A prototype electric vehicle wearing the latest BMW 7 Series body has been spied on a trailer full of BMWs.While BMW may be preparing an electric version of the current 7 Series sedan, it hasn't appeared as part of the company's announced electric car roster, which includes the 2020 iX3 crossover, 2021 i4 four-door "coupe" and the production version of the iNext.It's more likely this car is an evaluation mule for an electric version of the next-generation 7 Series which, if the company follows its typical seven-year model cadence, should debut in 2021.A report in September claimed BMW was preparing two versions of its electric 7 Series: a standard model with 410kW of power and a 100kWh battery pack, and a more powerful S variant with 500kW, and a larger 120kWh battery with 580 kilometres of range.It's unclear how visually distinct the i7 will be from its petrol, diesel and plug-in hybrid 7 Series siblings. It could follow in the footsteps in the iX3 and i4 in sticking closely to the parent vehicle.Alternatively, it could have a body and interior all of its own, like the iNext crossover.MORE: i7 coverageMORE: BMW news, reviews, comparisons and videos

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