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.

Other electric vehicles on the road do not seem to pose similar pitfalls. The Nissan Leaf will shut itself off completely before draining its battery entirely, and the Chevy Volt performs a similar trick if it ever reaches a state where its batteries are discharged and the gas engine has no fuel. But DeGusta maintains that Tesla has been less than forthcoming about the dangers to owners of a complete rundown, simply urging customers to plug in regularly -- and warning in its warranty that battery damage from negligence will not be covered.

No complaints of Roadster bricking have been reported to federal safety officials, and there's been no similar complaints on popular Tesla owners' forums. Those forums also note that two of the five examples described by DeGusta -- who says he's paid a deposit for a Tesla Model X -- seem sketchy. One involves someone who hauled their Roadster to Japan and couldn't get the voltage to work there, which is odd because Japan uses the same electrical standards as the United States. The other involves an owner who tried to charge his Tesla with a 100-foot extension cord, which while odd should still work.

Tesla did not return a message seeking comment, and has said little in the past about the cost of replacing its battery pack. Tesla enthusiasts would say this problem is simply akin to making sure a gas engine always has oil -- but refilling an engine without oil solves the problem, while no jump start appears capable to revive a dead Roadster battery. Electric vehicles already suffer from the burden of range anxiety, and Tesla's sales job becomes that much harder if it has to ease battery anxiety too.

Top Photo: Tesla