I See Electromagnetic Fields!
I plan to use a 48 V battery system, as I need to store about 10 to 20 kWh of solar energy.
What is your planned usage, that makes it necessary to have any battery at all?
Batteries can hold power to be used when the grid is down, and they can hold power from PV to use instead of from grid at another time. But, most batteries cost more per kWh than utility rates, meaning you lose money rather than saving money when drawing power from a battery rather than from the grid. Some batteries (DIY LiFePO4 and off-brand or recycled batteries) do appear to be cheaper than grid power.
PV, at least if installed DIY with your own labor, costs a fraction as much per kWh as grid power (in some areas such as California.) In other parts of the country cost is similar. It can be cheaper to install PV with zero-export and waste as much as 2/3 of production, only using 1/3 of PV production when you happen to have loads. That can save money compared to just buying from grid, and also compared to storing the unused power in battery for later.