Caravanning without the orange cable.

by Dave Fawthrop

This FAQ is intended to give some pointers on how to caravan without that orange cable. It does not try to say what is best, because that will depend on your individual circumstances, but does try to give the advantages and disadvantages of each alternative.

[Note from Richard: There are links to one or more solar panel suppliers on the Links page.]

Quick links:

Calculating how much power you need.
Batteries
Solar cells
Wind gererators
Petrol generators
Invertors

Power Requirements.

You should find out how much charge you use on an average day in the van. The maths is simple:
110AH = 1320 watt Hours, at 12 V DC watts= 12 * amps, amps = watts/12.
Find how many watts/amps each appliance uses from labels or instructions. Multiply these by the hours each is used daily. Add daily charge used in watt hours or ampere hours used by each of your appliances together to give daily charge used.

You should replace this charge averaged over 2-3 days. There are many alternative ways of replacing this charge, the choice is yours, and will depend on your personal circumstances.

Batteries.

For general information on batteries see: http://www.batteryfaq.org, this is a bit US oriented, but lead acid batteries are much the same worldwide.

A new fully charged 110Ah Leisure Battery will last most people for a weekend, but very few a week. For longer than that you will have to recharge the battery somehow. Remember that as batteries get older and as they have more use/misuse they will hold less charge, and eventually need replacing.

Leisure batteries are not the no maintenance batteries becoming common in cars. Always check your electrolyte, and top up to marks on the body with distilled/de-ionized water regularly.

You should always charge your batterie(s) before you leave, either on the bench, or by leaving the van powered up, you should give either method several days to fully charge. Cheap chargers make gas, so you must top up the electrolyte. Expensive electronic chargers do not fully charge the battery, and make less gas so need topping up less frequently. Remember also that the electrolyte will evaporate even while the battery is unused.

There is very little power in a leisure battery so you should use it as sparingly as practicable. You should use gas for as many things as possible. You should make sure that the your electric appliances will run off 12 Volts. High power electrical equipment is bad news. A 1000 watt heater used on its own, will run for less than 1 1/2 hours, 500 watts less than 3 hours. 250 watts some 5 hours

The output voltage of a battery falls slowly as a charge is used, and eventually the 12 V equipment will stop working. TVs etc. need as many volts as possible. Thin long wires which may be supplied by the manufacturer or as a DIY addition, may have a high voltage drop. If possible add extra wiring for TV of thick wires ?2 sq mm? or preferably more, and as short runs as practicable. Domestic multi-meters now cost as little as £2.50 and are useful for caravan work.

You can use two batteries. An extra battery can be charged in the back of the car via a split charge relay. If you go out in the car and "do" things while using the van, this should give you enough charge. If you stay on site or just drive to the local town/beach this method will not work for you. The tiny amounts of hydrogen and oxygen produced, should cause no problems, in a well ventilated car, however marine batteries will dump the gasses overboard via a plastic tube. Swap the batteries daily or at slightest sign of low voltage. Be warned however that batteries are heavy and cumbersome to change, and this is not a method for the unfit.

You should ensure that when the van is being towed the battery is actually being charged. There are no less than three ways in which the van can be wired, and three ways in which the car can be wired giving ?5? combinations. To date I have not found a URL explaining this. If you tour continuously this will be important, but if you just tow to a site and eventually home again you can probably ignore this.

Solar Cells

Solar cells are available specifically for vans, but are rated pointing directly at full sun, which rarely happens in UK, but they do give some output even on cloudy days, unfortunately the retailers do not tell you how much.

As a genera l rule you will need *big* cells 25 watts or preferably more.

If you calculate charge needed, as above, you can get a better estimate of the size of cells required.

If possible point your cells due south, slightly below the maximum local elevation of the sun.

Wind Generators.

Wind generators are rated at a high wind speed which rarely happens in an English summer, they give a lower output at lower wind speeds. Many caravan sites in the countryside are surrounded by trees, which reduce wind speeds. Other sites by the seaside are better for wind generators.

As a general rule you will need a 25Watt generator or preferably more powerful.

If you calculate charge needed, as above you can get a better estimate of the size of generator required.

Petrol Generators.

Portable petrol driven generators with 230Vac output can be plugged into your van. They however make a noise which other campers find objectionable. These generators will also charge your battery, but how much will depend on the generator and charger in use.

Most sites will forbid their use during the night, so you will need to use 12V for some of the time.

Invertors.

Invertors which change 12Vdc to 230Vac, are commonly available. Increase the charge calculated above by up to 20% for things run via invertors.

These should be wired directly to the equipment which uses 230VAC.

Do not wire the output of the invertor to the van 230VAC sockets, which run the charger, which runs the invertor, which runs the charger ....