20w coleman solar panel

Consider this: a 20w module harvesting power in the best light conditions for 5 hrs/day will put 100w back into a battery. An 1156 bulb (typical for 1975) is rated to 26W. The solar harvest will run one light bulb for less than 4 hrs. A water pump is 3-4 amps. A fan is 3 amps=36watts.

I would just carry the little module out and hook it up to the battery. When you get home, charge the battery and leave the module hooked up to the battery. Check the module when connected to battery so that it has an output diode and isn't discharging the battery.