IMy prius has 612/526 code. I have 2 questions 1. Is it always the hybrid battery? Can it be something outside battery too? 2. If it is hybrid battery, I have a spare in my garage. It was pulled from a totalled prius, bought at junkyard. But it has been sitting there for about 5-6 years. Is it still usable or would it have degraded to a point of no return? If old battery is not usable, what are some tips to diagnose the 612/526? I have the pdf, but it is a bit daunting, and wanted to know if there are some common things ( I read somewhere about "goop on the bottom" that can be wiped clean) that I should look for before getting into full blown diagnostics. At the end, is it worth all this or just buy a reconditioned battery and hope it will last few years? Thanks in advance.