Everything You Need to Know About Powering Your RV or Caravan

Most RVs can be hooked to a mains/shore supply. However, if you want to travel to remote places like national parks or bush camps, getting power can be a little tricky. It is very important to have a constant flow of electricity to power the lights, charge your mobile phones or laptop, and watch TV or films. But what do you do to power your RV when you have no mains power supply?

Batteries are your best option to power your RV whenever you wander into remote locations. These are very helpful for “free campers” because all electrical devices can still be used. They wire the lighting, refrigerator, and other devices directly to the battery in their RV. The battery or battery bank (multiple batteries connected to increase the available capacity) is then topped up by the battery charger when connected to mains power, running a generator or by solar panels.

However, there are still a lot of things that you should know before getting your own battery. So, read more and find out!

What Kind of Battery Should I Get?

Deep-cycle batteries are preferred for your RV as they provide sustained power over long periods of time and are designed for repeat charge and discharge. The battery system should have all the same type of batteries, either wet cell, absorbed glass mat (AGM) or gel.

RV parallel battery setups can comprise of multiple batteries in either parallel or series configuration to increase the available capacity to match the required power usage. However, battery life may be reduced if you deplete the batteries more than 50% often (refer to the manufacturer’s charging curves for the type and brand of battery you have or plan to purchase).

What Are the Things That I Should Know About Batteries and Charging?

To ensure you have adequate power for your destination, make sure your RV batteries are fully charged before you leave home or a powered campsite. Batteries are best maintained in a fully charged state for maximum life. A ‘trickle’ or ‘float’ charger is designed to do this without overcharging the batteries. The battery does this by matching the rate of charge and discharge as they are self-discharging. For RV battery banks, a more sophisticated set-up is required.

The installation of batteries should also follow the Australian Standards (AS 3011). So, only battery circuits are permitted to be installed in the battery compartment. Meanwhile, other electrical equipment like chargers and switches should be located elsewhere. It is also important that you comply with the battery manufacturer’s safety instructions. You should also ensure that your required system voltage does not exceed the product’s capacity. In addition, protective devices such as fuses, circuit breakers, and safety switches are required to meet relevant safety standards.

Important: Any electrical work or maintenance of battery chargers or inverters must be carried out by qualified personnel. If a repair is needed, always switch off any AC power supply, disconnect the battery, and let the electrician know if there is an inverter beforehand.

How Do Battery Chargers Work?

All batteries will slowly discharge over time, so a battery charger is required to recharge them. Wikipedia defines a battery charger as “a device used to put energy into a secondary cell or rechargeable battery by forcing an electric current through it”. Here are some terms that you will hear when you are shopping for batteries or battery chargers:

Boost phase – the first stage of the charging process. Essentially it is the stage where the charger puts in as much current it is capable of and as the battery storage voltage increases the charge rate decreases until the battery is about 75% full.
Absorption phase – the second stage of the charging process. This is the stage where the charge going in is reduced to about half of the ‘boost’ rate or a constant rate for several hours (unless a heavy load is drawn and it will then cycle back to the ‘boost’ stage).

Float phase – at this stage the battery charge is decreased again to about 97% of charge.
Storage phase – or ‘maintenance’ stage is where there is constant voltage to maintain the battery at full capacity whilst maintaining any DC operating loads.

Digital battery monitors can be installed to enable you to monitor the level of charge in your batteries. There are also various types of battery chargers for various types of application.

There are battery chargers designed for lead-acid batteries, sealed lead cell, and AGM gel cell batteries. The charger’s output depends on the battery manufacturer’s recommendation.
There are also time-based chargers which come with a timer, configured for a battery, and then left to charge. But these types of battery chargers still run a risk of over-charging.
Other battery chargers use a pulse width modulation or pulse technology where a DC pulse is fed into the batteries, but it is not recommended to leave AGM or Gel battery types connected to the charger for an extended period.

Some chargers supply constant DC current to the battery. However, this type often takes a long time to charge with a risk of over-charging the battery.
Smart battery chargers are designed to recharge multiple battery banks simultaneously. They are also designed to stop the charging at a certain level to avoid battery cell damage and provide good charging performance from inconsistent line voltage.

Xantrex supply a PRO and ‘Freedom’ series of inverter/chargers (in different sizes and power ranges) that is a combination of an inverter, battery charger and transfer switch in one complete system. When mains power (AC) is available it charges the house batteries and allows any surplus AC power to power other AC loads such as the microwave and TV. When the AC power is turned off, the unit inverts DC battery power into AC electric power.

Suitably rated fuses or circuit breakers must be fitted close to the battery to protect the wiring and minimise the risk of fire. When a circuit breaker is tripped, it can prevent damage from an overloaded circuit and may prevent a fire from starting.

What Is A DC-DC Charger?

DC-DC chargers can be installed to transform the output of the alternator for faster and more complete charging of the battery bank. Redarc produces a DC/DC multi-stage DC-DC battery charger that allows charging of the auxiliary battery of different chemical characteristics to the source battery, act as a dual battery isolator, and protect the start battery if the voltage is too low. Redarc also has the BMS1215S2 Battery Management System for multistage AC-DC and DC-DC designed to charge batteries to their optimal charge from either AC mains power, DC vehicle power or solar power should your RV have solar panels installed.

What Is A Generator and Should I Get Them?

Generators convert mechanical energy into electrical energy so when a generator is plugged into your RV you can run 240V (230V AC) appliances as well as the lighting. Generators can also be used to charge deep-cycle batteries if batteries have been installed in the RV. Obviously, you must have fuel to run the generator. Generators can be portable or located in built-in compartments in RVs, such as those in larger motorhomes.

The generators used for charging batteries must be capable of supplying a ‘constant’ power supply and be capable of supply for the AH size of the charger. To avoid any variation to constant power, make sure you have filled your generator with fuel before charging the batteries because as it begins to get low on fuel the output is likely to fluctuate.

The downside of using a generator is the noise, the ongoing cost of fuel and disturbing the serenity of fellow campers so please be considerate.

If you want to use a generator to run 230V AC appliances such as a microwave oven or air conditioner you may need to turn off the RV battery charger as it is likely to cause an overload on the generator unless the generator is suitably sized to run the battery charger and appliance(s) at once.

To charge a deep cycle battery in your 4WD using a generator you will need a suitable mains powered charger. Look into a 3-stage charger for this purpose.

How Long Is the Charging Time for Batteries?

The time it takes to charge a battery or batteries depends on several things:
1. the size of the battery charger
2. (CAP = capacity) – the battery capacity in amp-hours (Ah)
3. (DOD = depth of discharge in %) how deeply the battery is discharged and
4. (CC = charge current) the rated current output of the charger in amperes

A formula to get the approximate charging time may be:
CAP x DOD
CC x 80

For example:-
Xantrex’s user manual has a calculation table and let’s say you have a Xantrex TrueCharge2 40amp and one battery with a rated capacity of 120 Ah (CAP) and it is 50% discharged (DOD) then the approximate charging time with a TrueCharge2 40 would be:
120 x 50 = 1.875 or say 2 hours
40 x 80

A battery bank of say 4 batteries in parallel with the rated capacity of 120 Ah each and the battery bank is discharged 50% then the approximate charging time would be:
(4 x 120) x 50% = 7.5 hours
40 x 80

The above calculation, however, is a rough guide only as a ‘bulk’ or ‘boost’ charge will go to 75% after which the charge rate will reduce until it reaches “float” phase. This means that it could tale 12-24 hours to fully charge the battery.

Can I Charge the Battery While Driving?

Yes. As you’re driving your vehicle while towing an RV, the wiring from the tow vehicle can be linked to the RV for the vehicle to charge the RV batteries. The connection is made through heavy-duty cables that are run from the tow vehicle’s alternator to the tow bar. An Anderson plug is usually located in the tow bar as a connector. Heavy-duty wiring will also be run from the RV batteries along the ‘A’ frame or drawbar with another Anderson plug which connects to the tow vehicle.

RV three-way refrigerators (12V/LPG gas/230V AC) run on 12V power sourced from the vehicle alternator whilst the RV is under tow than on LPG gas or mains power when on site. However, running fridges through an alternator also has its limits. A tow vehicle’s standard battery does not have the voltage capacity, nor is it designed to, power the number of accessories a traveller wants such as fridges, camp lights and inverters.

The ability to charge an in-house battery in your caravan from a vehicle alternator will be limited to any spare capacity of the alternator left from what the vehicle needs to run itself. In addition to devices like portable chest refrigerator which you may have in the vehicle itself.

If you want to have this feature, you should seek specialist advice as there are a lot of factors that come into play such as a specialty alternator, the cabling, the type of battery, the type of vehicle you have, and how long you drive each day.

How Would I Know What Battery Capacity Suits My Needs?

To help you decide, you need to consider first what devices or equipment that you commonly use when travelling and calculate how much power they use over a 24-hour period. You should also factor in a 20-25% safety margin to make sure that you never run out of charge.

This calculation will assist in deciding what amount of amp hour battery bank capacity (or battery size) you require to meet your power needs. Additionally, if you have purchased the right battery capacity for your needs, it can save you a lot of money.

There are several calculators available on the web to help you calculate the minimum battery size and solar panels you require to meet your power needs and Bainbridge Technologies website has an excellent one.

Some calculators show the amount of power expressed as watts. If this is the case, divide the result by the system voltage and it will give you the current capacity in amp-hours (Ah).

For example, an estimated usage would be rough:

90 Ah battery could supply 1 amp for 90 hours, or 9 amps for 10 hours, or 5 amps for 18 hours
120 Ah battery could supply 1 amp for 120 hours, or 9 amps for about 13 hours or 5 amps for about 24 hours

An example of a calculation table of battery usage for a 12V system may be:

Vitrifrigo 230L – the refrigerator cycles. This is average Ah per day, and this could change depending on how long the compressor is running.
Little Lunar fluorescent bulb 0.75 amps x 2 LED lighting would use less power

Bora 12V fan Model 748CA – 0.19 amperes on high

So, your power requirement would be 188.35 x 2 = 376.7 Ah of battery capacity. However, you are not limited to this capacity and there are other options for you to choose from. You can always lower your power usage by reducing your usage of electric devices or using appliances which are energy efficient. Another option is to purchase a generator for your RV (See separate article on Generators).

What Causes the Voltage Drop from The Batteries to Compressor Refrigerators?

This has been a hot topic on some RV forums. Collyn Rivers, an RV enthusiast, remarked that “often 12V refrigerators were less than adequately cabled with the cable/wiring used being undersized. The confusion seems to come as a result of the Americans using AWG (American Wire Gauge) – where the higher the AWG number the thinner the conductor. Outside the USA, most appliance manufacturers use ISO ratings.”

Some RV manufacturers use a 4mm auto cable, but this has < 2 sq.mm conductor area and a 6mm auto cable has about 4.5 sq. mm conductor area. Appliance makers specify sq. mm cabling unless stated otherwise. For a maximum cable distance of two metres from the battery to the refrigerator the cable needs to be at least 6.00 sq. mm and 10 sq. mm for three metres but this will depend on the fridge current draw.

Can I Use Solar Power For My RV?

Solar power can be an initial expensive cost, but it is one of the cleanest (and quietest) forms of power. Solar panels convert photons from captured from light into electrical energy. The amount of energy captured is determined by the number of solar panels, the angle of exposure of the solar panel to the sun, and your location (determined by the latitude and the season as well as the time of day). The light energy is converted to electricity and a solar regulator regulates the charge to the deep-cycle batteries.

To maximise the energy that you will produce through your solar panels, numerous websites can help. Average daily sunshine hours map showing ‘peak sun hours’ are available from the Australian Government, Bureau of Meteorology website.

What Kind of Solar Panel Should I Get?

When looking into solar panels you will come across the term ‘photovoltaic’ (PV) cells which Wikipedia defines as “an electrical device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon”.

Solar panels are made up of cells and there are three types of cells:

monocrystalline solar cells;

polycrystalline (or multi-crystalline) solar cells; and
amorphous solar cells.

These solar cells are then physically and electrically joined and placed in a frame forming a solar panel or PV module. Several solar panels joined together is called a solar array.

Solar panels come in various sizes and capacity ranging from 5W up. To some extent, the number of solar panels and the size of the solar panels you can have or fit your RV will be based on your RV. Specifically, the dimensions of the roof, the available space after the placement, the number of roof hatches, and rooftop air conditioners.

BP Solar and Kyocera use polycrystalline or multi-crystalline cells in series for their solar panels. BP Solar states these type of solar panels charge batteries virtually in any climate.

How Do Solar Panels Work?

Solar panels are heat sensitive so that is why you see them mounted on a bracket spaced above the roof of your caravan or RV leaving some air space underneath them for cooling. Also, as the solar panels are heat sensitive, they produce less power when they get hotter particularly in the north of Australia and even around Brisbane in the summer. However, your mileage may vary. Some solar panels are less affected by shade while others will completely shut down if shaded by as little as 5%, but no solar panel will work in complete shade.

Collyn Rivers* said that ‘Outputs vary from type to type, but in typical RV installations most solar modules produce a bit over 70% of their apparently claimed output. Many modules have a small panel on their rear face that shows what they produce. For an ’80-watt’ module this is usually about 58 watts’. Collyn suggests dividing the watts by 16 or 17 (not 12V i.e.: 80W ÷ 17 = 4.7A) for a truer output.

*Reproduced by express permission, Collyn Rivers, Caravan & Motorhome Books, Broome, WA 6725. This article is protected by Copyright. www.caravanandmotorhomebooks.com

Using the example above, 22 watts is ‘lost’. Essentially the solar panel may be rated 80 watts at full sunlight at temperature but if the temperature is too hot then the voltage produced is less than the rating. There is a feature called Maximum Power Point Tracking (MPPT) used in some of the more expensive solar electric charge controllers which you could investigate further.

Essentially, it is a high-frequency DC to DC converter that takes the DC input produced by the solar panels and changes it to high-frequency AC. It then converts it back down to a different DC voltage and current to exactly ‘match’ the panels to the batteries. An MPPT is used to track the maximum power point as the sun, cloud cover, and heat build-up or cool-down of the solar panels change the output. The charge controller monitors the output of the panels and compares it to the battery charge. It also converts the output to input the maximum amps into the battery.

Recently released microprocessor-controlled MPPT models know when to adjust the output that is being sent to the battery and completes any adjustments needed.

Recent advances have also made way for the use of solar panels with lithium batteries. For example, Kedron Caravans now offer a Lithium battery option, through Enerdrive products, to reduce weight in their off-road caravans. Another brand, Kimberley Karavans also has a lithium battery option.

Once your RV is set up on-site for a few days, you may have to adjust it to get the maximum amount of energy from the sun. Particularly in the early morning and late afternoon as the panels are not perpendicular to the sun, or some shading may occur from rooftop air conditioners or trees. To fix this, you should add extra panels to compensate for this tolerance.

Portable solar power systems, including flexible solar panels, are now lightweight and convenient for camping or camper trailer use. They can be used for charging the battery back-up power for portable refrigeration and lighting. You can have it set up so the solar panel plugs into your existing solar power system of your RV. The solar panel may also come with a cable with battery alligator clips to attach to a battery for an RV or the dual battery system on the vehicle.

What Brands of Solar Panels Are the Best?

We recommended the following brands because of their features and output:

Redarc 12V Solar produces a Flexible Amorphous Blanket (FAB) with amorphous solar panels laminated onto a durable canvas backing. The solar panels (27W & 36W amorphous blankets) are glass-free, flexible, and weighs about a third of the weight of comparable size fold-up solar panel kits. The solar panels also produce energy even in low light or partial shade and fold up like a blanket for storage.
Redarc also produces 90W & 120W fold-up monocrystalline solar panel kits on a sturdy aluminum frame, fold-out legs, and stand-alone regulator to keep it away from the heat thereby making it more efficient.

Uni-Solar was a manufacturer of roll-up flexible amorphous silicon photovoltaic solar panels still available in Australia. The solar panels are made from special UV stabilised polymers making them durable. They are glass-free, flexible and lightweight. Uni-Solar panels also have shadow and high heat tolerance. One buyer reported the panel is of a plastic composition, attracts dust, and the panel surface is soft and prone to scratching.

Note: As Uni-Solar no longer manufacture these panels anymore, make enquiries to satisfy yourself they will meet your needs.

Another source of information for you to understand more about solar power for RVs is “Solar That Really Works” by Collyn Rivers. He is also the author of ‘The Camper Trailer Book’ which has information on batteries, battery charging and supplementing with solar.

A few brand names/suppliers for solar panels are BP Solar Panel, Kyocera Solar Panel, The 12V Shop, Solar Online Australia, Springers Low Voltage Specialists, Solar Xpress, and Rainbow Power Company Ltd. Some brand names/suppliers of solar regulators are Plasmatronics, Redarc, Bainbridge Technology Solutions, Outback Power Solutions, and Blue Sky Energy.

What Are Solar Regulators?

Solar charge regulators or solar charge controllers regulate or control the solar output from the solar panels into the batteries without overcharging or damaging the batteries. As the batteries are being charged, the battery terminal voltage increases and nearly all regulators use the terminal voltage to determine how fully charged a battery is.

So, the solar panels or solar modules produce the energy which is then stored in the deep-cycle batteries for use. For example, your RV is not connected to mains power and the solar panels are providing power to charge the batteries and a compressor refrigerator is drawing on the 12V power stored in the deep-cycle battery bank. If there is more power going into the batteries than that being drawn by the compressor fridge (or any other appliance running), then the batteries will slowly charge. If there is nothing to control the charging, then the batteries can be overcharged which may result in boiling batteries and corrosion of its plates. So, a charge regulator is used to control the charging current from the source thereby preventing overcharging or damaging the battery or batteries.

The best regulator is a multi-voltage regulator or one designed for use with solar panel set-ups and these solar charge regulators is a three-stage unit incorporating boost, equalise and float mode. Another type of solar regulator can also feature a low voltage disconnect (LVD) which will disconnect any load to the battery where it identifies that any continuous draw will cause permanent battery damage.

Motorhomes may have a 24 Volt, or 12 Volt battery system and you need to know what system you have before you buy a solar controller/regulator as the solar controller/regular converts the voltage into 24V or 12V.

What Is A Smart Regulator?

A smart regulator can display information such as how much charge is going in or how much charge is currently being consumed among others. For example, Plasmatronics Pty Limited has a product called Intelligent Regulators PL Series which have a comprehensive LCD display that shows battery voltage (or state of charge – SOC), input and output in amp-hours in, charge current, load current, battery temperature, performance data for the last 30 days, and an alarm feature that indicates high and low battery level.

If you decide to purchase a PL Series solar charge controller, it is also recommended that you pair it with a shunt adaptor that allows the controller to measure charge or load currents that do not go through the controller. This allows generator or inverter currents to be included in the controller’s display.

In addition, Plasmatronics states that the amp-hour reading and SOC (state of charge) will not be meaningful unless all the currents in the system are measured. The PLS2 shunt adaptor measures the current in a current shunt, converts that measurement into a digital form, and sends the data to the PL controller.

It is also a good idea to have the solar regulator or solar charge controller located where it is vented and where you can easily view the LCD display. A remote LCD display (PL Series Remote Monitor) inside your RV is also a nice touch because you do not have to go outside at night or in bad weather to read the LCD display located say in the boot of a caravan. For added protection to reduce the risk of fire a properly rated fuse should be placed between the solar panels and the regulator.

Plasmatronics now have a ‘Dingo’ series of solar regulators and controllers. The Dingo Series controllers were designed for use in travelling, camping, and marine applications but its main application is for vehicle systems. These include campervans, motorhomes, caravan, cars, trucks, and boats as it is easier for people used to working on vehicle systems to understand, due to the negative grounding.

Important: To maximize solar efficiency, solar installations are best installed by solar experts.