This will depend on your panel wattage, your battery watt-hour (Wh) capacity (a measurement of storage capacity) and the weather. A 150 Wh battery will charge faster than a 500 Wh battery because the 500 Wh battery has more storage capacity, therefore requiring more time to fully charge. In addition, a 100-watt panel will charge a battery faster than a 50-watt panel exposed to the same amount of sunlight.
Charging time will be affected by weather, shade, time-of-day, age and use of battery, efficiency of the charge controller, placement of the solar panels, and other operational factors. Be sure to look on your solar-compatible battery for an estimate of charging times as well as panel-wattage compatibility, and always check the charging characteristics of the battery to ensure it’s compatible with the wattage of the panel.
For higher battery capacity (greater than 150 Wh) we recommend using a 100-watt panel. Before doing this, however, please ensure that the battery you are charging is compatible with this wattage and use a compatible charge controller.