Honda Motor has brought the mass production of zero-emission hydrogen vehicles a step closer to reality by developing a cheaper-to-make, high-performance fuel cell stack needed to power the cars, Reuters reported.

The news agency reported that Honda on Friday claimed the new fuel cell stack is lighter, smaller and 10% more fuel efficient than the fuel cell it now uses and can operate in temperatures as low as minus 20C (-4F). Its current fuel cell vehicle (FCV) can only run in above-freezing conditions, Reuters noted.

Reuters said FCVs are touted as the ultimate "green cars" since they emit only water as a by-product, creating electricity by combining hydrogen and oxygen, but mass production is believed to be at least a decade away due to high costs and lack of infrastructure to supply and store hydrogen.

Reuters said Honda declined to give details on the scope of cost reduction the new technology would achieve, but Yuji Kawaguchi, senior chief engineer at Honda R&D Co, reportedly said cost savings were "big".

A petrol engine can produce one kilowatt of energy for about $US50, while a one-kilowatt fuel cell on the market today costs around $5,000, Reuters said.

"We want to be able to sell the fuel cell stack as soon as possible, although we have no concrete plans at the moment," Kawaguchi told Reuters.

The news agency said Honda's new fuel cell stack features a separator made of metal that is stamped together, compared with conventional separators made of carbon that need to be fastened with bolts - the new technology almost halves the number of components, bringing down production time and costs.

The stack also uses newly developed "aromatic" electrolyte membranes made of petroleum-based material instead of the more expensive and complex fluorine electrolyte membranes used in Honda's current FCV, Reuters added.

The new features also increase driving range by 40 km (25 miles) to 395 km (245 miles), although that is short of the minimum 500 km (300 miles) believed to be needed to make FCVs truly practical, the report said.

Reuters said Honda is one of only a handful of car makers with a saleable FCV on the road, but it has been using fuel cells developed by Canada's Ballard Power Systems with whom it has a three-year supply pact until 2005.

Kawaguchi told Reuters Honda's new fuel cell stack is better than any on the road now, but stressed its relationship with Ballard would not change.

"We will continue to cooperate and compete with Ballard," he said, according to the news agency.