Hi Martin,

Generally speaking, they don't. While battery life is an ever evolving science, Toyota's dogged insistence on sticking to older style nickel cadmium batteries is paying off. They're not as whizz-bang as the newer lithium-ion batteries, but they're rugged and they last. There are plenty of 15-year old Priuses (using the same batteries) still running happily around and Lexus will do an annual, free, checkup on the batteries to make sure that they're in good order.