Volkswagen , Northvolt's top shareholder, has significantly written down its 21% stake in the Swedish battery cells maker that filed for bankruptcy protection in the United States last week, two people familiar with the matter said.

Volkswagen bet big on European-made batteries a few years ago with two massive investments in Northvolt, the Swedish manufacturer. Now the automaker’s €1.4 billion stake is worth less than half that, according to Reuters. The write-downs occurred throughout the current fiscal year as the situation at Northvolt deteriorated.

Volkswagen has written down the majority of its 21 per cent stake in Northvolt over the past year ahead of the Swedish battery maker’s filing for Chapter 11 bankruptcy, according to people close to the German carmaker.