If you’re new to caravanning, you may not realise that space heating, water heating and refrigeration are all designed to be run on gas as well as mains electricity. Indeed they’re sometimes more effective when they are. Most other caravan and motorhome electrical equipment runs off 12 volts and so can be powered from the on board battery when there is no mains hook up. Making that battery last is all about using its power as efficiently and economically as possible and, if necessary, finding additional sources of 12 volt power.

For outings of 2-3 days with a good, charged battery, no additional sources of power should be necessary, even if a 12 volt TV is on for 1-2 hours per day. Beyond this additional power sources may be needed. First though it’s important to understand how much power is consumed by the various 12 volt appliances. As you will see from the table some use a lot more power than others. Power is measured in watts - the more the power the greater the watts.

Item
Typical Power consumed (watts)
17” LCD colour TV
35 - 50
15 “ LCD colour TV
25 - 40
19" LED colour TV
25-35
Satellite receiver / Freeview box
12
TV booster
0.6
Halogen downlighter
10 or  20 (depends on bulb)
Fan for blown air heating
10 – 25 (depends on speed setting)
Fluorescent strip light
6 - 7
LED strip light
2 - 3
LED spotlight
2 – 3
Submersible Water pump
25
Diaphragm Water pump
50 - 60
Alde wet heating (on gas)
5
Caravan mover
See text

From the table you can see that modern flat panel TV's are quite economical and that tthe newer LED backlit ones are even more efficient.Do make sure that the one you buy can be run directly off 12 volts.

The table also shows that fluorescent lights use less power than halogen lights and that LED lights are more efficient again. Very recent advances in technology mean that LED lights are now available in warm colours and only use about 15% of the power taken by an equivalent halogen light. Some are even available as direct replacements for the spotlights found in more recent caravans. Clearly, swapping to this type of lighting is going to make a significant impact on battery life, especially during long dark evenings.

We often get asked about the power consumption of caravan movers with people frightened that using a mover would quickly flatten their battery. Whilst it is true that movers do use a lot of power they are normally used for no more than a minute or two on each outing. The effect of this on a good battery is negligible and nothing to worry about.

Using power efficiently is the first step to managing without a mains hook up. After that it’s time to consider how we can supplement the power provided by the caravan’s battery. The simplest and most cost effective way of getting additional power is to buy a second battery. This can be swapped with the main battery when it runs down or alternatively (for telly addicts) be used just to power the TV.

Should you wish to do so it is possible to connect two batteries together. However there should be a suitable fuse local to each battery and (ideally) the batteries should be identical. This arrangement can work well when used in conjunction with solar panels or wind generators (see below). Installation should be by a competent electrician.

An advantage of having a second battery (for caravanners) is that you can strap it in the car boot and charge it from the tow car as you drive around. There are various ways this can be done. The simplest is to make up a lead that plugs into the car’s cigar lighter socket. Such a lead must be fused (max 10 amps) and may need to be unplugged when the engine is not running to avoid flattening the car battery.

As an alternative to using the cigar lighter socket you could have an auto electrician install a split charge relay and connect the spare battery to the car via that. This ensures that the battery is only connected when the engine is producing enough power. It is also possible to purchase at DC to DC battery charger tha will work from the car's 12 volt system and give better charging performanve than a direct connection.

solar panel

 

This 50 watt solar panel is hooked up to two large batteries and easily powers the caravan all
through the summer
 

Another way of providing additional power is by using one or more solar panels. Modern panels give useful output in cloudy conditions and can even be used in the winter months. To be effective though you need a panel with a rating of at least 40 watts. A good quality crystalline panel  will cost about £250 and measure around 500x625mm (20”x25”). Make sure that any panel you buy comes with a charge controller. This will prevent it from overcharging the leisure battery.

With care a 40 watt panel can be enough to keep an outfit running indefinitely during the summer months. In spring and autumn such a panel can greatly reduce the net drain on the battery thereby making it last much longer before becoming flat.

Of course you can go the whole hog and have 2 or even 3 large panels installed on the roof of your outfit. These can then be permanently wired via a suitable controller to the on board 12 volt system – a true fit and forget solution. Beware that this is a job best left to professionals and tha the panels will eat into your persobal effects payload.

Portable wind generators are another excellent way of harvesting some green energy. However those producing useful power can be a bit on the heavy side and need strong guyed poles to support them. This could be why they are no too popular. Also some form of speed control is essential to keep noise down and maintain safety. Combining wind generation with solar power is a good way of maintaining self sufficiency for extended periods outside the summer months.

Conclusion
There is no need to be afraid of using a caravan or motorhome without a mains hook-up. As long as you are careful about the power used, a good battery should last at least 3 days without charging. A second battery will double this and, if coupled to some means of charging, may well provide indefinite lasting power. So – get out to those big open spaces, have fun!

smilie