"Thus far, people can charge mobile phones only at home or at the office. Many people want to charge their handsets while they are traveling. 'Mobile' recharging is one of important targets of fuel-cell development," said Katsuhiko Takeno, manager of the technical support group at Docomo's customer equipment development department.

Docomo jointly developed the fuel cell with Fujitsu Laboratories Ltd., which has expertise in both mobile phone and fuel cell technologies. Docomo said it seeking other partners to work on the project.

The team designed a cradle with a fuel cell to recharge mobile phones. Initially, the fuel cell would not be used to directly power a phone. "Lithium ion batteries will continue evolving to provide higher performance, and Docomo believes that lithium ion batteries will stay as the mainstream for mobile phones for another five or ten years," said Takeno. "Fuel cells will make up for what lithium ion batteries lack."

Using an 18-cc cartridge containing a methanol solution at 30-percent concentration, the charger is designed to provide an output power of 700 mA at 5.4 V, the same output level required for present chargers bundled with Docomo's 3G Foma handsets.

The fuel cell consists of an electroconductive film sandwiched by an anode and cathode. The scheme can generate about 50 mW/cm³ of electricity. The prototype can power phones for about two hours of continuous use.

Docomo said it plans to complete development by March 2006. It will offer the mobile recharger commerically as early as possible in 2006. By then, Docomo expects to reduce size and increase fuel cell performance so it can charge lithium ion batteries three times with one fuel cartridge. Docomo expects to introduce mobile phones with a built-in fuel cell rechargers as early as 2007.

Docomo is setting specifications for rechargers, and intends to make new handsets and fuel cells compatible with the specifications later this fall.