A hacker appears to have leaked Elon Musk's next big upgrade for the Tesla Model S

Tesla fans appear to have discovered the next iteration of the Model S: An as-yet unannounced, more powerful version that sports a 100 kilowatt-hour battery.

The most advanced Model S you can buy today comes with a 90 kWh battery and can grant its driver a driving range of nearly 290 miles (466km) . A bigger battery would mean extending that range even more - potentially exceeding 300 miles on a single charge - or give the car greater performance.

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The tinkerer who unearthed evidence of the new car, Jason Hughes, found mention of a mysterious "P100D" buried in the software that runs Tesla's cars. Considering that the top-of-the-line Model S is named the P90D, where the "90" is a reference to the battery capacity, Hughes and other Tesla enthusiasts reason that a P100D would improve on existing batteries by 10 kWh.

Tesla owners report getting about 3 miles per kWh, so it's conceivable that an extra 10 kWh could add as many as 30 miles to the range of the Model S, depending on how you drive.

A P100D would be a "performance" model, meaning you'd probably take a slight hit to fuel economy over a Model S that was marketed as a simple 100D.

Still, adding 10 kWh would be even more significant than Tesla's last battery upgrade, which bumped the P85D up to the P90D.

Hughes tweeted the results of his software hacking at Elon Musk:

"@elonmusk@teslamotors#tesla I know your secret."

Hughes's car then tried to download a new software update - which the white-hat hacker thought was Musk trying to retaliate. But Musk disavowed the move - before commending Hughes for his actions:

"@wk057@TeslaMotors Wasn't done at my request. Good hacking is a gift."

Tesla is expected to unveil a low-cost electric sedan, the Model 3, later this month.