What we are going to do is define a module interface that can accomodate multiple types of charging. And I think the first modules to be designed will not use buck/boost. Later on we may move to design some buck/boost options.
I looked at Tim's use of a fet to block reverse current. For small charging currents at low voltages, this could genuinely be an efficiency boost over using a diode. I'm not sure why he needs an extra fet for that job, but it's probably some confusion about the nature of mosfets that is causing me that. I looked at the specs of his transistors. One of the issues I have discovered is that VDS for mosfets is temperature dependent and apparently tends to rise with temperature. The specs I looked at for his transistors did not show VDS figures for differing temperatures. Actually it just showed single RDS ratings that I assume you are supposed to use to figure your VDS. so I doubt that the specs are telling the whole story.
Nevertheless, I'll make half an apology to those paying attention for shooting down mosfets. for 12, maybe 24 volt charging, it looks like it is not particularly hard to keep transistor voltage drop below 0.4 volts. However, for higher voltage charging, it appears that RDS has to rise because the transistors have to be different higher voltage models, and it could easily become difficult to beat a blocking diode with a mosfet when doing 48 volt charging at high current. Another reason for not apologising though is that if Tim is right, and you need an extra set of fets to act as current blocking, then that doubles your voltage loss. (ouch) Relays can simply be turned off. They don't need any reverse current blocking.
So I started a writeup describing some module interface definitions. This writeup is not finished, and is open to discussion. It is here: http://egrouphub.com/wiki/index.php/Charger_Modules I'll be looking over Tims design for clues as to how the interfaces may need adjustments, but I think I have most of the necessary details right so far.