Prius Batteries are reported to be good for 300k miles. My mom's used Prius has 100k and is fine, perfect car for a grandma who doesn't drive much. Almost no maintenence, uses hardly any gas for city driving. She has had it 8-9 Months and drives fine. Battery is good. I had it checked out by a Master certified Toyota tech before purchase. She has filled it up maybe 6 times.