Surprisingly getting a replacement 12V battery from Honda is also apparently a pretty good option. Somewhat higher price than Costco, I think around $150, but it has a terrific warranty, 100 months total. The first 36 months is full replacement including labor, the remaining 64 months are prorated. Costco is a 36 month warranty, I'm not positive about the terms of the Costco warranty but it says limited warranty so I am guessing that only the first year is full replacement and then prorated after that.Right on. New 500CCA Interstate battery was less than $100 at my Costco.