BMW said it was investing $10 million in a new battery assembly line which will be capable of operating in a two shift system ahead of the introduction of the BMW X3 plug in hybrid vehicle by the end of the year.

BMW made 15,000 batteries last year with a one shift system and currently produces a plug-in hybrid version of the X5 offroader. A new version of the X5 will be produced at the Spartanburg plant from August onwards, the company said.

BMW said it planned to employ 120 staff to manufacture different types of batteries, and the additional staff gave it the capacity to double production.

In the past four years BMW workers assembled 45,000 batteries, the carmaker said.