Tesla Model S 70D already equipped with 75-kWh battery

Owners can reportedly call in and unlock the extra range for $3,250.

Tesla Motors is reportedly equipping its latest Model S 70D sedans with a larger 75-kWh battery pack from the factory, however the extra capacity is said to be locked via firmware restriction.

Rather than build both a 70-kWh and 75-kWh battery pack, or force all customers to pay for the larger module, the company will use the same battery for both variants, according to a Teslarati report.

Anyone who buys the latest Model S 70D can have the extra capacity -- and extra range -- unlocked via a firmware update, for a reported $3,250 upgrade fee.

"Yes, all 70 kWh Model S with updated styling have been built with a 75 kWh battery pack and the additional energy can be unlocked at any time through an over-the-air software update," the company said in a statement to Autoblog. "We will continue to offer the 70 kWh energy option but we will no longer produce the packs; a decision that is the most efficient for Tesla and the most beneficial for our customers."

It is unclear if Tesla's support staff will be able to temporarily unlock the extra capacity, if an owner accidentally ends up disabled on the side of the road after exhausting all 70-kWh. In theory, a simple over-the-air command could allow the driver to get to a charging station or at least to a safer location.

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