BERLIN, April 9 (Reuters) - BMW and Croatia's Rimac have agreed to partner on high-voltage electric vehicle battery technology, they said on Tuesday, a European tie-up aimed at challenging Asian dominance in the field.

Rimac, an electric hypercar maker owned 45% by Porsche AG , is expanding its reach as a supplier of battery systems and powertrain components to other automakers, with the aim of reaching 100,000 batteries a year between 2024 and 2026.

Automakers are under increasing pressure to cut capital spending on electric vehicles. Premium EV startup Lucid is also trying to augment relatively small sales of its own EVs by selling its electric drive technology to other automakers such as Aston Martin.

Rimac CEO Mate Rimac said in 2023 that an undisclosed German carmaker would use a Rimac battery system in a high-performance model - with annual production of around 40,000 units - starting this year, with more signed up.

BMW declined to provide further details on which batteries or models would be developed in the partnership, saying only that it did not apply to the new cylindrical batteries powering the 'Neue Klasse' EV line which goes into production in 2025.

The German carmaker hit an all-electric sales share of 15% last year and has said it expects that figure to reach 50% well before 2030.

BMW has its own battery cell research centre in Germany, but has left large-scale development to partners, placing multi-billion-euro orders with CATL, and EVE Energy to produce battery cells in China and Europe.

(Reporting by Victoria Waldersee, Joe White, Nick Carey; Editing by Emelia Sithole-Matarise)