Newbie Help Req

Hello,
I Recently bought an 2012 Prius and got into a recurring problem. Occasionally the signs of the big yellow triangle, engine light and yellow exclamation with circle around it come on and the screen displays hybrid error msg. I have an cheap ELM clone and used it to read the codes with torque pro app and another free app. no error codes came up, so I just cleared the errors. However the lights keep coming up randomly every two days or so and I keep clearing them. I would like to add there is no decrease in cars performance one the lights come on, just the battery doesn't charge until I clear the codes.

Today after two weeks of facing the issue, I went to the Toyota dealership and asked them to check the battery. He used techstream and it showed POA80 pending error which he cleared. after it he checked hybrid battery. All the blocks were around the 15.6 mark with minor variation. he also checked the aux battery which showed around 13.4.

That means both batteries are fine? what could be the problem which results in all the lights coming on?

 

The car has run 99,000KM. It's a Japanese version. From what I have read on websites, the battery should not have failed so quickly. There is no warranty on it hence I cannot get it replaced. What are my options?
Few more questions/ update
1. Took it few more mechanics and they just used a device and their phones to read codes. It all gave the code P0A80. Meaning battery replacement.
2. Is it likely that the complete battery has failed and I need to get it replaced?
3. Is there anyway to check if it's only an block that has gone bad?
4. Can I get this battery rebuilt/ reconditioned? How long do they last?

5. Can an 2nd Gen battery be bought (since it's cheape here) and it's cells be placed/fitted in 3rd Gen?
6. Can there be any other reasons for that error? Like inverter or fan faulty?