P0A80 and P3000 error codes, but gas mileage still ok??

Hello! I am the second owner of a 2007 Prius with no previous accidents. It has about 103,000 miles. I've owned it for ~2 years and it has good maintenance records from before I owned it.

I've had very few problems with it until earlier this week, when (outside temperature increased to ~80) the check engine light and red triangle appeared, accompanied by the yellow brake system warning light and the VSC light. Simultaneously, the charge of the hybrid battery was suddenly down to 1 or 2 bars. I pulled over and referred the manual to help me determine whether or not I could still drive it safely home. As I drove the rest of the way home, the battery charged back up to normal levels (blue and even green) and I didn't notice the car performing any differently. Diagnostics at an experienced, trusted shop found error codes P0A80 and P3000, telling me that the HV battery needs replaced and quoting $4,000 for the part(s) and labor (likely more than the value of the car!).

I've now carefully driven it ~30 miles with the check engine light and red triangle still on, but the car's performance does not seem to be suffering - I'm still getting in the upper 40s for gas mileage and the battery seems to be charging/discharging as it has been in the past.

Does anyone know of similar scenarios where the dreaded P0A80 code appears but there is no reduced performance? I'm trying to determine how soon I should take the HV battery out (after doing more research) and start some DIY work on it such as measuring voltages and seeing which cells/modules might need replaced or "reconditioned" with a charger/discharger system of some kind.

Would cleaning the battery or battery fan make any difference?

Would purchasing a refurbished HV battery as replacement (~$800 on Ebay, includes shipping and installation?! - probably too good to be true) be something I should consider at this time?

Thanks for any help/guidance you can lend!

 

I apologize... I know this is a very tardy response - but I appreciate your input nonetheless! Due to not having much time of my own to devote to this issue, I "pressed the easy button" and paid for Green Bean Battery to come replace my failing battery with one of their refurbished ones. The lower cost plus the lifetime, transferable warranty were big selling points for me, and it's been running well ever since.