Solar Information & Facts

Guide to solar power

Do solar panels work?
How can they help on my caravan or motorhome?
What size solar panel is required?
What different types of solar panels are available?
What other equipment is required in a solar panel system?
How easy is it to fit and wire a solar panel system?

Do solar panels work?
Yes they do!..
These are some of the most successful examples where they provide power away from a mains supply;
Communications in space,
Illuminated navigation buoys,
Irrigation pumps in remote areas,
Radio and monitoring equipment in remote areas.

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How can they help on my caravan or motorhome?
Quite simply by charging the battery(s) during daylight hours.
They work at their best in bright clear sunshine, most high quality solar panels will still produce a useful charging current even in cloudy conditions.

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What size solar panel is required on a caravan or motorhome?
To some degree this is the "How long is a piece of string" question.
As a general guide, most owners would want to try to balance the power produced by a solar panel with their average daily 12v power consumption.
Average consumption is also a wide question generally it is in the region of 10-20 Ampere hours (Ah) per day from the leisure battery.
(batteries are rated in Ampere hours, 85, 100, 110, 120 amp hours, this describes the storage capacity of the battery). A 50w solar panel will produce up to 3 Amps (A) per hour in bright sunny conditions. On a good sunny day, allowing for the changing position of the sun in the sky, low in the morning and evening, overhead in the middle of the day, you might expect this 50w panel to produce 14 to 18 Ah of battery power.
As previously stated, most solar panels will still produce power in less than ideal conditions.

The following illustration shows how much difference a solar panel would make even if it were only able to produce half of its rated maximum output.
To help increase your understanding of the flow of power from a solar panel the next illustration shows an approximate guide to current produced by a 50w solar panel during a bright summer day, from 4:00am to 9:00pm.

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What different types of solar panels are available?
There are two basic types f cells used in the manufacture of most modern general purpose solar panels, these are crystalline (monocrystalline/poly crystalline) or thin film. Both produce similar outputs in sunny conditions, although thin film cells generally perform better in overcast weather. The only down side of thin film solar panels are their size and weight, a much greater area is required to equal outputs of crystalline panels. The total range of different types on construction, shapes, sizes and outputs could become very confusing for the inexperienced. Solar panels from Germany, Spain, Japan, Croatia, Australia, America, Mexico and yes even Britain. Many of these have been tested by SOLAR SOLUTIONS and selected specially for the caravanner or motorcaravanner. As previously suggested the required output of your solar panel(s) would mainly be determined by your average 12v power consumption. There are often occasions when size and weight are important considerations, these can be accommodated from our range.

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What other equipment is required in a solar panel system?
Most solar panel systems will require a voltage regulator (controller) to protect the battery(s) from overcharging. Solar panels can produce up to 18v; this would damage a 12v battery if allowed to continue unchecked for a long period.
A regulator will allow the battery to charge at a maximum of around 1.5 to 14.0 volts, sufficient to achieve a good level or charge within the battery without causing damage. We have regulators available to cope with solar panel power outputs up to 60 amps, the smallest models is suitable for panels up to 4.5 Amps, followed by 6.5A, 10A, 12A 16A, 20A, 25A etc., on to 60A.
The battery is a vital part of any system, as with the correct selection of a solar panel, it is also wise to try to match the battery storage capacity to your average 12v power consumption and production of power from your solar panel.
It's unlikely that much 12v power will be consumed during daylight hours, therefore it is important to have enough battery capacity to store the power produced by your solar panel. This capacity should be balanced to cope with power needs in the evenings and at times of poor cloudy and overcast conditions when the solar panel output is reduced.

Most caravans/motorhomes have only one battery of around 70-90Ah, to make the best of a solar system it is a good idea to increase the battery storage capacity to a maximum of around 150Ah.
This can normally be achieved by doubling up two 75Ah batteries and wiring them in parallel (positive to positive and negative to negative). If the battery compartment is not big enough for two batteries the second one can be placed in any convenient position, e.g under a seat, in the bottom of a cupboard, safely mounted in a plastic battery box.
Monitoring equipment is entirely optional in a solar panel system, although it is helpful to be aware of the charging current flowing from the solar panel(s) and the voltage of the battery.

Our most popular ammeter and voltmeter is a combined instrument with a large liquid crystal display (LCD), a push button changes the reading from current flowing to battery voltage. Some of the regulators of 12 Amps and above are available with built-in LCD ammeter/voltmeter.
It's worth noting that when using a low output solar panel, not permanently fitted to a caravan or motorhome (left outside only when on-site), a regulator would not be necessary. You are the regulator, as you will only use the panel when you feel you need it and put it away when you don't. The time to be concerned about a solar panel causing damage to a battery, by overcharging, is when the caravan or motorhome is left parked with no 12v power being consumed, this is when a regulator must be fitted.

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How easy is it to fit and wire a solar panel system?
When you purchase a Solar Solutions solar panel system or individual system component, it will be supplied with all fitting and wiring instructions as required.
Generally, it is not too difficult to fit an average system, although to do the job properly can be quite time consuming. We can offer a fitting service for those not prepared to get involved, however for those who like to carry out their own installations, the following is a guide to the basic steps.

Determine where each of the components is to be fitted. Let's assume the solar panel will be fitted on the roof, either directly to the roof skin, to the top of a Top-Box, to the bars of a roof rack or any other ingenious position.
Wherever you decide, make sure you minimise the possibility of shadows over the panel(s) from any other equipment fitted to the roof. You must consider how/where the cable will enter the inside of the vehicle and the route of this cable to the regulator and monitoring equipment (if fitted).

Wiring. It is normally unnecessary to run new cables to the battery(s) as most vehicles have a 12v electrical control panel already fitted with a cable suitable to carry the charging current back to the battery.
The cable from the solar panel and regulator can normally be routed through cupboards. As previously mentioned, wiring diagrams are supplied with all equipment.

Fitting the solar panel. In our experience the most popular place to mount the panel(s) is directly to the roof skin. It doesn't matter what material the roof is made of, panels can always be successfully attached providing you use the correct method and fitting materials.
It is advisable to fit the panel(s) leaving a gap underneath to allow excess heat to dissipate away during very hot conditions. Surprisingly, solar panels actually lose efficiency if the cells get too hot.
As a general guide, the gap underneath needs to be 1/2 an inch or more. The following sketches show the four most popular methods of attachment.

Many owners are concerned about making holes in the roof of their caravan or motorhome in order to attach the panel(s) and passing the electrical cables into the vehicle.
We have successfully used a very reliable adhesive/sealer called SIKAFLEX 291. This product has established an excellent reputation in marine and industrial applications and is far more suitable than a silicone sealer.

Effectively you can stick the brackets or battens to the roof. We prefer to be doubly sure by also using screws or rivets through into the roof backing material, when using the ally bracket.

Method A. The SIKAFLEX 291 will ensure a good seal around the mounting fixings and also around the cable, if it enters the vehicle through the roof. If you prefer to use the adhesive/sealer only, with screws or rivets, it is advisable to use a longer mounting bracket than shown in Fig 3.

Always remember to cover any exposed cable on the roof, it should be protected from the harmful rays from the sun. White plastic conduct is very cheap from the electrical section of stores such as B&Q.
This can also be stuck down with SIKAFLEX 291.
Whenever possible, we try to pass the cable through the roof directly under the solar panel, the panel then protects the cable.


If that has caught your attention, read on...

Some of us will often choose a camp site for the convenience of using the hook-up facility. During colder months this may well be necessary, during the warmer times of the year however, a site with less facilities, or even peaceful farm site may seem more attractive.
This is where the major savings can be made, in dramatically reduced site fees and no electricity charge, BUT only if your vehicle is equipped to provide you with sufficient 12v power, without hook-up?

The solar panel systems referred to in this brochure, along with adequate battery storage capacity, would relieve the need for hook-up for most of us.