BMW’s i division will build a prototype battery-powered i8 which could result in the sleek coupé switching from a petrol-electric hybrid powertrain to fully electric propulsion in the future.

The secret programme will give the i8 a significantly larger battery and a trio of new high power electric motors in place of the hybrid system it uses currently. The move comes as BMW’s i division seeks to ramp up its research operations ahead of a confirmed expansion of its existing two-model line-up around the turn of the decade.

The electric-powered car may be the successor to the current i8-based Formula E safety car next year. Also, the plan is for the i8 to be based around the carbonfibre structure developed for the BMW i division’s fuel-cell prototype, revealed last year. In order to house a series of cylindrical tanks used to stow hydrogen, it features a wider centre tunnel than the structure employed by the standard i8.

“The idea is to use the space within the widened centre tunnel to house the battery instead of the hydrogen tanks,” an official privy to the proposal currently in front of BMW’s development boss, Klaus Fröhlich, revealed to our sister publication Autocar UK. Despite the inclusion of a larger battery, sources suggest the proposed i8 prototype will not weigh more than the production version of the current i8, which tips the scales at 1,485kg and possesses a range of more than 400km.

Power for the new four-wheel-drive i8 prototype will come from three new brushless electric motors. One will be mounted up front and two at the rear in the space usually taken up by the existing i8’s turbocharged 1.5-litre three-cylinder petrol engine. Developed by BMW, the motors are claimed to operate at a much higher internal speed than the production units used by the production i8.

“BMW has a great history of high-revving combustion engines,” said an insider source. “We’re looking to take this tradition into the electric car arena with electric motors that rev far higher than those seen in production today.”

As well as providing greater power, the high-revving nature of the prototype electric motors allows them to be made in a more compact form than those in use today. “Revs are the route to making electric motors smaller,” said BMW.

In standard guise, the i8 has an overall system output of 362hp. BMW remains tightlipped on the proposed output of the all-electric prototype, but insiders say the new motors are capable of delivering up to 272hp each. However, before the aforementioned all-electric model arrives, the current hybrid i8 is due a facelift. BMW has already begun testing a more powerful version of today's i8 ahead of this planned facelift's arrival next year.