When buying any new type of technology, it’s important to read the fine print. That’s what some electric car owners are apparently finding out. Otherwise, there is a risk that you could turn your green machine into nothing more than a fancy case for a battery pack that has become a chemical-filled brick.

Any batteries lose charge when they’re just sitting. And lithium batteries, in particular, are susceptible to damage if they’re allowed to completely discharge, as any iPod, cell phone, or laptop owner can testify. If the batteries sit too long without a charge, there is the risk they won’t take a new charge.

That’s what a few Tesla Roadster owners have found, according to online reports circulating this week.

Tesla, however, reportedly had owners sign an acknowledgement that they have read the battery warnings before picking up the roadster. This model has now been discontinued and Tesla’s upcoming Model S is not on sale yet. Tesla advises that there are several measures that limit the bricking risk, according to Green Car Reports, and Roadster 2.0 and future vehicles can send alerts to the owner when the charge is getting low.

While we don’t have a Tesla in our test fleet, we do have the all-electric Nissan Leaf. The Leaf owners’ manual addresses this by explaining:
"The Li-ion battery discharges gradually if the vehicle is parked for a long time. Nissan recommends charging the Li-ion battery every 3 months using the long life mode charging method to keep the Li-ion battery in good condition. Do not leave the Li-ion battery fully discharged or with a very low charge level for a long period of time.”

Nissan also specifies conditions under which it won’t honor its standard eight-year warranty for the Leaf’s battery. According to the manual, there are four things you must not do to the Leaf’s lithium-ion battery if you want to preserve your warranty:

• Don’t expose it to temperatures over 120-degrees Fahrenheit for more than 24 hours.


• Don’t leave it for more than 14 days with the battery fully, or near-fully discharged.


• Don’t store it in temperatures below -13 degrees Fahrenheit for more than seven days.


• And don’t top it off daily, if it already has a charge of more than 98 percent.

Fail to adhere to these rules, and your electric Nissan Leaf could become a very expensive—and very large—paperweight. The battery itself costs about half the Leaf’s purchase price.

It seems these new restrictions have caught a few EV owners by surprise—and left them facing a bill of up to $40,000 to replace the battery in their Tesla Roadster. (See a related report by Wired.com.) This appears to be a rare, and even questionable, circumstance, but it does carry a fair warning. The lesson for consumers is, especially when it comes to new technology, always read the owners manual thoroughly. It’s not always easy to predict what any new limitations might be.

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