The Remington Solar Attic Fan 25 - Watt does not hold a charge. The fan is activated when it is receiving at least 7 watts of power from sunlight and when the temperature is at least 82 degrees.
Per the manufacturer of the Remington Solar Attic Fan 25 - Watt: All our fans come with a factory preset thermostat/humidistat combo. The fan only turns on when attic temp reaches 80 degrees or the humidity is above 75%. Animal guards will keep small birds out.