Amazon has the Optima 12v Battery DS46B24R On sale $147.05

This item does not qualify for the Prime 2 day shipping, but you may still get it within 2 days. It's normally shipped ground only.

It's a good price but with my experience, I would probably stick with the original manufactured battery from Japan. It lasted you since 06 and you most likely won't be able to beat that with the Optima. I bought mine in Dec 2013 and just got a return authorization to replace it under warranty because it wouldn't hold a charge, kept reading 11.9 volts without a load.

Not everybody will have the experience that I've had with the Optima, but I read more people with Optima problems than with OEM battery problems.

Also I read from another member the OEM battery is larger in capacity than the Optima. OEM larger battery being 45 AH and the Optima 38 AH. It's not the same, although it will fit the same.

Just my 2 cents.

 

It is true that the Optima battery mentioned in this string has a amp hour rating of 38 whereas the OEM Yuasa battery that is for the Prius equipped with the SKS system and other options or packages (minimum package #2) has a amp hour rating of 46. This information can be found by searching the internet and reading the manufacturers specifications of said batteries.

http://www.optimabatteries.com/en-us/shop/yellowtop/optima-batteries-ds46b24r-yellowtop-prius-auxiliary-battery/

http://www.yuasaeurope.com/images/uploads/uk/downloads/YBSU25446_Yuasa_Cat_09_cars__light_vans_complete.pdf

When reading the pdf file above for Yuasa, go to page #6 of the file and look at the "OEM JIS Specialist Range". Look closely at the batteries for Gen II as there are two different batteries. S46B24R clearly calls out 46 amp hours.

When reading the website from Optima, study the spec column on that page. You will see it is clearly called out 38 amp hours.
For the base Prius Gen II (no SKS) a smaller battery was used. That battery has a 35 amp hour rating. Also note that the Gen I Prius had a 35 amp hour battery however the post configuration is different.

I also recall that Kris (cyberpriusII) recently purchased one of the OEM batteries that is currently being sold by Toyota.

You can plainly see the amp hour rating which shows 45.

Not sure if they are 45 or 46, but still slightly more amp/hr than the Optima.