For a 48V 13s lithium battery pack, aiming for a voltage range between 48V to 54V should be solid. 12V is for toys and RV's, while any serious solar system for home application will be 48V or higher. Most better panels are rated to 600-1, 000 Volts in strings, so driving voltage well above 48 Volts. Solar batteries are typically 12V, 24V, or 48V, with a fully charged 12V battery reading between 12. In series, multiple cells increase voltage (e. 8V (4-cell) pack powers an RV's LED. After adjusting for efficiency losses (~90%), you'll need about 400 watts of solar panels. 8 peak sun hours (or, realistically, in little more than 2 days, if we presume an average of 5 peak sun hours per day).