SEATTLE Boeing says it continues to work with the Federal Aviation Administration to come up with a solution to prevent more lithium ion battery fires aboard 787 Dreamliners.

Fifty 787s in the hands of airlines continue to sit parked on the ground worldwide, and test flights by Boeing for new jets rolling out of the Everett and North Charleston, South Carolina factories are not yet cleared. No time frame for a solution is in sight.

Last Wednesday, the main battery in the forward section of an All Nippon Airways 787 smoked and leaked electrolyte 20 minutes into a domestic flight from western Japan to Tokyo. Two weeks ago, the rear battery aboard a Japan Air Lines 787 caught fire 15 minutes after the last passengers got off at Boston s Logan Airport.

Those incidents have low led to investigations by both the U.S. National Transportation Safety Board and the Japan Transportation Safety Board.

Monday in the Japanese city of Kyoto, U.S. and Japanese investigators visited GS Yuasa, the maker of the batteries. Tsutomu Nishijima, a spokesman for the company said the battery maker was cooperating fully with the probe. Monday s meeting involved an introductory meeting and a factory tour. Next, the team will become involved with studies into product quality. GS Yuasa would not comment on details of the investigation.

Japanese investigators said Friday that the ANA battery showed signs of overcharging, and having received voltage in excess of its design limits. In a news release issued over the weekend, the NTSB said voltage in the Boston incident did not exceed 32 volts, which is the voltage the battery system is designed around. While that is being interpreted as meaning the battery was not overcharged, battery experts say unless the charging system cuts the flow of electricity to the battery, over-charging is still possible.

Tomorrow, the NTSB says it will visit Securaplane Technologies in Tucson, Arizona. Securaplane makes the charging system. The NTSB says it will also look at wiring bundles and battery management circuit boards. The rear battery in the Boston case works the plane s Auxiliary Power Unit, a small turbine engine that s mounted in the tail of the plane to provide power to the plane s systems on the ground and can be used to start the engines. The NTSB says components of the APU will be tested as well.

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