Gen 1 2003 Prius Hybrid Battery Problems

I got a 2003 gen one in Feb 2024 with 77k miles on it and garage kept. It was nice. Previous owner had every receipt for every piece of maintenance and repairs done including a remanufactured hybrid battery in October 2022.

a few months after I got it, the triangle of death light came on. I checked the code and it was P3001 Battery ECU. After a little bit the lights went away in its own. A few months later, it happened again. I went to EBay for a new battery ECU and after installing realized I replaced my 89890-47030 with a 89890-47060. Went to Facebook and people said it would be fine.

A few months later the code came back, and went away once again. This now happens every few months. I’ve noticed it seems to happen if the car sits for 5 days or more, or if I’m only taking it on very short trips. I don’t notice any issues with the way the car runs. MPG is the same, and everything seems to work as usual. I just keep getting code P3000-123 Battery Control System, and code P3001 Battery ECU.

Is it possible that I installed another battery ECU that is also bad. Or is there something obvious that I am missing? Dealer wants $200 to diagnose it, but I fear they will just pull the codes and tell me what I already know. They also said it won’t be under warranty because the battery was an after market reman and not a Toyota battery so it’s a 1 year not 3 year warranty.

Does anyone have any insight on where I should start? Should I put another eBay computer in it? Should I pay the dealer to diagnose? What do yall think? Thank you!!