A fuel cell technology that will offer a quick fix for dead or dying mobile phone batteries looks as if its going to be available for millions of people for the first time in the world in Japan in 2007, Japan's two biggest mobile communications carriers said Wednesday at the Wireless Japan 2005 Expo.

DMFCs (Direct Methanol Fuel Cells), which typically work by mixing methanol with air and water to produce electrical power, have for years been promoted as an alternative to lithium ion batteries used in notebook PCs and other portable electronics gear. DMFCs are useful because power can be instantly provided by inserting a fuel cartridge recharger, developers say.

A number of Japan's biggest consumer electronics companies have been developing DMFCs, but prototypes shown to date have been too big and bulky or not capable of producing enough power to be commercialized.

That seems to be changing though.

NTT DoCoMo and KDDI, Japan's number one and number two mobile communications carriers, plan to have fuel cell rechargers for mobile phones in shops the year after next, officials from both companies said.

Japan's mobile phone vendors spent years trying to get the battery life of 3G (third-generation) mobile phones to match that of the country's 2G digital phones. Next year a new problem will hit vendors as they put power-hungry digital TV receivers into phones as the country's digital TV network goes nationwide. The antennas will knock usage time back down and that's where DMFCs will help, vendors and carriers say.

In DoCoMo's case, the company has a prototype charger on display at Wireless Japan. It is developing the charger with Fujitsu Laboratories, and the device is near to making the cut for those of the carrier's nearly 50 million subscribers looking for a quick power fix, said Kazuhiko Takeno, a manager at the company's Technical Support Group.

The recharger, which is a cradle design, is still a bit bulky at 15 centimeters by 5.6 cm by 2.5 cm, and weighs 190 grams. But it has basically got enough juice to do the job. The carrier's customers can look forward to buying a commercial version around mid-2007, Takeno said.

The version on display at the Expo is a big improvement on an earlier model the company showed last September, he said.

That's because while it's about the same size and volume as the older model (the older version being marginally thinner), the new prototype has enough power to recharge a mobile phone battery three times, which is much nearer to being worthwhile for customers, he said.

The latest version uses an 18 milliliter shot of fuel, the same amount as the old model used; the prior model could only recharge a battery once, Takeno said.

Fuel-cell technology is also looking viable for KDDI's customers, according to Youichi Iriuchijima, an assistant manager at the company's IT Development Division.

At last October's Ceatec Japan 2004 exhibition, Iriuchijima showed prototype rechargers from Hitachi and Toshiba, saying improved versions would be in the shops in 2006. That schedule has slipped to January 2007, mainly because it's not until that year when regulations will be changed that will allow passengers to carry methanol on planes, he said.

Both Hitachi and Toshiba have improved their technology over the last nine months, he said.

For a start, the designs shown last October were only mock-ups and displayed under glass. This year's versions both actually produce electricity. To prove the point, he took a vial of diluted methanol and plugged it into the side of the Hitachi recharger, and the mobile phone it was supposed to power immediately sprang into electronic life.

The two working prototypes take a different approach to Fujitsu's models, however, being boxes that use cords to feed power to the mobile phones.

The Hitachi version is 12.2 cm by 7.6 cm by 2.2 cm, weighs 175 grams and offers two recharging options. A 2 ml vial of fuel, which snaps into the side of the device, can power a mobile phone for about an hour, while a 15 ml vial gives about 5 hours of power, Iriuchijima said.

The Toshiba version is bigger, at 11.7 cm by 11.3 cm by 2.5 cm, and the prototype weighs 250 grams, about twice the weight of a typical Japanese-model 3G mobile phone. But size brings power in Toshiba's case, with a 20 ml vial of fuel capable of delivering 20 hours of power, he said.

These specifications, which weren't available last year, will change for the commercial models, Iriuchijima said. He did not reveal pricing or other details.

And beyond that, KDDI was also showing even smaller versions of DMFCs that are integrated into mobile phones. These, however, were mock-ups and they were not producing electricity.

Shrinking DMFCs into sizes that can be fitted into mobile phones and having them good enough to sell will take about three years, Iriuchijima said.

"Replacing lithium ion batteries with same-size fuel cells is very difficult technology," he said.

For DoCoMo, such fuel cells may not be available until the end of the decade, Takeno said.

Wireless Japan runs until Friday at the Tokyo Big Sight exhibition center.