I have the same issue with my Aexpert. It connects to grid on 44V, but I have a Li-ion 13S, so I am losing around 20 to 40% of my capacity. My batteries have their own BMS, so I thought to put a DC-DC step up converter, so it will keep the voltage over 44V, and the BMS itself will cut the output on set voltage to keep the batteries safe.
I only found something like this in Victron Orion-Tr 48/48-8, that keeps the output voltage on 48V but the load capacity is only 8 Amps, so I need to install at least 10 units in parallel.
Does anybody know if this will work or if are alternatives with more load capacity in the market?
Hope the idea helps to find some solution to our problem.