Will Used Salvage battery work on 2001 prius?

I purchased the guide and all was quite explicit except the vents on the opposite side is tricky to get back into the right place. My 2001 prius does run but I get the death triangle. And yes I have had to stop the car and restart it to keep moving. I don't drive it much because I hope to save it. However, I bought a used battery from salvage for $500. The salvage said it works. Don't know how long it was sitting there. However, After install The "MAIN" light along with "TRIANGLE" lights came on. The car never started. Although the ignition radio etc all works. that is probably the 12v. So I didn't want to loose charge on the original battery so I reinstalled it and the car turned on. Same triangle light only. Question is what is the problem. Is it that the main battery is too drained and some safety won't let the generator charge. Or is there some computer recognition thing for the salvage battery versus my old battery. or WHAT? - My next step is to try the individual cell replacements; but how do I know which cell is good on the salvage battery. HELP.