2012 Prius base code P0A08

I’m have been trouble shooting the cause of this code for a month. I have a very decent code reader, it’s a xtool and I have a tech stream supplement on my laptop. I have checked all fuses, all pumps, and all other standard obvious potential issues. I was wondering if someone has gone though this and has an answer for me. The code says that the dc/dc 12 v converter is not charging the auxiliary battery but it is. I can see this on my reader. I’m getting ready to open up the top of the inverter to check connections within.
I will add that the car has significant rust and corrosion throughout. And I have cleaned and checked every wire connection I can find. I haven’t had the fuse box in the engine compartment out yet to check under it for corrosion but I have ohm’d out all fuses and everything checked out. But still am suspicious of this possibility that there is unseen corrosion under the fuse box.

the car starts and runs for about three or minutes and then produces the code P0A08

I have a feeling that I’m not the only one who has had this issue.

I will add that this issue started after an extensive repair job, body, brakes, bearings, struts all around. Then I did an extensive under coating job. All while this was happening the 12 volt battery went dead a couple of times. And I would recharge it every time. On my first trip with it after all this work was complete the warning came up that there was a hybrid battery problem. When I got to where I was going I checked the 12 v battery and it was 11.5 v. So I put a new battery in it , thinking this was the entirety of the problem, as it is stated as one of the possibilities that could cause the code but it did not fix the problem.
Any experienced Prius guy’s out there with this problem. I’m sure it’s some obscure issue that is evading detection.

Any help would be appreciated thanks.