Liquid electrocar batteries could be replaced at pumps

Remorseless German boffins have come up with a solution to long recharge times for electric vehicles. They propose the use of liquid-electrolyte batteries, so that a 'leccy car could have discharged electrolyte pumped out and replaced with fully-charged liquid at filling stations.

The proposals come from the Fraunhofer Institute for Chemical Technology (ICT) near Karlsruhe. The engineers there suggest the use of a well-known technology known as a 'redox' battery, in which two fluid electrolytes containing metal ions flow through porous graphite felt electrodes, separated by a membrane which allows protons to pass through it.

The Fraunhofer battery-boffins say that redox batteries have until now suffered from rubbish capacity compared to the li-ion units now being deployed in advanced electrocars, preventing their use. But they say this has now been cracked.

"We can now increase the mileage four or fivefold, to approximately that of lithium-ion batteries," said Jens Noack of the ICT. "These batteries can be recharged at the gas station in a few minutes."

Most electric vehicles now in service are actually powered by lead-acid batteries, but there are a few - for instance the Tesla Roadster - which use li-ion. It's generally thought that li-ion performance or something like it is the minimum that mainstream motorists of the future might accept, but as Noack says the crippling defect of this tech is the long recharge time.

Redox batteries could, by the sound of it, solve this problem - and solve it a bit more easily, perhaps, than alternative schemes where garages would have loads of massive, ready-charged-up, standardised li-ion batteries on hand waiting to be craned into vehicles in place of dead ones.

On the other hand there's the promise of li-titanate batteries, with similar performance to ordinary li-ion but able to charge up in less than ten minutes from an industrial power outlet. This would be more convenient still, and it's apparently further down the road to commercialisation.

Noack's kit may well be better, but there are dozens of examples from the history of technology to show that better doesn't always win: and even the electric car itself has rivals in the race for the future of road transport. ®