Ok, now I think I understand what you're talking about. I was breaking it down into a simple DC circuit in my brain and not thinking about the charging aspect (like i should have) which is where your scenario of taking the B+ off the battery and shorting it makes sense. That said, I still the Optifuse breaker shown above would trip in this scenario since they react to current flowing through them and break thermally. The breaker in my Ollie doesn't even have B+ and load terminals on it which is what I would expect if it were directional. I did see where there are directional breakers available but they all seem to work magnetically instead. I do agree with you that fuses are the way to go, though, and will definitely be using them when I finally get around to installing solar.