The fact that lights on the  aircraft’s tail  and wings were flickering after the emergency landing,  and that the main  battery was switched off, led investigators to  conclude there was an abnormal  current travelling from the auxiliary  power unit.

This was down to miswiring, the report  said.

The Transport Safety Board will carry out  further analysis to determine  what caused the main battery to overheat and  begin smoking.

The incident on January 16 came days after a  battery exploded on a Dreamliner parked at Boston’s Logan International  Airport.

A mechanic conducting a routine  post-flight  inspection on the Boeing 787 jet discovered smoke in the  cockpit.

Passengers had disembarked the plane just 15  minutes before the blaze broke out.

After the fault on the ANA domestic flight on  January 16, the Federal Aviation  Administration and aviation authorities in  other countries took the  decision to ground 787 fleets.

The Boeing 787 is the first airliner to make  extensive use of lightweight lithium ion batteries.

The batteries are quicker to charge and  contain more energy than  conventional batteries of the same size, but are also  more susceptible  to overheating.

Aircraft manufacturer Airbus has switched  from lithium ion batteries to traditional nickel-cadmium batteries for its new  A350 passenger jet in the wake of the problems plaguing competitor Boeing’s  Dreamliner fleet.

It said it had taken the decision to prevent further delays in delivering its new new passenger jet amid uncertainty over whether the investigations into Boeing’s battery problems will lead to a regulation overhaul.


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