Not running like Prius-fontaine anymore! (new traction battery?)

It definitely could be, though be aware that overheating due to a clogged fan or ducting can cause the same symptoms. In either case however the battery will soon be toast if the cooling situation isn't fixed.

Just so you know, the traction battery fan doesn't blow air out of that vent, it sucks air in from the cabin interior. So there's probably no causal relationship between the rear fan running and then the cabin temperature rising. (Though there could be a causal relationship the other way around. That is, the cabin temperature rising could be the cause of the fan running, but not the effect).

 

Your loaded 12V reading of 11.5 V seems pretty low, 12V battery might be the place to start. Given that you're right up against the warranty limit, It would probably be smart to get it in to a dealer ASAP. They are more likely to be able to get at any stored codes, and even if they find nothing at least you are building up a record of the issue in case it dies conclusively just after the warranty expires.

 

Get to the dealer ASAP.
Have them recheck the 12v battery.

Otherwise, symptoms certain sound like a battery.
But the if the codes return, that will give some additional detail.

Just because they have an expensive code reader, does not mean it can read the hybrid specific codes.
If the triangle was on, obviously there are were hybrid codes in the system.

 

Yes its the Hybrid battery. Seeing alot of those with your year now. Dealer will charge one hour labor and will pull the codes reflecting that.,.
But you may be under Hybrid warranty so get to the dealer asap and spend that $125 and get in line for a new free battery!

And yes you also need a new 12 volt battery too.

 

Good outcome gtrsca.

 

You won the HV Battery Lotto! Good for you.

I'm hoping for a failure. 3yrs/20,000 miles left to go before repair/replacement comes out of my pocket.

 

Bold added by me. *gulp*

 

I feel like for the prius the more you drive it the better, and longer the trip the better. Your car may have set in the sun and it probably wasn't used for longer trips

 

Oh hey, how's the mpg now with the new battery?

 

I'd be interested to know if the dealers checked and cleaned the battery cooling fan and vents gtrsca. This issues seems to be somewhat common, especially if there are often dogs or similar pets in the car, and it greatly reduces the effectiveness of the battery cooling.

If the dealer didn't specifically mention doing this then I'd definitely look into it. There's some good info on where and what to look for in this thread here: Fur and dirt causing major battery problems | Page 2 | PriusChat

 

2005's are 9 years going on 10 years old so mileage sometimes doesn't matter that much.

If you store your car outside and continually let the interior cabin temp get extremely hot I would imagine it will greatly shorten the battery life. There's that big rear window right over the back area.

No tint no custom Prius Shop insulated front windshield shade no package rack extended to cover the battery area and always out in the sun with no window cracked =Early Hybrid battery death.

Its basic common sense. Plus your cooking all the ECU's and the MFD on the dash. The company I work for has about 150 people half of whom park outside up on top of the parking garage and no one ever even uses a window shade. Lots of Prius's. I see brand new expensive cars sitting in the sun cooking the hell out of the interior. Interior so hot you cant sit in the seat at the end of the day. I just don't get it.

You know your cooking the battery if you hear the battery fan in the backseat come on after you start the car.

 

Fortunately I've never heard that sound.