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AWS Approved Mobile Workshop

An NCC, AWS approved mobile workshop that comes to you.

Solar panel installation by Calibre Caravan Services Ltd.

By using the free and renewable energy available each day from the sun you can charge your motorhome batteries with our professionally fitted high quality German solar panel kits. We are an NCC and AWS approved workshop with 36 years technical experience with low voltage 12v systems. The installation comes with a 5 year warranty. Once fitted you will have a high performance, efficient and (almost) maintenance free battery charger/conditioner. (Note:- solar panels do need to be kept clean for maximum performance). We pride ourselves in a quality installation that is neat and tidy with no wires visible inside the habitation area and can even install a solar panel on your roof with no cables visable from above. We often run cables through existing cable runs. On the roof we will make only one hole for the cable to pass through, this will be double protected by a sealed and bonded cable entry gland. The solar panel will be bonded to the roof with the exceptionally good Sikaflex adhesive and not screwed on in any way. We run a mobile fitting service but if the weather is not in our favour, then we also have our own workshop facilities for the purpose of motorhome upgrades.


To give you an idea of how much a solar panel kit would be supplied and fitted: -

120 Watt solar panel kit to include a 120 Watt rigid panel, mounting feet, cable entry gland, Sikaflex adhesive, 4mm2 twin cable, charge controller, Fuse holder, electrical connectors etc and labour. Fitting time will be about 5 hours. Total price £465

150 Watt solar panel kit to include a 150 Watt German rigid panel, aerodynamic solar panel mounting feet (where practical), cable entry gland, Sikaflex panel adhesive, 4mm2 twin cable, high efficiency Victron MPPT charge controller, Fuse holder, electrical connectors etc and labour. Fitting time will be about 5 hours. Total price £585.

Extra costs would be: - larger or additional panel, charging the vehicle battery in addition to the leisure battery, semi flexible panel instead of rigid panel, 6mm2 cable on larger panels or to future proof your installation. There are so many other options available it may be initially best to fill out the enquiry form at the bottom of this page and from there we could have a chat about your current set up and requirements.


Solar panel frequently asked questions, FAQ

I have been asked many questions in the past regarding solar panels and batteries. Here are some of those questions with my answers: -


Will a solar panel keep my battery charged up while in storage?

Using our high efficiency 150W kit yes, we can configure your system to optimise the charge to your leisure battery and even your base vehicle battery.


Will a solar panel charge my motorhome vehicle battery?

We can set up the system to charge your vehicle battery as well as your leisure battery. You can even have 2 linked leisure batteries and a vehicle battery all charged from the one system (3 batteries in all).


Will a solar panel charge up my batteries on a cloudy day?

Yes they will, although it will take more ‘daylight’ hours for your battery to reach the same state of charge than a sunny day. On a sunny summers day your battery may be charged to 100% by 11am, a cloudy day may take until 4pm for example. On a cloudy day the voltage output from the panel may remain the same but the stronger sunlight on a full sun day excites more electrons to produce more Amperage.


Will a solar panel fit on my roof?

We can normally find space. Often a photo of your roof will be good enough to establish what size panel will fit. We keep several sizes in stock anyway.


Can I connect a solar panel direct to my battery?

You can only do that with low wattage panels of about 10 watts. You may get a small trickle charge in the summer from a 10w panel but nothing through the winter months. Modern vehicles tend to have a higher background drain on the battery due to passive systems being always on.


Will my battery over charge on a sunny day?

No. Our automated charge controller takes care of and protects your battery. Once charged it will just give a regulated float voltage to maintain the battery against inherent self discharge. Over charging can reduce battery life, cause the production of explosive Hydrogen gas and as a result deplete the electrolyte level on lead acid batteries.


Do you make holes in the roof of my motorhome?

Only one for the power cable from the panel to the charge controller. The cable entry is sealed at the entry point to the roof and there is a second boundary against water ingress with the bonded entry gland that goes over the hole. The solar panel is bonded to the roof via feet and not screwed.


Does it have to be sunny for my solar panel to work?

No. your panel will generate a charge on a cloudy day. The Amperage output will be reduced though.


Can I fit a solar panel on my dash behind my windscreen?

You can but the output will likely be reduced by 50% to 80% by being behind the glass. Most vehicles have UV blockers (photon blocker) in the glass but this is not the only reason, glass reflects a lot of UV back to space. You may gain back a little efficiency though by having the panel positioned more perpendicular to the sun though. Another thought is that in the winter there is often condensation forming on the windscreen (inside or out) or frost.


Will a solar panel keep my batteries charged while off grid?

Well, that depends on your usage. Take a look at the question below to calculate your daily usage. From here we can make a calculation to establish what size panel you may need and maybe what efficiency savings you need to make. For example, fitting LED lights and bulbs can give an 80% reduction in power usage on the lighting circuit.


How do I calculate my daily power consumption?

In short you need to add up all the 12 volt electrical stuff you use when off grid: -

Lights. 4 x 3W bulbs for 4 hours = 16WH = 1.3AH

TV (Falcon S5 22”) 4 hours at 22WH = 88WH = 7.3AH

Water pump. 2 showers at 5 min each = 10 mins. Washing pots & hands 5 mins. Total 15 mins. 10 Watts x 0.25 = 0.25AH

Truma Combi Boiler. 3 hours heating and hot water. 1.1A x 3H = 3.3AH

Laptop 45W for 3 hours = 135WH = 11.25AH

USB charge ports, 5W. 2 phones, 4 hours to charge. 8x5=40WH, 40WH/12=3.3AH

1.3AH + 7.3AH + 0.25AH + 3.3AH + 11.25AH + 3.3AH = 26.4AH* 20% = 31.68AH

Multiply by 20% for inefficiency.

So, in this example we are using 31.68AH from the battery. If it were a 110AH battery, then there is 55AH useable energy so 55/31.68 = 1.74 days off grid before your battery is in the red.

Or you need, let’s say 32AH replenished each day.

If you have a 150W solar panel that will output 8A for 5 hours then that is 40AH which does comfortably exceed your daily usage.

Or to put another way you need 4 hours of summer sunshine to recharge your battery.


Should I have a flexible or rigid solar panel?

Rigid panels are more durable, and they have better air flow around them which makes them cooler and therefore more efficient, and they will last longer than flexible ones. They are also cheaper.

Semi flexible panels are lighter and less bulky, can be bent to follow the shape of a curved roof and can be walked on (if your motorhome or camper roof is strong enough).

The question is more of application. If you want a low profile panel or only have space on a curved roof then semi flexible panels are the way to go.


Can I fit an extra solar panel on my motorhome roof?

Yes, this is no problem so long as you have the space.

If you already have a solar panel fitted, then we can upgrade your current system by adding a second solar panel and forming a mini solar array. Depending on your current configuration we may wire the panels in series or parallel, use your existing charge controller or upgrade and also we may need to upgrade your wiring, especially if the new panels are to be configured in parallel.


What is the difference between charge controllers?

The less efficient PWM (Pulse Width Modulated) charge controller effectively throws away several volts it receives from the panel. The solar panels used on motorhomes often output about 22 volts (open circuit). If you have a standard lead acid battery it will be charged at about 13.8 volts. So up to 8.2 volts are discarded because the PWM controller effectively turns off the input from the solar panel for a fraction of each second to give an average output of 13.8 volts. Also, Google ‘Duty Cycle’ which is similar.

The MPPT (Maximum Point Position Tracking) charge controller converts the surplus voltage into Amps so little energy is wasted. The MPPT controller can be 95% efficient where as the PWM controller is only 75% efficient. That’s like the difference between a 120 watt panel and a 145 Watt solar panel. When you compare size and weight between the two controllers you will conclude that the MPPT controller is more substantial.


Will my inverter work off the solar panel?

No. The solar panel will charge the batteries that power your inverter but the panel will not power the inverter direct.


What is the difference between Monocrystalline and Polycrystalline solar panels?

Monocrystalline are the panels that we fit. Each cell in the panel is made from a single silicone crystal which makes the panel smaller, more efficient and give better performance at higher temperatures.

Polycrystalline panels are cheaper, use a more sustainable manufacturing process because they are made from many silicone crystals to each cell, this gives the cell a flaked appearance. These panels are a little larger too.

Thin film amorphous solar panels are a new type of solar panel that are still in the production stage. They promise to be cheaper and more efficient with the lower winter light levels of the UK. Once refined and in mass production I’m sure they will become overall more efficient than monocrystalline, but not there yet.


Can I fit a lithium battery to my solar installation?

Yes you can, assuming your charge controller can be reconfigured to deal with the different charge requirements of a LiPo/LiFePo4 battery. Our charge controllers are configurable to all battery types.


Can I add another battery to my existing one?

Yes. There is a certain way to configure the joining of the two leisure batteries. Don’t piggy back the new battery but instead make sure the output cables to the habitation side do not come off the same battery.


What size solar panel do I need?

That depends on your usage. You will need to calculate your expected daily Amp Hour (AH) consumption. See the question on power consumption.


Can I monitor the charge going into my batteries?

The charge controller can give an accurate indication of what voltage and current is going in to the hab batteries via an LCD display (model dependant) or the Victron charge controller we use can be linked to your phone via Bluetooth. Another way is to use a Victron shunt fitted in series to the negative output of your battery. This will give you accurate voltage and amperage reports of past and current usage. It will also give a prediction of how long your batteries will last at the current state of usage. All viewable on a phone app or remote display.


I drive every day, do I need a solar panel?

Possibly not. Depends on your usage and type of batteries you have. If you have a LiPo/LiFePo4 battery you could use a high output Battery to Battery (B2B) charger that could potentially charge a 95% discharged 110AH LiPo battery in less than 2 hours (using a 60 Amp B2B charger). If you have a standard lead acid battery a less intense charge regime is needed which will take several hours, this is more suited to solar charging. A 110AH lead acid batteries will only cope with a charge rate of 11 Amps ideally – 22 Amps on occasion (but not ideal). So to charge a 50% discharged lead acid battery to 100% you would need to be driving for 5 hours. A combination of B2B charger and a solar instalation is an optimal solution for high power users.


Will my 150 Watt panel give me 150 Watt power on a sunny day?

Yes, but only if the panel were clean and it were at the equator at midday on a sunny day, no cloud, at the equinox and at a temperature of 25 Celsius (that is what is known as STC (Standard Test Conditions)). In reality, here in the UK, you will get less than the STC. You may only expect 70% to 80% of rated performance so a 150 Watt panel will give you 120 Watts.


How long will it take to charge up my 110AH battery?

Let us assume that your standard 110AH battery is a lead acid type. This means that you can only discharge it to 50% of its AH rating. That means that once you reach the critical 12.1 volts any further discharge will result in battery deterioration and lifespan will be reduced.

So we are now looking at charging a battery that is at 50% capacity and 12.1 volts and 55AH used.

To replenish the battery with 55AH that means that we need to charge it at 5.5 Amps for 10 hours, or 11 Amps for 5 hours. NOTE for lead acid batteries do not exceed a charge rate of 20% the AH rating (10% is ideal), so in our case 22A (ideally 11 Amps).

On a sunny day in summer our 150 Watt panel will output 19.5 volts under load. In this country we will never achieve 150 w but for the calculation of Ohms law, Watts divided by volts will give 7.69 Amps so that is 7.15 hours.

In reality the 150W panel will only generate 120W so 120 Watts divided by 19.5 volts equals 6.15 Amps so that is 8.9 hours.

Go for a 300 Watt panel and we cut the times in half.


Will a solar panel power my fridge?

If its an absorption type fridge then no, or at least not practically. If you have a compressor fridge then yes, indirectly. The solar panel will charge up your batteries and the fridge will use power from the batteries so the solar will just top up what the fridge takes once the batteries are fully charged. Most compressor fridges will only take about 1.5AH from the battery. On a sunny day your panel output (after the charge controller) may be 8AH, so lots of surplus. Compressor fridges, I feel, are the way forward.


Solar panel efficiency

Midday at the equator 1 kW of energy hits 1m2 of the ground. A 1m2 solar panel is about 265 Watts so there is 75% loss. In the UK a 265w panel would be about 85% efficient (150w panes gives 128W). a panel will ultimately only give 15% of what sun hits it.


Working example of finding what size panel you need.

When Calibre Caravan Services Ltd finds time we shall complete this section.


What is Off grid?

When Calibre Caravan Services Ltd finds time we shall complete this section.


After we have completed the solar panel installation, we will test your battery and advise you on its current condition. An annual check is advised to test the system, check the panel bonding, water ingress integrity. This is part of our standard annual habitation service anyway.



Don’t let your battery be the weak link in your system.

On a hab service we test the capacity and condition of your battery. Electronically tested with the latest standard equipment. Electrolyte level topped up. Clamp condition checked and security of cable in to the clamp. Charge rate from solar, 230v charger and charge rate when the engine is running. We go beyond the usual hab check and give a hab service to give you a more in depth appraisal of your 12v system. Since we feel the 12v system is of importance, check for correct rate of charge.

Here is some battery info to consider:-



Absorbent Glass Mat, Heavy duty, 5 Year life, more cycles than lead acid.

Charge rate 14.6 to 14.8v and 10 to 20% of AH rating, don't over charge with excess amperage.

Don t let voltage drop below 12.1v (50%, below 10.5v for long time will cause damage.

Charging to 13.8v will only give 85%. Fully charge at least once a month. During the brighter months a solar panel with a correctly configured charge controller may be enough to supplement the charge.

Are all sealed, maintenance free, non spill. Some can be mounted in any orientation.

13v rest voltage

Not best for trickle charging, sulphate plates

Can deal with temperature extremes better than lead acid, -10 to +40 Celsius.

Don t leave on charge, may 'dry' out and cause permanent damage. Charge once a month for 12 hours. Holds charge well.

There are a few types of AGM battery each with a slightly different SOC voltage profile.

AGM,1 300 to 350 charge cycles

AGM, 2 500 to 700 charge cycles

AGM, 3 (lead Carbon) 1200 to 2000 charge cycles

Deep cycle

Dual purpose


Refer to the battery manufacturers spec sheet for specific information on your battery.


Under load SOC

13.00v = 100%

12.75v = 90%

12.50v = 80%

12.30v = 70%

12.15v = 60%

12.05v = 50%

11.95v = 40%

11.81v = 30%

11.60v = 20%

11.51v = 10%

10.50v = 0%


Try not to let your battery get to 50% before charging. Temperature and battery age will affect the SOC voltages.


Lead Acid

Charge rate 13.8v to 14.4v at a rate of 10 to 20% of the AH rating

12.6v rest voltage. Minimum voltage 11.6v

Rugged, takes some abuse.

Excessive high charge voltage causes excess hydrogen and oxygen production (eggy smell)

Should be vented

Can be left on charge (assuming float voltage and battery condition OK), just top up electrolyte.


12.73v 100%

12.62v 90%

12.5v 80%

12.37v 70%

12.24v 60%

12.1v 50%

11.96v 40%

11.81v 30%

11.66v 20%

11.51v 10%

11.5v discharged


Enhanced flooded battery (mid range, heavy duty)

Made more heavy duty, often for stop/start but also good leisure battery.

max 14.8v, still needs venting


Gel battery

Charge rate of 14.1 to 14.4

Can be trickle charged. Recovers better from dead discharge.

Can be stored on side. Vibration proof.

Wont handle heat very well, gel dries out, although should be OK -10 to +50 celcius.

Lower self discharge rate than AGM.

More expensive than AGM.



Too slow a charge rate will cause plate sulphation

2.2v per cell is 13.2v

Number of cycles refers to charge cycles before the rating begins to reduce.

Battery capacity measured in Amp Hours

They may be rated to 100AH, for example, but only 50AH will be useable before discharged, LiPo excluded.

Battery life is calculated by the manufacturer and often given by the number of charge cycles.

DoD, Depth of Discharge, the smaller the DoD at each cycle then more healthy cycles will be available.


Lithium battery

Charge rate 14.6v

Can be left on charge, BMS looks after battery. Can be boost charged up to 50 Amps, ideally 30% of AH rating

Dont use a normal charger. A normal charger wont bulk charge until LiPo is at 20% for e.g. A normal lead acid charger will only charge to 80% due to lower charge voltage.

Minimal voltage leakage over time

Bo not trickle charge

Can use normal lead acid charger

High end batteries have electronics to stop overcharge, BMS Battery Management System.

Can have electronics to limit the amount of current discharge, so 100AH will cut out at 100AH

Can be a problem charging below 0 Celsius, Heats up when in use so if cold use then charge.

50% lighter than lead acid.

Bast stored at a partial charge (50%) to increase longevity, +ive and -ive imbalance.

Does not suffer volt drop as capacity decreases.

Ideally don't discharge past 90% (still better than std battery)

Lithium Polymer LiPo

Lithium Iron Phosphate LiFePo4 4x more life than LiPo


NCC verified leisure battery

Cat A, off grid

Cat B, motor movers

Cat C, on hook up most of time


Discharge rate, with a steady discharge rate of 5A on a 100AH battery and it will be discharged to 50% (12.1v) after 10 hours

A parasitic drain of 0.25A will discharge a battery to 12.1v after 200 hours or just over 8 days.

Note, a 100AH battery only has a usable capacity of 50AH before reaching 12v (discharged)

Battery capacity AH

This is a general guide only, I may have made mistakes in quickly compiling my thoughts in this area. Refer to your battery manufacturers and solar system manufacturers specific info.


3 stage battery charger


Max current and voltage, internal resistance in battery regulates this. 80% charged when complete


Constant voltage with reducing current. Close to fully charged when done


Reduced voltage to prevent discharging over time

More info coming soon

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Office:-  01543 732022

Mobile:- 07462 251089

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