I'm looking to design a variable output power supply that can do 0-30V and up to 10A. I am going to build a custom battery pack for it out of 18650 cells so I have control over the capacity and voltage. The idea was to build a battery pack and then using an adjustable Buck converter or Buck-Boost converter set the output voltage. I've never designed a power supply before but I have a good understanding of how the two topologies work, but I have one question that I can't find the answer too and that is which one would be more efficient?
Since the system is going to run on battery power in the field, extending battery life is my goal so is one better then the other or are they pretty much the same? Would I be better off building a pack with 30+ VDC and stepping it down or building a pack of the same physical size with more capacity at a lower voltage, say 12 VDC, and stepping it up when needed?