Does draining a Tesla’s battery turn it into a $40,000 brick?

No electric car builder has more momentum than Tesla Motors, with a new sedan going into production this year, orders for a new SUV next year and a high-volume factory coming online in California. Yet a former Tesla service agent says 2,500 Tesla Roadsters have a significant flaw: Leave them unplugged too long, and their battery packs turn into useless bricks that cost $40,000 to replace.

According to blogger Michael DeGusta, the problem comes from the Roadster's tendency to drain its batteries even when not moving; Tesla's own manuals warn that the Roadster will drain from a full charge in 11 weeks if not plugged in. DeGusta says an unnamed Tesla agent told him the company has seen five such cases so far -- and that when the charge drops to zero, the battery pack is damaged beyond repair, requiring a replacement set of 6,831 lithium-ion cells that runs $40,000. The agent even shares that Tesla was so concerned about battery damage in one case it tracked down an owner's car via its GPS system to get it charged.