Escapees March-April 2024

Solar panel voltage labels (12V, 24V, etc.) refer to their “nominal voltage” (i.e., in name only). Specs for panels use “optimum operating voltage” (often much higher than nominal voltage) and “optimum operating amperage” (aka current). This maximum output is a more accurate number for the sizing of the charge controller. Below are the average watts (W), volts (V), and amps (A) that one high quality solar panel can produce in optimal conditions. Remember: Watts = Volts x Amps! Series vs Parallel Con fi guration 2. Series or parallel con fi guration? Your chosen wiring scheme either increases the voltage (in series connections) or increases the amperage (in parallel connections) of the system. You need to know both these numbers in order to size a charge controller and the wire gauge, appropriately. The chart on the next page illustrates some common RV con fi gurations using vari ous panel arrays of either 100W or 200W panels (in both series and parallel), as well as the size of the RV solar charge controller you will need to safely and effectively run the system. Note: Numbers are rounded to the nearest decimal point. Solar Array Chart Series vs Parallel Con fi gurations One way to reduce higher voltage loads, as well as the size of your charge controller, is by combining your solar panel con fi guration methods. Let’s take an 800W solar array made up of 8 x 100W solar panels as an example. If you set up eight panels in series, you end up with 162V - 5A, which is beyond the voltage parameters of most charge controllers appropriate for an 800W array. But, if you set up four panels in series (yielding an output of 81V - 5A), then combine two strings of four panels in parallel, you’ll achieve an output of 81V - 10A, allowing you to use a charge controller such as the Renogy Rover 60A MPPT. This means that you can avoid the limitations of only using one con fi guration method alone. 100W panel = 20.3V x 4.93A 200W panel = 22.6V x 8.85A 320W panel = 32.7V x 9.79A

There are two types of charge controllers: 1 PWM (pulse width modulation) good for simple systems, often <200W. 2 MPPT (maximum power point tracking) ideal for systems >300W, especially if you have a large battery bank. MPPT can be up to 40% more ef fi cient! PWMvsMPPT Since a charge controller is wired in between your solar array and battery bank, it must be compatible with both sides of the wiring “equation.” Its size and compatibility depends on: 1 Total solar array wattage output 2 Solar panel wiring con fi guration (parallel vs. series) 3 Battery chemistry (lead acid or lithium iron phosphate) 4 Battery bank voltage (12V, 24V, 36V, 48V) Begin With the Solar Array Side of the Equation 1. Total solar array wattage? Multiply the number of panels you will be using times the wattage of each panel. Example: 6 x 100W panels = 600W. This total number (PV output) will help determine the size of your charge controller.

SERIES, PARALLEL AND SERIES-PARALLEL CONNECTION OF PV PANELS

PV Panels in Series

PV Panels in Parallel

PV Panels in Series-Parallel

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ESCAPEES Magazine March/April 2024