Say what you will about Tesla Motors chief executive Elon Musk, he's one of the very few global automaker CEOs who personally responds to owner questions via Twitter.

And he's at it again, promising late Friday afternoon that details will be coming this week on the promised battery upgrade for the Tesla Roadster sold in the U.S. from 2008 through 2011.

DON'T MISS: Tesla Roadster To Get Replacement Battery, 400-Mile Range: Musk (Aug 2014)

"Roadster update details coming next week," Musk tweeted in response to a question from Twitter user Manfred Hillinger.

"Several crisis issues [with] higher priority pushed this out longer than expected."

'Revenge of the Electric Car' premiere: Elon Musk arrives in a Tesla Roadster

'Revenge of the Electric Car' premiere: Elon Musk arrives in a Tesla Roadster

In a July interview with British car magazine Auto Express, Musk said Tesla would offer a "new-generation battery pack" with "a range of about 400 miles" for the Roadster.

That, he noted, would be sufficient to let owners travel from Los Angeles to San Francisco without stopping

ALSO SEE: Battery Life In Tesla Roadster Is Likely Better Than Predicted (Jul 2013)

Unlike the company's Model S electric luxury sedan, most versions of which have been fitted with Supercharger DC quick-charging capability, the 2,500 Roadsters sold did not incorporate quick charging.

So a new battery pack offering 400 miles of range will get Roadster drivers closer to the practicality that Model S drivers enjoy today for long-distance trips.

Tesla Roadster final assembly, Menlo Park, California, April 2009

Tesla Roadster final assembly, Menlo Park, California, April 2009

The question of whether Tesla might also add Supercharger capability to its Roadsters hasn't been directly addressed.

The Roadster battery pack, containing 6,831 small cylindrical lithium-ion cells, is rated at 53 kilowatt-hours of energy and 265 miles of range.

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Also left unaddressed until Tesla releases details of the Roadster pack upgrade is any discussion of the cost.

The Roadster ended its limited production run in 2011 at a price of $109,000, and a battery upgrade seems highly likely to cost five figures.

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