05' Prius sat for over a year...CEL and Red Triangle

Which part of the bay are you near?

You might check Hybrid battery diagnostic and repair tool for Toyota and Lexus for iOS compatibility, and if you need an OBD2 adapter read this : Hybrid battery diagnostic and repair tool for Toyota and Lexus

Many here use a "mini-vci" cable and a copy of techstream (same sofware the dealer uses) on a windows device with a USB port.

 

if you aren't getting the triangle of death, and the car is starting, the battery is probably fine. relatively speaking

 

Though possible, it may not be prudent to drive the vehicle if you plan on reusing the existing battery pack. There are a bunch of "module" RC hobby level chargers available, and another PC member will be able to offer the best direction on that purchase. Some here use the EV Peak (model CQ3), the HiTec model 44167 (the X4 AC+ model), all the way down to the IMAX mini (needs external AC source), Tenergy TB6, Turnigy Acucell 6 (or 8), or a knockoff IMAX B6AC (B6AC v2). Some hobbyists prefer chargers with an external power supply, but the choice is yours. You may also want to pay more for a charger with extra wattage, unless time is on your side

The least expensive "grid" charger option could be kludged together using LED power supplies.

The next "grid" option would be the EC-570 "Electrophoresis Power Supply" for top end balancing/charging, you can find one for around $100. There could be an even less expensive PS if you spent time reviewing the various specs for used electrophoresis power supplies, as some sell for half that price. If you do find another option, please share the make, model, and specs here for others to reference.

Many here on PC use hybrid automotive gear for grid "reconditioning", which includes a charger and discharger, it requires a harness that is specific to the hybrid vehicle model and generation. Some members here will share equipment ownership, and at times rent it out for others to use. There is a shared HA setup here in the bay area, and it should be available to loan in the near future.

Now might be a good time to tear apart the rear trim/seats so that you can gain access to the HV battery, which will also allow you to clean the HV fan at the same time. Later, once you have a usable OBD2 scanner and have recorded the DTCs (and battery health scan), you can remove the HV pack to swap in the needed module(s). Then either charge by the "module", or "grid charge" the whole pack at once.