Boeing employees walk around a 787 Dreamliner scheduled for delivery to All Nippon Airways (ANA) parked next to the Boeing Everett Factory at Paine Field in Everett, Washington September 26, 2011. Boeing Co workers hand-delivered -- literally -- the company's first 787 Dreamliner in the pouring rain on Monday to All Nippon Airways, capping nearly a decade of development of the world's most advanced jetliner. The first 787 Dreamliner for ANA, which is not the one pictured here, will fly from Everett to Japan on September 27. REUTERS/Anthony Bolante

TOKYO/WASHINGTON - The U.S. National Transportation Safety Board on Sunday ruled out excess voltage as the cause of a battery fire last month on a Boeing Co 787 Dreamliner jet operated by Japan Airlines Co and widened its investigation to include the Arizona-based manufacturer of the battery’s charger.

Last week, governments across the world grounded the Dreamliner while Boeing halted deliveries after a problem with a lithium-ion battery on a second 787 plane, flown by All Nippon Airways Co, forced the aircraft to make an emergency landing in western Japan.

“Examination of the flight recorder data from the JAL B-787 airplane indicates that the APU (auxiliary power unit) battery did not exceed its designed voltage of 32 volts,” the NTSB said in a statement forwarded by a Boeing Japan representative.

On Friday, a Japanese safety official told reporters that excessive electricity may have overheated the battery in the ANA-owned Dreamliner that was forced to make the emergency landing at Japan’s Takamatsu airport last week.

U.S. investigators have examined the lithium-ion battery that powered the APU, where the battery fire started in the JAL plane, as well as several other components removed from the airplane, including wire bundles and battery management circuit boards, the NTSB statement said.

On Tuesday, the NTSB said U.S. investigators will convene in Arizona to test and examine the charger for the battery, and download non-volatile memory from the APU controller, while other components have been sent for download or examination to Boeing’s Seattle facility and manufacturer facilities in Japan.

Securaplane Technologies Inc, a unit of Britain’s Meggitt Plc, on Sunday confirmed that it makes the charger for lithium-ion batteries used on the 787, and said it will fully support the U.S. investigation.

Shubhayu Chakraborty, president of Securaplane, declined to comment on the NTSB’s planned visit, but said his company would support the investigation.

“At this time we are not really involved in the investigation. If and when we get involved, we will support it fully,” he told Reuters.

Securaplane is making a lithium-ion battery system for the KC-390 military transport plane being built by Brazil’s Embraer , which is due to have its first plane in 2014.

The company is also developing backup batteries for the Embraer 450/500 business jet and will make the lithium battery for the next-generation Eurocopter EC-135 helicopter being developed by EADS, according to the company’s website.

Japan’s GS Yuasa Corp makes lithium-ion batteries for the Dreamliner, while France’s Thales produces the control systems for the battery.

In its statement, the NTSB said French authorities were also participating in the investigation.

Japan Transport Safety Board said it was aware of the NTSB report and would consider the U.S. statement in its probe.

The NTSB said the Japanese agency was participating in its investigation of the Boston incident, while NTSB officials were helping the agency with its investigation of the emergency landing in Japan. Both investigations were ongoing.

“There’s nothing more I can add at this point as we still haven’t started our investigation into the battery here,” JTSB inspector Hideyo Kosugi told Reuters.

“The NTSB’s investigation started earlier. We still haven’t taken X-rays or CT-scans of the battery. In our case, both the battery and the surrounding systems are still stored in (Tokyo’s) Haneda (Airport) as the third party organization where the Japanese investigation would take place still has not been chosen.”

Boeing said on Friday it would continue building the carbon-composite 787, but put deliveries on hold until the U.S. Federal Aviation Administration approves and implements a plan to ensure the safety of potentially flammable lithium-ion batteries.

In Washington, the top U.S. transportation official Ray LaHood said the 787, which has a list price of $207 million, would not fly until regulators were “1,000 percent sure” it was safe.

Japan is the biggest market so far for the 787, with ANA and JAL operating 24 of the 290-seat wide-bodied planes. Boeing has orders for almost 850 of the planes.