Quick Answer
To determine a daily load for a 12V RV system, calculate the total watts of appliances and devices used over 24 hours, then multiply by a safety factor to account for peak usage. Consider the system's voltage, battery capacity, and desired runtime. This will help determine the required solar panel size and battery bank.
Understanding Appliance Loads
Start by listing all appliances and devices that will be connected to the 12V system, including lights, fans, refrigerators, and charging ports. Convert each device’s wattage rating to its 12V equivalent. For example, a 120V refrigerator might have a 12V equivalent of 10-15 amps. Consider peak usage periods and multiply the calculated wattage by a safety factor of 1.5 to 2.0 to account for simultaneous operation.
Calculating Daily Load
Add up the total wattage of all devices to determine the daily load. For example, a system with a 12V refrigerator (10-15 amps), four 12V lights (0.5 amps each), and a 12V laptop (2 amps) would have a total daily load of approximately 22-34 amps. Convert this to watts by multiplying by 12V.
Sizing Solar Panels and Battery Banks
To size the solar panel array, consider the system’s daily load, desired runtime, and available sunlight. A general rule of thumb is to size the solar panel array for 20-30% of the system’s daily load to account for battery charging and other system losses. For a system with a 34-amp daily load, a 400-600 watt solar panel array would be a suitable size. When sizing the battery bank, consider the system’s desired runtime, battery type, and depth of discharge. A 12V battery bank with a 200-300 Ah capacity would be suitable for a system with a 34-amp daily load and a 12-hour runtime.
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