* New technology can charge full-sized bus during 15 second stop
* Flash chargers eliminate need for overhead power lines
* Growing numbers of "megacities" to drive demand
* ABB sees road transit as major new market
ZURICH, May 30 (Reuters) - Swiss firm ABB has developed technology that can charge a full-sized electric bus during ordinary stops, removing the need for overhead lines in major cities it believes will turn away from traditional engines in the battle with pollution.
Claes Rytoft, acting chief technology officer at ABB, said the new system takes only 15 seconds to charge a bus carrying 135 people with enough power to reach the next stop and fully charges the battery in just 3-4 minutes at the end of the line.
The world's biggest supplier of power grid technology expects the growing number of cities with populations stretching into the tens of millions will drive an electrification of the transport network, as governments look to cut pollution, improve air quality and reduce dependence on oil.
Yet it is investing in the technology at a time when several high-profile electric car initiatives have failed or fallen short of their goals, including the bankruptcy of Israeli venture Better Place earlier this week.
ABB said it was working on a pilot project with Geneva's public transport company and Geneva Power Utility SIG to install a series of chargers between the city's airport and its international exhibition centre, Palexpo.
Rytoft said because the technology eliminates the need for overhead power lines, it makes electric buses cheaper to install and more visually appealing.
"The key element for ABB in this project is power conversion and electrical motors, which are our core technologies and we are always interested in new applications for these technologies," he told Reuters in an interview.
"It's not unusual for us to supply the transportation industry as such, but the focus so far has been on rail. Now we're looking to add mass transit."
ABB's rail business had sales of $1.2 billion in 2012.
Rytoft declined to speculate on the potential size of the market for flash-charging technology, but said the uptake would depend on the costs of electric batteries and fuel prices.
According to a 2012 study by Pike Research, global sales of electric buses are expected to quadruple to 20,000 per year by 2018 from 5,000 last year.
ABB's new type of automatic flash-charging mechanism allows batteries on the roof of buses to be charged in 15 seconds with a 400 kilowatt boost, as passengers get on and off the bus.
ABB has also invested in fast-charging technology for electric cars and last year announced a 6-million euro deal to build 200 fast-charging stations in Estonia.
ABB produces chargers that use both direct current (DC) and alternating current (AC). Because DC can carry heavier loads, a battery can be recharged in 15-30 minutes, compared to the six to eight hours it takes with a lower-voltage AC unit.
"These small initiatives help to generate momentum for infrastructure needs in a bigger context. In the end this all adds up for a need to reconfigure energy infrastructure to a more efficient one," said ZKB analyst Richard Frei.
"Plus, fast chargers for buses mid- to long-term could become a mass business ... if it becomes attractive they can become a big player. And if some of those initiatives fail, it's not too costly." (Editing by Patrick Graham)