PREVIOUS: RV Electrical System: Batteries & Solar Panels

Sizing

Sizing the electrical system in your RV means choosing the different components and making sure they work well together, while their relationship in terms of quantity, size and number is well proportioned.
Setting up solar is fairly simple, yet involves many interdependent parts and unless done correctly, will heavily influence the final setup. There is a certain order to the chaos:

1. Sizing solar always starts with establishing demand. This is partly an exact science (add amps from appliances), partly guesswork (how often do you use lights, heater, etc.). But try first to minimize demand by replacing old incandescent or even fluorescent lights with highly efficient LED lights.

   Eliminate high demand appliances, like a microwave, if at all possible. Download the spreadsheet for a comprehensive calculation.

2. After tallying your average daily amperage use, the number of batteries required to support the overall system is determined. Many factors influence this number:
   • Campground use
     Boondockers depend on greater off-grid use, then those that visit campgrounds on a regular basis.
   • An extensive battery bank for your RV is only recommended when your recreational vehicle is used regularly on extended trip or as a full-time home.
   • Lithium or lead-acid (flooded or AGM) batteries.
     Each has very different storage capabilities and weight requirements.
   • Temperature
     Primary use of your RV in colder or warmer climates, substantially influences the (dis)charging capabilities of your batteries. They are sensitive to temperature extremes: warmer batteries are able to release more energy than cold ones.
   • Battery rating or size.
3. Only then decide on the type of solar panels:
   • Rigid or Semi-Flexible panels (stealthiness).
   • Adjust your calculated number of panels to the available roof space, plus any used as portable units.
   • Higher voltage output increases efficiency.
   • Best overall efficiency. Solar panels currently should have an efficiency of over 20%.
4. At this time decide on your peripherals like inverter, converter, charger, controller, monitor, etc. Each should be customized for the specific system. Controllers especially, should be evaluated carefully if you decide to go with Lithium batteries.
5. Calculate amount and size of the needed wiring and buy quality connectors. This is an important step that will determine the overall performance of your system. Use a 12V wire Voltage Drop table to establish wire sizes for specific lengths with a voltage drop of less than 2%.

The entire process of defining your electrical setup, is best handled within a simple spreadsheet, that I have included.

Download the RV Electrical System Sizing Spreadsheet

With the new cargo van purchase approaching, it’s time to assess my own future energy needs and appropriately size it to the correct solar equipment for my van.

UPCOMING: RV Electrical System: My Own Setup