BMW North America is being hit with a national class action lawsuit over alleged defects of the range-extending i3.

In October 2014, Consumer Reports took the BMW i3 REx for a spin and discovered a loss in power at exactly the most inappropriate moment, when the test driver was attempting to pass a truck. After conducting a series of follow-up tests, CR noticed prolonged trips “dramatically” affected the car’s ability to accelerate.

Shortly after the i3’s problems made the news, BMW announced a series of updates to the i3 for the spring of 2015. The car did receive a software update in March last year which brought several tweaks, along with a warning of possible power reduction whenever the charge level dropped to two percent.

However, the problems for BMW are far from being over as the company’s North American division now faces a national class action lawsuit for alleged defects in the range-extending i3. Filed by MLG Automotive Law on Tuesday in U.S. District Court in Los Angeles, the lawsuit refers to the car’s 34-hp two-cylinder gasoline engine which “doesn't produce enough power to prevent a dramatic decrease in the vehicle's performance.”

It seems that whenever the i3 REx is under heavy load, like when carrying several passengers and/or when going up a hill, the speed significantly decreases as the battery level drops. According to the lawsuit, the repercussions are quite severe, with the car slowing down to 45 mph (72 kph) on the highway without warning the driver beforehand.

According to Jonathan Michaels, founding member of MLG Automotive Law., “The BMW i3 Range Extender feature is a dangerous instrumentality to the owners of the vehicles and to other motorists on the road.” He goes on to specify “Having a sudden and unexpected loss of power in a motor vehicle can result in a catastrophic situation for all those on the road. These cars are dangerous and should not be driven.”

The national class action lawsuit wants BMW to fix all the problematic i3 REx units and provide compensations to affected owners. In addition, the plaintiff seeks a halt of i3 sales until the alleged problems are ironed out.

You can read all about the lawsuit in the press release area.

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