Nikola is relying on californian manufacturer romeo power technology for batteries for one of its prototype electric trucks, according to documents seen by the financial times and a person familiar with the work.

The use of an established industry supplier is the second example of the start-up outsourcing a key technology, months after it touted its own game-changing battery, which it said it would demonstrate this year.

Earlier this month, nikola agreed to purchase general motors ultium battery for its badger pick-up truck, as part of a $2bn deal in which gm is taking an 11 per cent stake in the company.

Excitement for nikolas technology has helped propel its shares this year, to the point that it was briefly more valuable than ford, but it is now fighting allegations that it repeatedly misrepresented its progress and does not have the proprietary technology it claimed.

Romeo power, a battery pack maker located in an industrial zone just outside los angeles, is supplying battery packs to nikola to use in prototype commercial trucks, the documents show. the technical documents include diagrams, product specifications and a plan for testing the battery packs.

A person familiar with the matter said romeo power is supplying the battery for the prototype nikola tre, which is being built at cnh industrials iveco plant in ulm, germany.

Nikola declined to comment. romeo power did not return messages seeking comment.

Romeo power was founded in 2015, and the staff includes employees from spacex, tesla, samsung and amazon. the company supplies battery packs for trucks and buses, and major auto parts manufacturer borgwarner in michigan owns 20 per cent of its corporate parent.

Nikolas business relationship with the los angeles company had begun at least by january 2020, according to dates on the documents.

In november 2019, nikola said it had technology that would double the range of current electric vehicles to 600 miles without increasing the batterys size or weight. trevor milton, the companys founder, at the time called it the biggest advancement we have seen in the battery world.

Last week short seller hindenburg research published a report calling nikola an intricate fraud and disputing its claims to have developed breakthrough technology. the us securities and exchange commission and department of justice are making inquiries about the company.

In a rebuttal on monday, nikola said hindenburgs report contained false and misleading claims, but added the company does use third-party parts in prototype vehicles. it noted this is common practice among vehicle manufacturers and said nikola may swap in its own parts during production.

Nikola also said it is working with an academic institution to advance battery tech and is excited for potential breakthroughs.

Nikola board member steve girsky said at an ft due diligence event on thursday that the company sometimes relied on suppliers. other supporters have described the company as a systems integrator that orchestrates how other companies tech is used in a vehicle.

On september 11, the day after the hindenburg report was published, mr milton tweeted photographs showing a tre prototype being assembled in ulm. f the haters, he wrote in the tweet. well come back stronger from the lies spread about us.

A person familiar with the technology said the photos included battery packs from romeo power.