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Complete Guide To Installing Solar Panels

Article by Peter Smith - Caravans Plus

This article is the second in a series, if you have not read "Calculating how big your battery needs to be." I suggest you read it first, as it explains a lot about batteries and how they should be set up. There is already a lot of information out there, but our articles are directly related to RV's and the Australian situation. The article will expain how to get more from your batteries by either supplimenting the charging with solar or going for a complete solar system.

Not everyone who reads this needs a full system, I will cover the basics first.

Different types of Solar Panels for Caravans

Glass Solar Panel

Above: Glass Solar panels have been around the longest and offer the best solution in household and commercial installations.

Semi Flexible

Above: For mobile applications the semi-flexible panels offer some advantages, but generally at a more expensive price.

Portable Solar

Above: Folding panels in both glass and flexible are very popular with Campers due mainly to the ability to move them around to catch the most sunlight.

Basic RV Solar System

A solar panel is a grouping together of individual solar cells to produce an electric current. The electric current leaves the solar panel and goes through a solar regulator then into a battery. While you can run a 12V appliance or light directly from some solar regulators, a more basic setup connects everything to the battery.

Single Panel and single battery

Above: A single panel generates around 17 to 19 volts. The solar regulator then reduces that voltage to a suitable charging voltage for your battery.

Multiple panels and batteries can be connected to a single regulator but that will be discussed later.


Solar Panels

A solar panel is made from solar cells. Different solar cells can produce a different number of watts from a given surface area. This is particularly important for the limited mounting surfaces available on a Caravan or Motorhome.

As detailed above, the cells can be bonded to glass or a semi-flexible base. The temperature of the panel surface can effect the output also. This is a reason given to support the use of raised glass panels. While I have not tested the difference in output in identical circumstances, I chose a flexible panel due to the weight reduction, durability, and ease of cleaning. The cost was only marginally more after the price of mounting brackets was added to the glass panel cost.

Fixed panels are extremely convenient and more secure from theft compared to portable panels. Portable panels allow for maximising solar capture by locating and pointing the panels directly at the sun. Theft of portable panels can be an issue particularly if leaving the campsite unattended. You also need to allow storage space for portable panels that are packed up and not operating during travel.

A panel that can be fitted to a roof during travel and only removed when setting up in a shaded position is also a real option.

The specifications of a solar panel will indicate the output voltage and output wattage. Solar panels can be joined together to give additional wattage output at the same voltage.


Solar Regulator

Remembering from above, a solar regulator controls the voltage that comes from the solar panel to what the battery needs to charge correctly.

The solar regulator will have a specification for the maximum number of amps it can accept from the solar panel(s). Adding the total number of amps from multiple connected panels will give the minimum sized regulator you need. Don't skimp on this, as many people decide to increase panel numbers or size after a while. Another reason not to cut it too fine is that solar panels can actually exceed the quoted output in ideal conditions, especially in full sunshine but cold ambient temperature.

Another important consideration is if the solar regulator can vary the output to maximise the battery charging like a multi-staged battery charger. This allows faster battery charging at the beginning and float charging to get the battery up to 100%.

Some other features that a solar regulator may have are:

  • display the incoming amps
  • display any load connected
  • prevent current returning to the panel
  • prevent battery discharge below a certain level if the load is connected to the regulator, rather than the battery
  • prevent overcharging of the battery

    Solar Panel Connectors

    Some solar panels come with MC4 connectors which allow for easy waterproof wiring. We also sell the easy to add connectors. There are adapters available that permit joining two cables to one. An easy way to add any number of panels to the one set of wires. These provide a perfect junction for testing if a fault occurs.

    Many people install solar panels by cutting the connectors off and soldering, but troubleshooting problems is easier with the connectors in place.

    Solar Panel Wiring

    The instructions that come with the solar regulator will identify the wire thickness required depending on your distances, but RV applications normally use 6mm square UV stabillised wire connecting your solar panels to a solar regulator. The same thickness wire can connect the regulator to the first battery. When connecting batteries together you are advised to use premade battery leads available through automotive parts suppliers. If you have a large inverter, say 2000w, you would also connect it with battery leads to the battery bank.


    Multiple Panels

    Many people love their first solar panel and the free power they get, so they decide to upgrade. It is an easy upgrade if you have the space.

    Multiple Solar Panels Above: 2 panels (or more) can be connected in parallel (positive to positive) resulting in the same Voltage, but double the Watts. Also 2 or more batteries can be connected together in parallel to double the storage capacity. Having 2 or more batteries allows larger inverters to provide 240V for equipment like microwaves.

    An example installation may have 4 x 100 watt panels, that produce (4 x 5.5) 22 amps. This is within the capability of a 30amp regulator and will give a healthy charge to your battery bank.


    Full Solar System with Inverter

    Full Solar System with Inverter

    Above: This diagram represents a more comprehensive 12volt/240V system that is very functional and would meet the requirements of most Caravans and Motorhomes.

    a) A battery charger will be used to charge your battery(s) when 240volts are available.
    b) A multi-stage charger is best, plus the higher the Amperage output of the charger, the faster it will recharge.
    c) When the sun shines, the solar panels will feed a current to the solar regulator.
    d) The solar regulator will first try and supply current to any 12volt devices (f) connected directly to it.
    e) Any excess current from the solar panels will go to the batteries to recharge them. The batteries can accept charge from a battery charger and a solar regulator at the same time.
    f) While 12volt lights and devices could be connected directly to the batteries, the better solar regulators will prevent over-discharge of your batteries if you connect the devices to the 12volt load terminals provided on the regulator.
    g) Most installations will now include an inverter, which generally gets connected directly to the batteries. The inverter produces 240V that you can connect any **240v appliance to.

    **Warning: Do not connect your battery charger to this 240v outlet. Specialised switching is required to input the 240v back into your 240v circuit.


    For more information on how many panels and how many batteries you need, see "Calculating how big your battery needs to be."

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  • 16 Comments

    • comment-avatar

      Rod

      Well presented good valid information

    • comment-avatar

      Terry

      solar panel 200w out put 19.95 v it is going through 12 dcdc charger is this right thing to do?

    • comment-avatar

      ShedMan™

      Awesome info here but could you please explain if the solar panel to regulator should be fused to prevent damage in the unfortunate event of a short circuit, Also should the output from regulator to battery/s be fused?

    • comment-avatar

      Christina

      Very informative. The diagrams also help explain it more.

    • comment-avatar

      Jim

      Aux and battery low wiring

    • comment-avatar

      Simom

      Can I then run a power lead from the inverter into the 240v input on the caravan so my whole van is powered?

    • comment-avatar

      Smitty

      Safety and legal wise I have no idea . But I do know it works and works great . Been doing it for years . My inverter has a kill switch though .

    • comment-avatar

      dennis lourigan

      I found the info very helpful, plus the diagrams, good on you

    • comment-avatar

      Graham

      No mention of MPPT solar controllers and their greater efficiency over PWM type. Also MPPT controllers are far superior if panels are connected in SERIES. Greater input voltage reduces need for heavy wiring with lower voltage loss over longer leads too. More sophisticted in operation for a greater output. Unfortunately somewhat more expensive.

    • comment-avatar

      Leon

      I have 2 200 watt panels volts going up to 17 volts what regulators do I need

    • comment-avatar

      Stephen Hope

      2x200W=400W Max Voltage stated = 17Volt W/V=A therefore 400/17= 23.5Amps but to be safe 400W/12V=33.33Amps so a regulator capable of 35Amps would be more than sufficient to handle the power of your system.

    • comment-avatar

      Ian

      I'd like to add an extra solar panel to the roof of my van. Due to best mounting position & way of routing wire from extra panel to the existing solar regulator (TPS1230), wiring would need to be approximately 8 metres long. will this cause a problem with voltage drop. Should I install another solar regulator closer to the new solar panel. Both solar panels will be charging the same battery.

    • comment-avatar

      dj wizard

      suitable directions

    • comment-avatar

      Rodney

      Very informative just what i wanted to read Thank You

    • comment-avatar

      Geert

      In most diagrams their is no earthing to chassis just like the above ("Full Solar System with Inverter") is that fine or do you need to earth just the AC or DC or Both to chassis

    • comment-avatar

      John

      Very good info. I'm wondering if I have a dodgy cell; I connected my cell as per your simple setup. I turned the fridge on to battery to check cell output. 19V at the regulator terminals which dropped to 12v with fridge on. . The fridge draws 13 amps. The battery was measured as suppling 12 amps, the cell to battery 0.6 amp. Any ideas?

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