A new retro-fit hybrid conversion that unlocks the potential to save 61% on fuel costs and lower tailpipe emissions by 39% has been launched.

The conversion, which has a removable battery pack, upgrades existing vehicles to hybrid technology.

However, the technology, which was developed in the UK by MIRA engineers, will be sold only to carmakers for use on new models.

A demonstrator has been built around a Skoda Fabia.

As a “plug-in hybrid” the vehicle can charge its Lithium Ion Phosphate batteries by running its engine or by plugging into the mains.

The advantage with this new system is that the lightweight battery pack – about 11kg – can be lifted out of the car for recharging.

“Despite advances in powertrain technology you can still obtain electricity from your domestic provider far cheaper and greener than you can produce it via an automotive combustion engine, so ‘plug-in’ hybrids make sense,” said Derek Charters, MIRA’s advanced powertrain manager.

“With this project we’ve removed the primary limitation of the ‘plug-in hybrid’ concept by allowing the battery pack to come to the mains, rather than having to park right next to a socket.”

The 50/50 hybrid derives power jointly from a 60Kw petrol engine at the front and two 35KW inboard motors powering the rear wheels though MIRA’s e-differential.

The H4V returns 64mpg, as measured on the EU drive cycle.

Whilst general levels of performance, such as top speed and acceleration are similar to standard.

As an evaluation tool, the demonstration vehicle is not for public sale, so the project received support through the Energy Saving Trust’s (EST) Low Carbon R&D programme, which is funded by the Department for Transport.

“This project has designed a new system allowing hybrids to be more flexible and practical for every day use,” Philip Sellwood, EST chief executive, said.

“With over 20% of the UK’s total carbon emission produced by road transport every year, these advances in technology are vital.”