Is it my 12v or my Hybrid battery?

Hello there,

I have a 2008 Prius, 180,000 miles. Car was working fine, and 2 days ago I start it up and I get the red triangle, check engine, vsc, and ((!)) lights on. Turned it off and left it, and went back today to see what's going on. Turned it on again, same lights, and I decide to try to drive it. I drive it up the road to O'Reilly's to get the check engine read. Its driving fine there and back. The reader brings back the code "P0AFA Hybrid/EV Battery System Voltage Low". I call up the dealership and they said its likely the hybrid battery needs to be replaced, quoting $4,000. After looking around online, i decided to just check the 12v. I view the vehicle signal check on the dashboard and it reads 11.5v. When I turn the car on and drive it, it reads 14.1v. I drive it back up to O'Reilly's to test the 12v and they said it looks like the 12v is good but its drained and needs to be charged. I drive it around the neighborhood for a bit to try to charge it. I check the vehicle signal check in the dashboard again and it reads 12.2v but then drops to 11.8v in about 5sec, dashboard lights are all still on. So now I'm wondering if its the 12v instead of the hybrid. Since its reading under 12v at rest, is it more likely that its the 12v and not the hybrid?

Note1: I had the 12v replaced by AAA a little under 2 years ago. I've only just now seen some posts on here that they have shit batteries.

Note 2: I have a Bluetooth OBDII reader coming tomorrow and plan to look at the hybrid battery through the Dr Prius app, but not sure if that will actually help me diagnose the problem since its my first time trying that out.

Thanks in advance for any help

 

That's a bummer to hear. I got my obdII monitor and ran it in the Dr Prius app. Below are some photos of what it looks like. It does look like the hybrid battery is going unfortunately. Sad times =(

 

Actually, after looking a little deeper on here, i stumbled upon some posts that had negative voltage results like mine in the Dr Prius app. It appears that a negative voltage reading means there is a failure in the voltage sensor harness or there is corrosion on the pins in the ecu socket (inside the HV battery) where that harness plugs into. Does that sound reasonable to you and maybe that could be the culprit instead of the HV Battery itself going bad? I've attached a picture of what the reading says at first before the bars go negative.