How important is the AGM battery (12v) in a Prius?
After driving a second-hand Prius around for seven entire years I just realized that it's supposed to have an AGM auxiliary battery. Obviously it's not the sort thing you can get on the fly so it's not that strange that the previous owner must have replaced the original with a cheap standard car 12volt. It doesn't have a gas outlet hole which is apparently required for a battery that is in the cabin.
Anyway, zero real problems running the cheap battery for seven entire years!
Until now though, but it's just old and worn out. Should I shell out for a more expensive AGM of the type specified? What do you guys think?
Prius model is 2009 (3rd Gen) standard.