RV Solar Panel Reference

Compact High Efficiency Solar Panels

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 and feel good about using a renewable energy source on the road.

Boundless recommends and installs Renogy and ZAMP solar panels that have been used extensively in various applications including mobile installations for more than 10 years.

Solar Panel Features - Efficient, Durable Panels for Mobile Applications

Monocrystalline Panels - More Efficient

Boundless installs Monocrystalline panels. Monocrystalline panels use high-efficiency cells that help increase module efficiency which is important where panel surface area is limited due to roof space, maximizing output is key. Typical cell efficiency for Monocrystalline panels is between 22% and 21%. Polycrystalline panels have a typical cell efficiency of approximately, 18.5%.
Bypass diodes minimize power drop caused by shade and ensure excellent performance in low-light environments.

Reliable

Advanced encapsulation material with multi-layered sheet laminations enhance cell performance and provide a long service life. EL tested solar modules; no hot-spot heating guaranteed. TPT back sheet ensures smooth performance over a long period of time.

Durable

Guaranteed positive output tolerance (0-3%); withstands high winds (2400Pa) and snow loads (5400Pa). Corrosion-resistant aluminum frame for extended outdoor use, allowing the panels to last for decades. Anti-reflective, high transparency, low iron-tempered glass with enhanced stiffness and impact resistance. IP65 rated junction box provides complete protection against environmental particles and low pressure water jets.

Solar Panel Installation Basics

A positive and negative wire is run from each solar panel to a roof top mounted combiner box where all positives and negative wires are commoned together via terminal strips to enable one larger positive and one negative wire for connection to the solar charge controller.
The charge controller is installed inside the coach as close to the battery as possible. See more details about solar charge controllers here.
Properly sized wiring must be used to connect from solar panels to the combiner box and then from the combiner box to the solar charge controller to minimize losses.
Wiring connections at solar panels are MC4 connectors which are industry standard for solar panel wiring. Boundless uses large 10ga PV wire to connect from the panels to the combiner box. This is larger than the typical 12ga wire to minimize losses.
Connections at the combiner box are via weather proof cable glands and a terminal strip to enable quick customization of cable lengths to suit the installation.
Connections from the roof top mounted combiner box to the solar charge controller are via a terminal strip at the combiner box and terminals at the charge controller. Guidance on pairing solar panels with charge controllers is available on the Solar Charge Controller page in the Reference section.
Guidance on parallel or series wiring of solar panels is provided below.

Extend Off-grid Stays with Solar

Silently charge your battery. One to two panels for battery maintenance and four plus panels for substantial charge capability suitable for RV's and travel trailers with larger demands. An essential addition for your next off-grid trip.

See the Reference section has more details on the following: -

Solar Panel Performance Criteria
Should I Use Parallel or Series Connection?
Matching solar charge controllers to solar panels
How many solar panels do I need?

Solar Panel Overview

Power

100W

Efficiency

21-22%

Voltage, Vmp

17.7 - 18.9V

Current, Imp

5.29 - 5.70A

Connection

MC4

Weight

15.0 - 16.5lb

Full Range of Panel Sizes Available

Boundless will generally use the largest panels that will fit. 100W panels are typically used for Airstream travel trailers and smaller RV's, 200W panels generally fit well on larger RV's. 320W + panels can be used for larger solar arrays as needed.

Compact and Lightweight Solar Panels that are Ideal for Mobile Applications

High Efficiency Compact Panel Options for Challenging Applications

The Eclipse panel is a high efficiency monocrystalline rigid panel with 100W power in a compact lightweight frame ideal for RV or travel trailer roofs where space is at a premium.
Rigid Frame Panels for Durability

Rigid frame solar panels are more durable and resistant to snow, wind rain and impact loads than flexible panels. Boundless offers two specifications to suit various applications.
Rooftop Installation with MC4 Weatherproof Connectors

Junction boxes and wiring with pre-terminated MC4 connectors for reliable long term connections and easy disconnection for removal. Rooftop combiner box is provided to enable multiple panels to be combined.

Solar Panels

Solar Panel Basics

Solar panels convert light energy to electrical energy and when connected to a solar charge controller can be used to charge a battery.
Solar panels for RV's are typically installed on the roof and connected in parallel to minimize sensitivity to shading (see further details below).
A positive and negative wire is run from each solar panel to a roof top mounted combiner box where all positives and negative wires are commoned together via terminal strips to enable one positive and one negative wire for connection to the solar charge controller.
The charge controller is installed inside the coach as close to the battery as possible. See more details about solar charge controllers here.
Properly sized wiring must be used to connect from solar panels to the combiner box and then from the combiner box to the solar charge controller to minimize losses.
Wiring connections at solar panels are MC4 connectors which are industry standard for solar panel wiring.
Connections at the combiner box are via weather proof cable glands and a terminal strip to enable quick customization of cable lengths to suit the installation.
Connections from the roof top mounted combiner box to the solar charge controller are via a terminal strip and weather proof gland at the combiner box and MC4 or terminal at the charge controller. Smaller charge controllers will generally be terminal type, larger versions have an option for MC4 connectors.
Guidance on pairing solar panels with charge controllers is available on the Solar Charge Controller page.
Guidance on parallel or series wiring of solar panels is provided below.

Understanding Solar Panel Performance

Solar Panel Parameters

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. Boundless sells two types of solar panels currently as shown below.

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.

Solar Panel Wiring

Parallel and Series Connection

Solar panels similar to batteries can be wired in parallel or series. The same rules regarding voltage and current apply to solar panels: -

If 2 panels that generate 20V and 5A are connected in either series or parallel the resultant voltage and current will be as follows: -

For series connection:-

Voltage = 2 x 20V = 40V
Current = 5A

For parallel connection:-

Voltage = 20V
Current = 2 x 5A = 10A

For 6 panels all connected in parallel:-

Voltage = 20V
Current = 6 x 5A = 30A

For 6 panels connected 2 in series and these 3 strings in parallel:-

For each series string:-
Voltage = 2 x 20V = 40V
Current = 5A

When these 3 series strings are connected in parallel the resultant overall values are:-
Voltage = 40V
Current = 3 x 5A = 15A

When to use Parallel or Series Connection

In general for RV's and travel trailers parallel connection of solar panels will be the best approach. Parallel connection of panels will ensure each panel if shaded will not limit output of any other panel. This arrangement is therefore best for most RV applications that will see variable shading across the roof of the RV at times.

A combination of series and parallel connection is recommended where the main use of the solar system will be in extremely high ambients (above 95F) and full sun conditions is the norm. In this type of installation, PV voltage may drop as ambient and panel temperatures rise to the point where there is not sufficient differential between PV voltage and battery voltage and the charge controller may turn off. Note that Victron charge controllers require a minimum differential between PV voltage and battery voltage of 5V for the charge controller to switch on and a differential of 1V for the charge controller to continue to run. Lithium batteries including those supplied by Boundless will be fully charged at around 14.2V so it is entirely possible for PV voltage to drop below this 1V differential at higher ambients. In this case a combined series parallel wiring arrangement is recommended since the PV voltage of each panel is additive when panels are in series.

An example of both wiring arrangement is shown below in the drop down boxes.

For worked examples of solar charge controller matching to solar panels and more discussion on high and low temperature effects on solar panel performance, take a look at the section on Matching Solar Panels to a Charge Controller on the Solar Charge Controller page.

Solar Panel Parallel Wiring

Parallel connection of solar panels as shown above is preferred in most installations and ensures best performance in partial shade conditions.

Solar Panel Series / Parallel Wiring

For installations that will be used predominantly in full sun, with limited shade, and very high ambients above approximately 95F, a combination of series and parallel connection as shown above is recommended to ensure minimum voltage of the panel array at maximum ambient is at least 1V above battery voltage. Solar charge controller will turn off if PV voltage is not at least 1V above battery voltage. Boundless lithium batteries are fully charged at 14.2V so this is entirely possible for some panel combinations and southern US locations.

High Efficiency Monocrystalline Panels | Rigid Aluminum Frames for Durability | Compact Footprint to Enable High Power Density even in Challenging installations

High Efficiency Monocrystalline Panels | Rigid Aluminum Frames for Durability | Compact Footprint