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WASHINGTON -- U.S. safety inspectors ruled out excess voltage as the cause of a battery fire on a Japan Airlines Boeing 787 Dreamliner on Jan. 7 in Boston, but they said there could still be problems with wiring or other charging components.
An examination of the flight data recorder indicated that the battery didn't exceed its designed 32 volts, the National Transportation Safety Board said Sunday.
Investigators plan to meet Tuesday with officials of Secu-raplane Technologies Inc., manufacturer of the charger for the 787's lithium ion batteries, at the company's headquarters in Tucson, Ariz., said Kelly Nantel, an NTSB spokeswoman. "We're not prepared to say there was no charging issue," she said.
Still, it's possible that the battery failures in that plane and in an All Nippon Airways plane that made an emergency landing in Japan last week may be due to a charging problem, according to John Goglia, a former NTSB board member and aviation safety expert.
Too much current flowing too fast into a battery can overwhelm it. That may cause it to short-circuit and overheat even if the voltage remains within its design limit, he said.
"The battery is like a big sponge," Goglia said. "You can feed it with an eye dropper or you can feed it with a garden hose. If allowed, it will soak up everything it can from the garden hose until it destroys itself."
An investigator in Japan said Friday that the burned insides of the Japan Airlines plane's lithium ion battery show the battery received voltage in excess of its design limits.
Since then, all 50 of Boeing's 787s that were delivered to airlines have been grounded, and the manufacturer has halted deliveries of new planes.