Protection in Controller

You will need to supply your regulator with a voltage of: the maximum battery charge voltage PLUS the regulator dropout voltage PLUS bits'n'bobs that the regulator circuit imposes - 14.4 + 2.5 (for LM317) + a bit extra for luck = about 18 volts input minimum. Not a problem in sunlight as your panel has a Vmp of 20V.

The LM317 circuit should include an output diode per post #51 to prevent the battery back-discharging into the regulator when input voltage drops in poor insolation or at night.