Another in our irregular series of answering questions from readers, this one from John Q of Eugene, Oregon:
Question: I was wondering how an electric car provides heat and defrosting. Using batteries to generate the heat will drain them pretty fast. Maybe with the 2011 Chevrolet Volt, the internal combustion engine is run for heat? But what about the battery-only 2011 Nissan Leaf?
Answer: In brief, cabin warmth on cold days is provided via resistance heating, which--as you note--uses a lot of current.
However, the Chevy Volt offers heated driver and front passenger seats.And the Cold Climate package offered for the Nissan Leaf includes not only heated front seats but a heated steering wheel as well.
2011 Nissan LeafEnlarge Photo
Those items turn out to make occupants FEEL warm enough that the cabin heat may not be necessary, or can be used at lower temperatures. But simply heating seat surfaces and a steering wheel requires much less current than heating volumes of air and blowing them around the cabin.
Under some circumstances, especially if the battery pack has been cold-soaking, the Volt may switch on its engine when started until the pack has warmed up enough to be in the appropriate operating temperature range. Then it will switch off again until the pack is depleted--which is essentially how today's hybrids work.
The Leaf, of course, does not have that option. But when either car is plugged in to recharge, some energy may be diverted to keep the pack at its ideal operating range--either cooling via fans (Leaf) or liquid cooling (Volt), or heating via elements inside the pack.