The Roadster, like the newly-updated coupe version, will go half as far again in emission-free electric mode as the previous i8. Beefed-up lithium-ion batteries – they have gone from 7.1 kWh to 11.6 kWh – now offer an electric-only range of up to 33 miles, with speeds up to 75mph possible. The electric motor driving the front wheels gets 12bhp more power (now 141bhp) while the 1.5-litre petrol triple driving the rear wheels is unchanged in power (at 228bhp) but is said to sound sportier than before.
The battery pack is charged up by recovering lost power on the overrun and during braking, and also by the petrol engine via the starter-generator unit. But as a plug-in hybrid it will also need plugging in from time to time. A full charge takes four and a half hours with standard cable or, with the iWallbox, under three hours, says BMW.
With a combined 369bhp, the new Roadster is credited with a 0-62mph time of 4.6 seconds, two-tenths behind the identically-updated coupe. The Roadster’s fuel consumption suffers more next to the coupe, but then it still records 134.5mpg on the combined cycle. For mixed driving the new beefier batteries of both Roadster and coupe should give a boost to real-world consumption (realistically, 40-50mpg) by ensuring the electric motor does more of the work, leaving the petrol unit idle more often.