Ultra Efficient Solar Chargers

    Solar systems add an extra dimension to your off-grid experience with the ability to charge your battery without a shore power connection. Enjoy the benefits of free solar energy.

    Boundless recommends and installs Victron Energy BlueSolar and SmartSolar charge controllers.

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    Solar Charge Controller Basics

    Solar Charge Controllers connect to solar panels at the PV connections to receive solar energy and convert voltage developed by the PV panels into voltage and current suitable for charging the battery at the output battery connections
    Solar panels for RV's are typically installed on the roof and connected in parallel to minimize sensitivity to shading.
    A positive and negative wire is run from each solar panel to a combiner box where all positives and negatives are commoned together into one positive and one negative wire for transit to the solar charge controller.
    The charge controller is installed inside the coach as close to the battery as possible
    Large gauge wiring is used to connect from the charge controller to the battery via a suitably sized breaker to minimize losses
    All of the charge controllers supplied by Boundless use ultra fast MPPT tracking to maximize power
    Connections at the charge controller are terminal connections for bare wire all cases so that the interconnect wire size can be maximized and losses minimized.

    Setting Configuration and Remote Monitoring

    Settings in the Solar Charge Controller will be configured by Boundless to suit the battery.

    The Solar Charge Controller can be monitored via (VRM) if connected to a Color Control GX or Venus GX.
    To make full use of the VRM an internet connection is required. Read more about Remote Monitoring here.

    The Reference section has more details on the following: -

    • Blue Solar or Smart Solar?
    • Understanding solar charge controller ratings
    • Matching solar charge controllers to solar panels
    • How many solar panels do I need?

    Solar Charge Controller Overview
    Charge Current

    10 - 100A


    135 - 1450W

    PV Voltage

    75 - 150V

    Battery Voltage

    12V DC

    Number of Panels

    1 - 12


    Bluetooth and VRM

    Ultra Efficient Charge Controllers with Monitoring and Control Options

    • MPPT
      MPPT: Ultra Fast Maximum Power Point Tracking

      By constantly monitoring the voltage and current output of your solar (PV) panels, MPPT technology ensures that every drop of available power is rinsed out of your panels, and harvested for storage. The advantage of this is most noticeable when the sky is partially clouded, and light intensity is constantly changing.

    • Bluetooth
      Local Bluetooth Monitoring of Solar Charge Controllers

      Remotely control and monitor the extensive features of your SmartSolar MPPT charger with built-in bluetooth by pairing it with your smartphone or other device via VictronConnect.

    • VRM
      Remote Monitoring and Control of Solar Charge Controllers

      If your installation is connected to the internet Victron Remote Management Portal (VRM) provides access to the full power of your MPPT, anytime, anywhere; both services are free to use.


    Solar Charge Controllers - Overview

    Solar Charge Controller Basics

    This page provides guidance for solar charge controllers. Also see the solar panels page for information on solar panel performance criteria.

    Boundless provides solar charge controllers by Victron Energy, main parameters are explained below for reference.

    Solar charge controllers should be selected once the number of solar panels has been determined since the maximum current capacity of the solar charge controller should be equivalent to or higher than the expected maximum system current with all panels connected and at maximum power. The steps laid out below outline how to do this.

    BlueSolar or SmartSolar?

    When comparing similar power output solar chargers, BlueSolar chargers are generally lower cost when compared to the equivalent SmartSolar chargers.

    BlueSolar chargers do not have Bluetooth built in. Select from these chargers if you will be implementing a more extensive monitoring system using a Cerbo and GX Touch, see examples of remote monitoring that is possible with system communication centers like the Color Control and Venus here.

    SmartSolar chargers have Bluetooth connectivity built in which enables setup and monitoring using VictronConnect app for iOS, Android, Mac and Windows.

    Note - a single Bluetooth VE.Direct dongle can be used to view / change settings if needed on devices with a VE.Direct port such as BMV 700 battery monitors and BlueSolar charge controllers.


    VictronConnect lets you get live status information and configure any Victron products which either have Bluetooth built-in or are connected to a VE.Direct Bluetooth Smart Dongle

    Solar Charge Controller Ratings

    Solar Charge controllers will have two numbers specified similar to 150 | 30.

    The first number is the max input voltage in V DC created by the connected solar panels
    The second number is the max output current in A provided to the battery as a result of the connected solar panels

    Note the mixture of input (PV side) and output (battery side) of the values.

    For RV applications solar panels will almost always be connected in parallel, therefore the max input voltage will typically not be a limiting factor. Solar panels in parallel will deliver the maximum voltage of a single panel and will not increase as more panels are added however the input current will be additive as more panels are added.

    Input current and the associated output current will therefore be of more interest to us. As more panels are added, the input current and therefore the output current will increase. As noted above it is important to understand the maximum number of panels to be installed and the maximum output current that will result prior to selecting a solar charge controller.

    Matching Solar Panels to a Charge Controller

    To determine the number of solar panels that can be connected to a charge controller we need to understand the performance parameters of the solar panels to be connected. The main solar panel performance criteria are described below. These values must be specified by the manufacturer for each panel sold so that panel performance can be compared and the overall system can de designed correctly including wire sizes and charge controller sizing.

    If you are interested in the technical details, the notes below provide explanation of the important solar panel parameters: -

    Voc = the maximum open circuit voltage of the panel,V
    Vmpp = voltage at maximum power, V
    Impp = current at maximum power, A
    Isc = short circuit current, A

    These values will be stated for each panel and will be at standard test conditions (STC) with a specified panel temperature, light intensity and air mass value.

    STC is generally taken as 1000 W/m2, 25 °C and 1.5 AM (air mass). 

    There will also be two temperature compensation factors specified. One is applied to Voc and one to Isc. These values are normally specified in %/degC (of either Voc or Isc). These factors are used to calculate performance of the panel at minimum cold and maximum hot conditions. Performance at the ambient extremes is important since acceptability of the panel combination attached to the charge controller will be assessed at these extremes.

    At low ambients the solar panel is assumed to be at ambient temperature. At high temperatures the panel will be much hotter than ambient. The correct panel temperature rise to use depends on the installation type. For RV's a rise of 35C is most appropriate which assumes the panel will be installed within 6" of the roof surface which results in limited natural cooling of the panels.

    One more factor to consider is that Victron solar charge controllers need a minimum voltage at the PV terminals to turn on. This value is specified on the charge controller data sheet but is normally 5V more than battery voltage. Once operating the charge controller will remain on provided the PV voltage is 1V more than the battery voltage.

    Step1 - Determine Number of Solar Panels to be Installed

    Get Started

    To determine the number of solar panels that will be installed requires two questions to be answered:-

    • How many panels do I need?
    • How many solar panels can I install?
    See below for more information.

    How many solar panels do I need?

    As a general guide, it is recommended that you install as many solar panels as practicable or at least size your wiring and charge controller to enable installation of the maximum number later. Adding a few more panels ls fairly low cost when the system is sized correctly at the outset when compared to a later full system upgrade including wiring and a larger solar charge controller.

    I have never heard an RV'er say that they wished they had installed fewer solar panels on their RV.
    Ian Skelhorne, Boundless Power Systems

    A few simple scenarios below to provide some suggestions.

    Scenario 1

    I will be regularly off grid without hookups and would like to be as self sufficient as possible with very limited use of a generator.

    Install as many panels as is practicable, consider a second site deployable system to supplement the primary system.

    Scenario 2

    I will be off grid regularly but have no problem using a generator regularly and / or often park in shady areas

    In this scenario you will be using solar mainly for basic battery maintenance charge when in transit or storage. Install a small system of 1-3 panels.

    Scenario 3

    I typically camp near power but would like to minimize power usage where possible.

    Install 4 panels up to the maximum practicable, the more panels the fewer air cooling months you will be reliant on hookups.

    How many solar panels can I install?

    The number of panels that can be installed can be determined by an inspection of the roof area of your RV.

    Smaller travel trailers may accommodate 2-3 100W panels, mid sized travel trailers 5-8 panels and larger RV's and fifth wheels can accommodate 10-12 or more panels for a very sizable system.

    We will walk through an example below to illustrate how a solar charge controller is selected and matched to a quantity of panels


    We have inspected the roof of our travel trailer and have determined that we can install 6 x 100W solar panels. We will only install 4 initially but may install up to 2 more later. We therefore need to select a solar charge controller that will have capacity for up to 6 x 100W panels.

    Step 2 - Select the Solar Charge Controller

    Match Solar Charge Controller to Panels

    Boundless will match the correct solar charge controller to the number and type of panels selected. An example is shown below to illustrate the main factors. The example below assumes 10ga wire size for connecting solar panels with a conservative one-way length of 25ft and wire size from the roof mounted combiner box to the charge controller of 2ga and a length of 10ft. Explanatory notes are provided for the options available.

    The example shows that parallel wiring may cause the charge controller to turn off in very high temperature installations. For most practical examples for panels installed on an RV, parallel wiring is the best option.

    Example - Selection of a Solar Charge Controller
    Examples of 600W system

    Lines 1 and 2 show a 100/50 charge controller connected to 6 x 100 W panels This arrangement both in parallel and combined series and parallel configuration will be power limited at cold ambient below 32F. If your RV will only be used in the southern states in summer this could be a good fit. Line 2 shows that with a combined series and parallel solar panel wiring configuration, hot ambient will not cause the charge controller to turn off.

    Lines 3 and 4
    shows a larger 150/60 charge controller with the same 6 x 100W panel connection arrangements. This combination will not be power limited even down to -25F (-32C) so would be a good selection for a system that will be used in the winter in the northern US. As with lines 1 and 2, a combined series parallel solar panel wiring configuration is recommended for very hot ambient use.

    Lines 5 and 6 shows the 150/70 charge controller with the same panels connected. This charge controller is able to accept 7 - 8 panels connected. There is no advantage with this charger over the 150/60 provided there will be more than 6 panels connected.

    You should now have a general understanding of the process to select a solar charge controller. As noted above, Boundless will help you make the right choice of charge controller to match your application.

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