Tesla's roadster, in a dealership / Getty Images

CEO Elon Musk had teased that the car would be updated last week

Tesla has updated its sporty Roadster electric car, improving its range by as much as 50%.

The company has updated the battery, as well as the car’s aerodynamics and resistance, to allow it to get as drive as far as 400 miles on one charge.

Customers with the old car will be able to upgrade them to the new package.

The new battery stored 31% more energy than the battery in the original car, said Tesla. The first car had the first ever lithium ion battery every put into a production vehicle, and while it was once state of the art battery technologies have moved on, it said.

The company also reduced the drag of the car, which it said will improve the aerodynamics by 15%. It also reduced the rolling resistance, using new tires and wheel bearings that will give a roughly 20% improvement to the drag on the car.

Tesla will be making appointments to upgrade Roadsters once the car’s new battery has received safety approvals.

CEO Elon Musk teased the upgrade earlier in December, saying that "several crisis issues w[ith] higher priority pushed this out longer than expected".

It expects that “this will not be the last update the Roadster will receive in the many years to come”, it said. There will be no major updates to the Model S, Tesla’s saloon.

The company will be demonstrating the range of the new car in  a non-stop drive from San Francisco to Los Angeles in the early weeks of 2015, it said.