I have had 2 PC 680s and while I loved them at first, I found that they just don't last. One lasted 6-8 months, and one lasted about 2 years max. Probably a bit less.
And none of them ever cranked that well. If the car didn't fire up right away, or you were doing a compression test, or priming an oil pump etc, they just can't cut it.
I replaced it with a Braille. It is the basic same dimensions as the 680, but it cranks like a full sized battery. I can also leave it for a long time and it still cranks the car just fine. not slow, not "yay it started" but like a full sized battery in good shape would.
it was not as cheap as the PC680, but it wasn't horrible either.
The only down side was I had to get it from a place in Winnipeg(thru the mail) so it took a week or two.