Tesla seeks to boost range of electric roadster

Tesla Motors said Friday that it is giving some new attention to owners of its original roadster, a pioneering, two-seat, first electric car that paved the way for its current, headline-grabbing Model S sedan.

Tesla says in a blog post that it's going to offer three big improvements to the roadsters, its first electric cars, which should improve range by 40% to 50%. Under certain conditions, the improvements could allow the roadster to be driven up to 400 miles on a single charge, Tesla says. That's important because the roadster can't use Tesla's network of high-speed charging stations along major interstate highways, dubbed "superchargers." The network is one of the key selling points for the Model S.

Here are the three big improvements:

• Battery. The one likely to get the most attention is a new battery. The roadster's battery, the first lithium-ion cell to go into any production vehicle, was "state of the art in 2008, but cell technology has improved substantially since then," Palo Alto-based Tesla says in the post. It says a replacement battery packs in 31% more energy than the original, which will extend the car's range.

• Aero kit. Tesla is going to offer a retrofit body kit that it says will make a 15% improvement in the roadster's coefficient of drag. The original had a drag coefficient of 0.36. With the kit, it drops to 0.31.

• Tires. New tires with better rolling resistance have come a long way, deemed about 20% better when it comes to reducing drag. Tesla says it is also improving wheel bearings and residual brake drag to reduce overall rolling resistance.

Despite the latest updates, Tesla says it isn't done with improvement to the roadster, which is no longer in production.

"We are confident that this will not be the last update the roadster will receive in the many years to come."