Yes/No/Maybe
Yes, if the solar panel is wired directly to the battery and is produces a charging current > 1% of battery capacity. Example 1: 5 watt solar panel produces 300ma of charging current which is .3% of battery capacity - Acceptable. Example 2: 15 watt solar panel produces 1.1amp which is 1.1% and is marginal. Example 3: 30 watt solar panel produces 2.3a which is 2.3% and would require a solar charge controller to prevent "cooking" the battery. My recommendation would be to install a charge controller with the appropriate maximum charge current rating for the solar panel(s) you have installed and/or planning to install.
