Fortunately, it's just the little 12 volt one.
As far as I can tell, it's the original battery too.
I knew it was weak when I got the car: it has thrown an error code a few times which indirectly points to a weak 12v. Also, I had to jump start it once this winter because I hadn't driven it in about 2 weeks. Resting voltage is low, too (12.5).
Of course, it's not a regular 12v battery -- it's a
special sealed Prius 12v battery that lives in the hatchback area, with a valve/overflow vent to the outside.
And it's over $200 to replace after taxes in Canuckistan.
Fortunately, it's got very close dimensions to a regular utility 12v battery (eg. lawn tractor), and some owners take that replacement route. I did that today. Capacity is going to be a bit less, and it doesn't have the overflow, but it's $65 instead of $200. I'm OK with that.
