Identifying bad ePub conversions

Hey guys, I inherited a pretty enormous collection of ePub manuals for obsolete machinery from a coworker and it looks like he just converted a bunch of them blindly from pdf or just scans from hard copy dumped in an ePub wrapper, resulting in some pretty useless files for reading on small mobile devices. I'm currently sorting them manually by opening each file, largest ones first, and checking that they're broken like this or just an image heavy but proper ePub. Is there a plugin or something that will automate this process?