Pretty sure my 12v bat is dying. Can anyone confirm before I order a new one?

No need to get confirmation, a 2009 battery is at least 6 years old. Time for replacement.

Amazon sells the optima battery for $147.xx

 

Sounds about right - I've been browing various threads about 12V batteries and how to diagnose when they're about to die. There's a way of getting the diagnostics screen to come up on the Mult-Function-Display, and I'll let you enjoy yourself hunting for that. The other method involves use of a MultiMeter, and the ability to operate it - I've no idea if you have that skill (or access to a meter?) I notice that you're only 30 mins north of me (Nashua, NH) so I concur that as the nights have been cooling off, and this very morning I swapped to the winter wheels (see other threads), and shortly I'll be using the garage instead of leaving the car out in the elements. My car is the same age as yours, and has 105,000 miles on the odometer, so I was wondering how many miles on yours? …and so I might be condsidering a replacement in the not-too-distant future, in which case I think I might go here: http://www.batterymart.com/p-9a51p-agm-prius-auxiliary-battery.html?Category_Code=toyota-prius-smartkey-system-battery - Cheers - Wil

BTW Welcome to PriusChat! …lots of enthusiastic folk, and all the information you'll ever need to get the best out of your Prius (PS: We all would like to see plenty of pics of your Prius)

 

Cold weather/age, all point to a bad battery.

There are lots of posts/threads on this site as WilDavis said and the multimeter check is what I used to diagnose my battery. I had a meter, but had no idea how to use it. A few simple pointers from PriusChat member UART solved that problem.

I used the jumper spot in the fuse box and a negative ground on the frame to check my 12V. Anyway, you don't need that elearnaid kit, as there are a number of aftermarket batteries that now fit the Prius.

I will be the lone voice though and lobby for a genuine Toyota battery from the dealer. A little pricey, sure, but if you hunt on the dealership web sites, etc., you can probably find a discount coupon. The big plus with the Toy battery is you know it will fit with no modification necessary.

From your questions, you sound as if you were in the same spot I was when I had to change my battery. Did not know much about it, but wanted to do it myself. The Toyota battery made that easy and they have a pretty impressive warranty, including free roadside service, installation during the initial two years and after that free replacement period, their pro-rata is not even that bad.

 

The Toyota batter is the cheapest Toyota could source it for, just like the shocks, get something better. The optima is an exact oem fit, the price is much less than the Toyota and money is money.

 

I would check the Optima's most recent "reviews" on this forum before recommending it.

I do think there are other options, Deka, the Marathon mentioned, which I think I read is made by Deka....Exide....so yes, there are other options than Optima or Toyota that seem to have the EXACT fit.

But, I haven't seen a better warranty than Toyota's. And, most towns of any size have a nearby dealership.

 

I think the Toyota battery is not the cheapest they could source, it's the best battery on the market. The reason I recommended the Optima on my previous post, it's because the OP wanted the best deal.

 

do you have a batteries plus store in the area?