Information for motorcaravanners – Managing your electrics A wet and dreary weekend, let’s stay in and watch television/play CDs. It’s cold, let’s use the blown air heating, evening comes and the lights grow dim. We have used up most of our available battery power, oops! With the increased amount of electrical gadgetry we fit and expect in our motor homes it is important we understand the consumption rate of our items. More and more at rallies and on quiet sites we hear the rattle and hum of generators or people returning to their units needing to run their engines when they discover that their leisure or living space battery has insufficient power left to run the required facilities. How many times has this happened to you or someone you know? First let us consider the source of our electrical power in the living accommodation of our motor home. If you spend most of your time on pitches with mains electric ‘hook-up’ then the following article may be of little interest but for those who don’t and regularly find themselves without battery power for their living needs then maybe the article below will help them manage their power more efficiently. Most motorhomes have a secondary battery fitted to provide these services. In earlier years this was often just another vehicle battery either charged from the vehicle engine whilst travelling or independently charged before departure. In modem units the leisure battery is a specialised battery that can be totally discharged and then recharges again without detriment. These are fitted through charging units, which allow for either charging from the mains when on hook-up or trickle charging from the vehicle alternator when on the move. These batteries are measured in ampere/hours and generally are 75-110 aH. Developments in the field of battery construction mean that with the carbon batteries you can get a larger output battery that is lighter in weight. One living space battery should suffice for year-round weekend use, providing you are careful about how much use is made. Ever more facilities in a Motor Caravan rely on 12v. We now rely on: • Electric pumps for water and toilet flush. The average pump uses 3-5amps, whilst it is not used continuously the total usage for drawing water, showering, etc. can soon add up. lf you have even a small leak in the water system the pump can 250 Motor Caravanners’ Handbook 2022
“cycle” using power. • Fan assisted heating, although heating systems run on gas or diesel the ignition and any circulation fan(s) run from the 12v system. Approximate current consumption for this is 1.4amp. • Electronic ignition for gas appliances (not a great user of power, but inconvenient if you can’t light the fire). • Extraction fans for kitchens and toilets, again the current consumption for these is similar to that for the heating fan. • Even a simple thing as the lighting can run away with power as although the average 8 watt tube light uses no more that 2/3amp, prolonged periods of multi use can soon add up. • Filament lights take a little more current so can run away with the power quickly. Care needs to be taken that lights in cupboards and lockers are not accidentally left on. These should ideally be fitted with a micro switch so the door controls the light being on. It is a good idea to replace filament bulbs with LED type. They use far less current and are available as straight replacements, in most cases tubes can also be replaced the same way. • Heavy current users e.g. colour TV, which can use over 3 amps reduce time available. Add to this CD players, video games or use of computers for the younger motor caravanners, satellite systems and the current is soon used up. A note to remember if you are using an invertor to power mains equipment then there is more current consumption by the invertors, especially if it includes a fan, and that the invertor will consume some power if left on even if no current is being drawn. To decide which are your great power users – if current consumption is not quoted on the equipment then a quick calculation using Ohms law where power (watts) divided by voltage gives the current will enable you to see where the heavy users are. If you venture away from the beaten track or do not want to rely on hook-ups then you may want more capacity. It is correct that leisure batteries are designed to have steady drain and then recharge. Starter batteries are made for a quick burst of power to start an engine and then the alternator will recharge the battery. They are not made for long steady drain of power. Traction batteries tend to be rather large and expensive. these are designed
