Better to use a PMMT regulator otherwise just a Buck regulator that keeps PV at 75~80% of Voc
Yes, I'm going to use a MPPT algorithm (P&O, most probably) to keep the output power at maximum. I'm using a uC to drive the buck-boost converter thus it will be easy to implement the MPPT function.
The energy of the PV below 48V is <<10% with low solar input, so there is little power transferred by boosting it, unless that little energy is important for some reason. With moderate to high solar input, PV efficiency drops if loaded down to <=48V so no gain by using a boost regulator. Just use a half bridge buck switch IC with low RdsOn.
That's why I'm building this charger in the first place. For now, I have all the PV panels directly connected to the battery bank (Vmp = 2 x 29V) but during low lights (sunrise, sunset, clouds, fog) or hot weather, the Vmp is drastically decreasing (actually, even Voc reaches 29V threshold) hence there's almost no charging current available.
For my 48V battery bank, it would have been better to use 3 panels (Voc = 75 .. 135) or 4 panels (Voc = 100 .. 180) in series. This way, I could have build a simple & efficient interleaved synchronous buck converter.
Unfortunately, I just have 8 panels (hence no 3x option) and I didn't find any suitable MOSFET for the 4x variant neither (Vds = 400V or more and an acceptable Id current and low Rdson).
In synchronous buck/boost configurations, all the switches have to be rated at the load current (plus ripple) thus it's much harder / expensive to build a higher input voltage one.
Is there any other better option?