Top Dog

We all love the idea of pitching our outfit in a big open space but today’s seemingly power-hungry vans and motorhomes cause many of us to stick to established sites with mains hook ups. This is a great shame because, with a little care and investment, it’s perfectly possible to manage without a mains hook up for extended periods. How can this be done? – Read on ….

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’s no mains hook up. Making that battery last is all about using its power as efficiently and economically as possible and, where necessary, using additional sources of 12-volt power, such as a solar panel.

Before going any further it’s worth say that, if you’re going off grid, it’s well worth investing in a good quality leisure battery, one that is designed for off-gridding. You can expect to pay up £150 for a 100-amp hour ‘wet’ battery and more for one that uses AGM (Absorbed Glass Matt) technology.

Leisure batteries have traditionally been of lead acid construction, but these days, lithium batteries are increasingly making an appearance. They can hold nearly twice the power of a lead acid battery for around half the weight. What’s more, they last much longer before needing replacing, hold their voltage much better, and can be discharged more deeply without damage.

Needless to say, there are some downsides. The first is cost – around six to eight times the price of a lead acid type. Secondly, best performance requires a charger going up to 14.6 volts compared to 14.4 volts for a lead acid battery. The good news is that the charger in your Swift group product may be able to be adjusted. Contact the maker (Sargent) for more details.  Lastly lithium batteries can be irreversibly damaged if charged below 0°C. If you can live with these downsides then go for lithium, you won’t regret it.

For outings of 2-3 days with a good, charged lead acid 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 (such as a solar panel) 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 12-volt power consumed
19″ LED colour TV	25-35 watts (2 – 3 amps)
Satellite receiver / Freeview box	12 watts (1 amp)
TV booster	0.6 (0.05 amps)
LED downlighter	3 – 4 watts (about 0.3 amps)
LED strip light	3 – 4 watts (about 0.3 amps)
Fluorescent strip light	6 – 7 watts (about 0.6 amps)
Fan for blown air heating	10 – 25 watts (1 – 2 amps)
Truma combi heating (on gas)	Average 14 watts, 80 watts max, (1.2 – 6.5 amps)
Alde heating	5 watts average (0.5 amps)
Submersible Water pump	25 watts (2 amps)
Diaphragm Water pump	50 – 60 watts (4 – 5 amps)
Caravan mover (singe axle)	360 watts (30 amps)
Caravan mover (quad)	720 watts (60 amps)

Although movers 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.  Anything much more than this could pose a problem.

Using power efficiently is the first step to managing without a hook up. After that it’s time to consider how we can supplement the power provided by the caravan’s battery. Many people choose to install a solar panel, if one has not already been fitted as standard by the vehicle manufacturer. Roof mounting gives a fit and forget solution, but the horizontal mounting means it cannot make best use of the sun’s rays and it will collect dirt, which will impair its efficiency.  If you can put up with the hassle, then a freestanding panel that you keep pointing towards the sun, should give good results from, a smaller and cheaper panel.

Another good way of getting more power is to buy a second battery. This can be swapped with the main battery when it runs down or alternatively (for telly addicts) it could just be used 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. 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 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 auxiliary power socket (cigar lighter socket in older cars). 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. Some motorhomes have the facility to have a second battery as standard, making this a ‘no brainer’ for off-gridders.

As an alternative to using the car’s auxiliary power 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 a DC to DC battery charger that will work from the car’s 12-volt system and give a much better charging performance than a direct connection.

Conclusion
There is no need to be afraid of using a caravan or motorhome without a mains hook-up. Once you’ve learned how you can become independent of a hook up, a whole new world of exciting rallies and beautiful sites will open up – you’ll never look back!

Terry Owen, November 2020