TECH TIPS................................ Using D.C. electricity
To understand how D.C.(direct current) electricity may require 0.25 Amps whereas a kettle may need works, think of water passing from a tank, through 15 Amps which may be more current than the a tap, along a pipe and onto a waterwheel. The vehicle’s wiring and sockets are designed to carry. water in the tank provides the pressure and this can be compared to “voltage” and is measured, of course, in “volts”. The flow of water is controlled by the tap and this represents the resistance
In such a case several things may happen: a fuse could blow, wiring could overheat and melt or the socket could overheat and damage itself or the kettle’s plug.
which the electricity will experience as it travels along a wire. The amount of water passing along
D.C. electricity has a major drawback: when it
the pipe becomes the current which is measured travels along wires it quickly loses strength. This is in amperes or “Amps”. Finally, the water hits the known as “voltage drop”. The longer, thinner and water-wheel and makes it turn. The rate and hotter the wire, the greater the resistance and the pressure at which the water turns the wheel is the power produced and is measured in “watts”.
fewer the volts that make it to the appliance being
powered. So, although electricity can start off at well over 12V when it leaves the battery, by the time
To calculate the number of Amps required for a it arrives at the appliance, passing through yards of piece of equipment to operate correctly, use this formula:
Amps = Watts / Volts. A 12V TV may use 48 watts of power. When the TV is operated from the
cable and a socket, it may only measure 11V or even less. With lights this isn’t a problem - they’ll just dim - but some appliances, TVs for example, are so sensitive that inadequate voltage may
mains, the Amps being used will be 48 watts / 230 cause problems such as sound but no picture, lack volts = 0.2 Amps. Hardly anything really but, if you of brightness or they may simply not work at all. were powering the same TV from the 12V battery The solution is to ensure that the wiring between in a vehicle, the sum would look like this: 48 watts / 12 volts = 4 Amps.
battery and socket is as short as possible and
heavy enough to allow the electricity to flow as easily and freely as possible.
It’s essential to ensure that the wiring, fuses and sockets between an appliance and the battery to which it’s connected are all “fit for purpose”. This should always be borne in mind whenever an appliance is plugged in and appears not to work.
It’s absolutely essential to ensure that wiring and sockets are up to the job. If they’re not, not only may the appliances being powered not work correctly but damage could be caused and, at
When an appliance is plugged into a 12V/24V worst, a fire could start. socket it will attempt to draw the amount of power which it needs to run correctly. A ‘phone charger
If in doubt, consult an auto-electrical specialist. Remember: Amps = Watts Volts÷
When installing an inverter or a battery charger, it’s essential to use the correct gauge of cable. This is a guide as to what cable you should use between the battery and the charger or inverter.
To calculate the current consumption in Amps, use the following equation: Watts / Volts = Amps. For example: an inverter with a 12V input and a 230V output of 2500 watts will have a current consumption of 2500 / 12 = 208. Therefore, for a cable run of 2 metres, 90 mm cable should be used.
Charger or inverter current consumption
Charger or inverter current rating
0-25 Amps 25-45 Amps 45-85 Amps 85-125 Amps 125-180 Amps 180-330 Amps
Cable run distance 0 – 1.5 mtr
6 mm sq 16 mm sq 25 mm sq 35 mm sq 50 mm sq 70 mm sq
Cable run distance 1.5 – 4 mtr
10 mm sq 25 mm sq 35 mm sq 50 mm sq 70 mm sq 90 mm sq
Please note that if there is a problem obtaining for example 90 mm sq cable, simply use 2 x 50 mm sq, or 3 x 35 mm sq. It does not matter if you use one cable or ten as long as the square area adds up. Performance of any product will be improved by thicker cable so, if in doubt, round up.
Prices and models can change. For up to date prices, to find a dealer near you or for further information on any of our products, please phone us on 01327 312233 or visit our website:
www.roadpro.co.uk 31
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