Why a Nissan Leaf can’t get “bricked” like a Tesla Roadster

After this morning's story on how the Tesla Roadster's battery pack can turn into a $40,000 paperweight if drained completely, Tesla admitted the story was correct -- but that it gave owners plenty of warning, and suggested other cars could suffer the same fate. Except the only other electric vehicle on the market, the Nissan Leaf, is built to avoid this very problem.

Despite repeated calls and messages, Tesla still hasn't responded to us -- but they gave this statement to Engadget:

All automobiles require some level of owner care. For example, combustion vehicles require regular oil changes or the engine will be destroyed. Electric vehicles should be plugged in and charging when not in use for maximum performance. All batteries are subject to damage if the charge is kept at zero for long periods of time. However, Tesla avoids this problem in virtually all instances with numerous counter-measures. Tesla batteries can remain unplugged for weeks (even months), without reaching zero state of charge. Owners of Roadster 2.0 and all subsequent Tesla products can request that their vehicle alert Tesla if SOC falls to a low level. All Tesla vehicles emit various visual and audible warnings if the battery pack falls below 5 percent SOC. Tesla provides extensive maintenance recommendations as part of the customer experience.

So, that's a "yes." But there's a little more to it.

Part of Tesla's secret sauce has been turning the same batteries used in laptops and other devices into reliable and safe energy sources for a vehicle. Tesla designed the battery pack with a series of monitors that balance energy among all of the 6,831 lithium-ion cells so one doesn't set off a "thermal event" -- i.e., catch fire. But doing so requires those systems to be on constantly, which creates a drain on the system that's far greater than lithium-ion batteries typically suffer if just left alone.

Tesla downloads data about its batteries from the vehicles, and can remotely monitor their health to avoid total discharge. Yet avoiding the problem in "virtually" all instances is not the same as designing a pack that prevents it from happening in the first place. Tesla does warn throughout its owner's manual that leaving the Roadster unplugged for long periods will cause "permanent damage" -- but it never spells out that the entire pack could go bad, or that a new $40,000 pack would be on the owner's pocketbook. It has said in marketing materials that the Model S will be capable of being parked at an airport for extended stays, so it's not clear whether future models will get better technology.

And better technology already exists. Nissan spokeswoman Katherine Zachary tells Motoramic that the all-electric Nissan Leaf "will never discharge completely, thanks to an advanced battery management system designed to protect the battery from damage." Thanks to a combination of different management and battery cells custom-designed for the car, Nissan has sold 22,000 Leafs and never suffered a similar failure. Tesla's acolytes may find no fault in the charges, but other automakers know there's little margin in blaming customers for not asking the right questions.