EHRA-LESSIEN, Germany — A massive shortage of lithium ion battery cells could plague the global car industry in the coming decade if capacity equivalent to 40 Tesla gigafactories is not added by 2025, according to estimates from Volkswagen Group.

Ulrich Eichhorn, head of r&d for the world's largest carmaker, increased projections made just 13 months ago for his company's needs in 2025. Eichhorn's forecast is based on targets that a quarter of its group volume will come from the sale of electric vehicles by then.

"We will need more than 200 gigawatt-hours," Eichhorn told reporters on June 30 during a presentation here at the group's otherwise highly secretive proving ground a half hour drive north of Wolfsburg.

In June 2016, CEO Matthias Mueller estimated during the group's strategy announcement that Volkswagen would face "an enormous purchasing volume" in 2025 when it needs to source cells with a combined capacity to deliver 150 gigawatt-hours of electricity.

This would be enough to power a single 60-watt bulb for 2.5 billion hours, or more than 285,000 years.

Should each manufacturer also target 25 percent of sales volumes from battery-electric vehicles in 2025, Volkswagen believes global carmakers will require a supply of more than 1.5 terawatt-hours. That equates to more than 40 Tesla gigafactories, each with an annual capacity to produce 35 GWh of lithium ion cells.

"That's the demand we've extrapolated assuming other OEMs have a similar target," said Volkswagen Group researcher Linda Brinkhaus.

For that reason, German supplier Robert Bosch is considering whether to manufacture battery cells. If so, it may choose solid-state technology where there is no electrolyte liquid to transport ions back and forth when charging and discharging energy. One advantage is greater safety should a crash compromise the structural integrity of the cell.