BMW i Ventures and Generation Investment Management have added $55m in series 6 funding to the $140m that the electric bus maker closed in January.

US-based electric bus producer Proterra completed what it called a series 6 round yesterday, raising $55m from automotive manufacturer BMW’s i Ventures unit and investment firm Generation Investment Management.

Proterra develops and produces all-electric buses, and has sold more than 400 vehicles to a total of 39 transit agencies across the US. The funding will support the expansion of its manufacturing capabilities and research and development activities.

The round took Proterra’s overall debt and equity financing to $410m since it…