With a 48V battery, your solar panel voltage must be higher than 48 volts to produce a charge. By connecting solar panels in a series you can increase its voltage. Take 3 x 350W 24V solar panels and you get 72 volts, the ideal number for a 48V system (24V x 3 = 72V).
Previously, with 12V systems, that meant adding more panels, larger capacity charge controllers, and huge battery banks, plus all that beefy wiring. Now, many solar consumers with higher energy demands are moving away from 12V and toward 24V and 48V systems for overall cost-space-benefit.
A standard 60-cell panel puts out ~30V, and 72-cell 37.5V. A MPPT controller needs some overhead voltage above what the battery needs. Midnight Solar says +30%. A 48V battery bank will want to charge at anywhere between 50-59 volts, and for lead-acid that needs equalization, up to 64V. So, you need a panel string that is ~ 58V X 1.3X = 75.5V.
The VMPP (maximum power voltage) of the solar panel or array has to be 1.3 times more than the battery nominal voltage. 12V systems: the VOC should be 16.8 to 21.6. For hot areas the voltage ideally is 20 to 21.5V, and if it is cold, 18V. 24V systems: the VOC can be from 33.6 to 43.2, with 40 to 41V for hot locations and 36V for colder areas.
A standard 36-cell 12V solar panel has a Vmp of ~18V. A standard 60-cell panel puts out ~30V, and 72-cell 37.5V. A MPPT controller needs some overhead voltage above what the battery needs. Midnight Solar says +30%. A 48V battery bank will want to charge at anywhere between 50-59 volts, and for lead-acid that needs equalization, up to 64V.
Over 5,000 watts: 48 volts is most cost-effective and space-efficient for large residential or commercial/industrial systems with higher power needs. 7. Main Types Of Solar Batteries