It is, but alas, Nissan did a poor job of programming the charging system, and weak, undercharged (12.0 volts is nearly dead) 12 volt batteries are a very common problem. You want to avoid leaving the car plugged in for hours after charging ends, because that, ironically, runs down the 12 volt battery. You also can't rely on the car to charge up the 12 volt battery whenever it gets low, because that doesn't happen with perfect reliability in all situations.