Understanding Camping Electrics

Maybe one of the biggest concerns with the camping community – specifically those in caravans, camper trailers or RVs is that of having enough battery power to last your stay. More and more campers are choosing to ‘free camp’, away from the hustle and bustle of established campgrounds, which in many cases take on Disneyworld appearances. So if you do wish to camp in a more natural environment you will likely find a lack of mains power. This means understanding more about your camping electrics and how to get the most out of them.

Most camping vehicles these days are equipped with mains power AC electrics (240volt or 115volt), and a separate 12 volt DC system. You do not want to mess with the mains power systems – mistakes can kill! You should find however that mains circuits are protected by an RCD circuit breaker (RCD – Residual Current Device). In basic terms this provides some protection by monitoring the current flowing through the live and neutral wires and tripping the RCD if it becomes imbalanced.

OK, so what about the 12 volt system? Well the core of this system is your battery or batteries. The battery used to power appliances in your camper is often known as an auxiliary battery. They come in different types but my preferred option is the AGM or Absorbed Glass Mat battery (see this article for more information on battery types).

The important thing is to size your battery correctly for its intended use, and in order to do that you need to audit all your 12 volt appliances and calculate what their power consumption is, and for how many hours they will be used.

First thing then is reading your battery specifications. This is usually stenciled on the battery case. The photograph on the right shows one of my batteries. It is a FullRiver AGM battery Model HGL120-12. Below the model number is the specification: 12V 120Ah/20HR. What this means is that the battery is a 12 volt one with a capacity of 120 Ampere Hours IF discharged over a 20 hour period. In other words the battery will provide 6 Amps for 20 hours before it is fully discharged. This does not mean it will deliver 60 Amps for 2 hours – it will be less than that because of battery chemistry coming into play. However you could well get more than 40 hours out of it if you only pull 3 amps from it.

Having said that, you must never fully discharge a battery if you want it to live! The rule of thumb is to discharge no lower than 50% of capacity. This will extend the life of your battery considerably. The AGM battery shown here will comfortably deliver 60 Ampere Hours without harm (actually AGM batteries can tolerate being discharged below 50% now and then). Treated properly an AGM battery should last up to 8 years (my two AGMs are still going strong after 7 years so far).

Now we know what our battery can deliver, what do we want it to deliver? Well you need to conduct an audit of all your auxiliary appliances. Proceed this way as an example. Read the power rating label on your portable TV for instance. Here’s mine at left.

You need to work out how long you want to run it for. So let’s say I am going camping for 3 days and will watch TV for 3 hours each day; battery drain will be 9 hours at 2.6 Amps, or 23.5 Ampere hours. Now do the same for your other appliances – and don’t forget the lights. You will be surprised how much power you need.

Note: If the appliance rating is given in Watts, divide this figure by the voltage to get current draw. For example 20 Watts at 12 Volts equals 20/12 or 1.7 Amps.

I keep a list of the current draw of all my auxiliary appliances which makes it easy to calculate how long I can run them for over my camping holiday.

You may find you need more than one auxiliary battery – I have two 120 Ampere hour batteries connected in parallel, so applying the 50% rule I can now draw 120 Ampere Hours from them (you can find out more about installing a dual battery system here).

Any comments or questions, please leave a comment below.

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