What Size Battery Do You Need For Your Caravan?

Author: Paul Napthali   Date Posted:27 June 2018 

Understanding what type of battery your caravan needs is essential before hitting the open road.

The power requirements for Caravans and RV's is increasing every year, comparing the power requirements needed in 2018 compared to say 20 years ago will be a lot different with the advancement of technology and the need for comfort and connectivity to the outside world.  Whilst the efficiency of a lot of appliances is a lot better these days with inverter technology and LED lighting becoming readily available, it is the desire to ditch the gas bottles and generators and power these things all off the battery system only that is causing the increase in power usage. This is not a bad thing, as we are now in a world where we can do this quite easily and with better renewable energy sources like Solar.

Size does matter when it comes to your caravan battery setup    

The most common Caravan Battery setup that most caravan manufacturers supply will include 2 x 120amp batteries, with 2 x 150 watt solar panels on the roof and a 40amp AC Caravan Battery Charger.  This will give you the basic convenience of running your 12 volt appliances off your battery system, and have the ability to re-charge your caravan batteries through mains 240 volt power connected to your caravan or 12volt solar panels mounted on your roof. Yes, a family will use more power than a single person or couple, although the difference when using 12volt appliances is not that great as most of the appliances need to be run regardless whether it is one person or five making this setup a good general fit for all. It is not recommended to use any less battery amp capacity or solar panel wattage in a caravan application as the performance advantage will out-weigh the cost advantage every time. Often people will upgrade their single battery, single solar panel after an inevitable inconvenient experience of no power.    

Without including the 240volt AC appliances, the average caravanner will generally not deplete their batteries with this setup during the day as the solar panels will deliver enough power through the day to power your 12volt appliances while keeping your batteries fully charged.  Even with this common setup, if you String 3 or 4 not necessarily cloudy, but rainy days together and you will be looking to top up your system by another charging source. This can be done with a Generator, Mains 240volt power or your cars alternator if you add a 40amp Enerdrive dc2dc charger to the setup. 

Calculating your caravan’s power usage

A 12V deep cycle AGM battery (by far the most preferred variety of caravan battery) is calibrated in amp-hours (ah). If you see a 100ah rating on a caravan battery, this means that the battery can theoretically provide 1amp current for 100 hours, 5amp for 20 hours and so on.  However, once we take these considerations to a practical situation, a number of constraints apply, limiting the amount of battery power actually available for use. For starters, the voltage of a caravan battery starts dipping with usage, and the lower the voltage, the less the amperage it can offer. At about 30% charge capacity, an AGM battery is typically unable to power most appliances due to low voltage. For this reason, it is not recommended to draw below 50% of the battery capacity which results in you being able to use only half the rated amperage on any given AGM battery. The setup we recommend totals 240amps, although due to the characteristics of all lead acid batteries including AGM, only 50% or 120amps is usable in the real world. This is an important factor in considering using 1 or 2 batteries in a caravan application. 

Lets look at the common caravan appliances and their approximate average amp draw for the average caravanner over a 24hour period: 

12 Volt 

1) LED Lights and battery monitoring devices - less than 0.5 amp per hour on average per day

2) Water Pumps and Tank Level monitoring - less than 0.5 amp per hour on average per day 

3) Refrigeration - Small fridges approx 1-3 amps per hour and large fridges approx 3 - 5 amps per hour on average per day

4) TV, Laptops, Music/Radio Devices and Speakers - less than 0.5 amp per hour on average per day 

5) Power outlets for charging mobile devices - less than 0.5 amp per hour on average 

240 Volt (These appliances below are not practical be powered by this AGM setup and will require alternate power source, ie generator, mains power or large 12volt lithium/inverter battery setup)  

6) Air-conditioning and heating - Approx 60 amps per hour if trying to run off 12 volt (Based on using the Dometic Harrier Inverter type Caravan Air conditioner which is the smallest amp drawing unit on the market). 

7) Microwaves, Kettles, electric frypans, hair dryers and washing machines - Approx 20 - 50 amps per hour in shorts periods on 12 volt.  

You can theoretically work out the individual wattage and amp draw of each of your appliances and the run times required to maybe increase your battery or solar panel capacity, although you can always easily add to your system later if required. We would not recommend anything less as far as a caravan setup is concerned as there is no disadvantage to extra battery storage capacity and quicker recharging through your solar panels. Think of it as a performance upgrade allowing you extra hours of run time between charges should it decide to rain for a week, and allowing you to charge quicker should you receive only half days of sun for your solar panels. 

Car Batteries vs. Caravan Batteries

In theory it is possible to use a typical lead Acid wet cell car battery to power your caravan appliances. However, a car battery is designed to be fully charged and deliver a power pack charge of energy in short bursts to crank over your engine before being quickly topped up to 100% again. This means that your car battery is designed to operate at close to 100% capacity levels for optimum efficiency and longevity.  Shortened battery life will result when discharging your battery at a deeper level continuously as in for a caravan application. 

Deep cycle caravan batteries on the other hand, commonly referred to as AGM (Absorbed Glass Matt) are your sealed type that are constructed a little differently to allow a deeper depth of discharge. This means that you will get better performance and longevity out of a deep cycle battery for caravan applications where you are drawing a lower and more consistent supply of energy. Put simply, the cost between a car Lead Acid battery and a caravan AGM battery is similar, although you will be replacing the car battery more often in a deep cycle application costing you more dollars in the long run. 

Lithium Batteries for Caravans  

                         

If you only want to use 12volt appliances in a caravan application, consider 2 x 120amp AGM batteries with 2 x 300amp solar panels to run your general 12 volt caravan appliances.  You can add AC battery chargers or DC to DC battery chargers to help re-charge your system.  

If you want to run high amp draw appliances from your battery system, consider using a more fit for purpose technology like lithium batteries for caravans that when coupled with a quality inverter, can take the hassle out of power usage restrictions on 12volt by being able to run your everyday 240volt appliances like Caravan Air Conditioners, Caravan Heaters, Hair Dryers, Caravan Washing machines and anything that requires 240volts to operate. 

If you would like to talk to a caravan industry expert in regards to caravan batteries and setups, feel free to contact us 1800 787 278 or email us at sales@caravanRVcamping.com