AUSTIN, Texas, Dec 21 Reuters Elon Musk says prototypes are easy, production is hell. And when it comes to the longawaited Cybertruck, Tesla39;s hell is its pioneering 4680 battery.

Tesla delivered the first of its futuristic stainless steelplated electric pickups last month and CEO Musk said in October that it would probably hit an annual production rate of a quarter of a million vehicles at some point during 2025.

But Tesla is still a long way off that kind of production pace, and one of the main bottlenecks is the speed it can make the 4680 batteries used in the Cybertruck with its new drycoating technology, nine people familiar with the matter said.

Tesla39;s Giga Texas factory is currently churning out 4680 battery cells at rate only sufficient to power about 24,000 Cybertrucks a year, or about a 10th of the required output, according to Reuters calculations based on a combination of public data and unpublished figures provided by sources.

Being able to ramp up battery output massively by drycoating electrodes rather than using the slower, more costly wetcoating was a key factor behind Tesla39;s forecasts in 2020 that it would more than halve battery costs, cut investment significantly, and create smaller, greener factories.

The nine people, who spoke to Reuters on condition of anonymity because of the sensitivity of the matter, said Tesla had yet to crack drycoating at the industrial scale needed to make 4680 batteries fast enough to hit its production…