Inverters & Leisure Batteries

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Using an Inverter with your Caravan or Leisure Battery

Power inverters are often used by motorhomers and caravanners wanting to get off the beaten track but still take their creature comforts with them. Inverters connect to a 12V DC supply and convert it to a 230V AC output. They allow mains appliances to be run from a leisure battery or Caravan 12 volt supply.

They’re great if you’re wild camping or likely to be using sites that don’t always have a mains hook-up but they do have limitations. When buying you need to make sure you get the right inverter so that it will provide the power you need when you need it.

Read on to discover answers to these questions

Inverters come in many sizes and are rated by their power output. Camping Inverters are widely available offering from 150W to 2500W or more. To work out which one you should get, you need the total power required by all the appliances you will be using.

How much power do you use?

To get the total power figure you need to find out how much power each appliance uses. Each appliance will usually have a sticker on it which will tell you the number of Watts or Amps it uses.

If you have the number of Watts used by each appliance you can simply add the numbers to get the total power, and then make sure you get an inverter which offers more than this.

Tip: Some devices such as TVs need more power on start up so make sure your inverters ‘peak power’ rating exceeds this.

Working out Power from Amps

If you only have the current (number of Amps) for each device you need to convert this to Watts to get the total power figure. To convert the current to power on a mains appliance, multiply the number of Amps by 230.

So, for example, a heater using 5 Amps;

5 Amps × 230 Volts = 1150 Watts

The table below shows the typical power requirements for devices people commonly try to run off an inverter. However, remember to also consider how long your battery will last supplying this power. See the section below for more details.

Once you have worked out which inverter you need it’s worth checking how long your battery will last so you know you’ll have power when you need it. There’s no point taking your TV, DVD, hairdryer, George Foreman Grill and Camping Heater only to find your battery goes flat in no time.

To work out how long your battery will last you need your power figure from above and the rating of your leisure battery given in Amp hours (Ahrs).

Read on to understand how to work it out or skip the maths lesson and use the lookup table.

Current drawn from the Battery

To work out how long your battery will last you first need to work out how many Amps will be drawn from the battery using your total power figure from earlier. Divide your total power figure (number of Watts) by 10 to get Amps when run on 12V supply.

So, if your total power figure is 300 Watts, to get Amps;

300W ÷ 10 = 30A from the battery

How many hours will my Battery give me?

The capacity of your battery will be given as a number of Amp hours (Ahr) with the most common sizes being 85Ahr and 115Ahr. Divide this number by the Amps taken from the battery to get the number of hours your battery should last from a full charge.

So, for a 115 Ahr battery, with 30Amps being drawn from the battery;

Real World

On the table below you can lookup how long your battery should last for a range of powers for the 2 most common battery sizes.

However, in the reality you will never be able to charge your battery much above 90% capacity. It is also recommended not to discharge your battery below 35% to 40%. So, if you want to keep your battery healthy, you should half the times above.

From the table above you can see that for higher power requirements you can get less than an hour from your leisure battery. While other companies will sell inverters upto 2500W, this is why Camperlands don’t recommend inverters of more than 500W for most people but there are alternatives.

If you’re committed to using an inverter to power your mains devices there are a few things you can do to get more out of your battery supply.

• Split Charge Relay
  If you’re touring in a motorhome or campervan you can fit a split charge relay to recharge your battery as you drive. As long as you’re moving on every day or 2 this can keep your battery topped up. Just remember, leisure batteries charge slowly, so a short drive won’t be enough, but if you're touring this may be a good option.
• Solar Panel Chargers
  If you’re not using your appliances during the day you could fit solar panels to top up your battery.
• Battery Banks
  Your final option is to increase your battery capacity by installing a battery bank. Basically several leisure batteries together to give you more capacity and longer run time

If you want to take your home comforts with you don't think an inverter is for you, there are alternatives.

• Gas Fridges
  One of the most common things to try and power from an inverter is an electric cool box. Unfortunately these tend to drain a battery very quickly.
  
  Gas fridges (also called 3 way fridges) use very little fuel and can usually be plugged in to the 12V to cool while you're travelling, and 230V when you're on a campsite with mains hook up.
• 12 Volt appliances
  Fit LED caravan lights and use 12 volt appliances. These use much less power than mains appliances run on an inverter
• Low Wattage Appliances
  There are low Wattage versions of many electrical items such as travel irons, low Watt TVs, hair dryers and travel kettles. These use much less power than the conventional equivelant so can be run on an inverter for longer without draining the battery.