Current flow priorities in PSU / PSU review
You may want to consider how the IC boost converters for PV panels work, such as the SPV1020 using high side switching and common grounds.  The MPPT function shunts the PV to sense voltage drop under a pulse load to detect the power available (Interrogate &amp; Observe algorithm).  Considering all the modes of operation, with monitoring &amp; protection circuits and losses is not a trivial design. You have a done a good job in your block diagram, but I agree more work still is needed to reduce the switching losses on your common ground. ( Is that a positive ground?)  Diode losses can be reduced by using higher voltage batteries and lower currents.

STMicroelectronics  SPV1020 PowerSSO-36 package for ceramic caps and 4 phase current switches.  $14 a pc. 9A max 98% eff max.



links:
 http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00275733.pdf

http://www.st.com/internet/com/SALES_AND_MARKETING_RESOURCES/MARKETING_COMMUNICATION/FLYER/flspv1020.pdf