WHAT ABOUT WATTS ?
Annoyingly , not every 12V appliance is rated in amp hours . Power consumption is generally rated in watts . But this is not an issue , thanks to a very simple formula : Watts = Volts x Amps , or Amps = Watts / Volts .
As an example , let ’ s look at a common LED downlight used in the ceiling of most caravan interiors . They are rated at 5W . We know our electrical system operates on 12 volts so , using the formula , a 5W LED light will draw a little less than 0.5Ah per hour .
Running two of the same lights together will consume 1Ah per hour . Three lights will consume 1.5 Ah per hour and so on . The table on this page shows the typical current draw of some common items found in modern caravans .
LED strip lighting is great but , over time , all those LEDs will draw a lot of current .
Device / appliance |
Rating in
amp hours
|
Typical hours of
usage over 24 hours
|
Total amp hours
consumed over 24 hours
|
12V LED television 4.5 4 18 Stereo system 5 3 15 Small LED interior light 0.3 4 1.2
Large LED interior / exterior light
0.5 2 1
LED strip light 1.5 2 3 Water pump 5.2 0.5 2.6 CPAP machine 1.5 8 12
Charger for small USB device
Recharger for large USB device
1 2 2
1.5 2 3
Compressor fridge 6 24 72 ( at 50 % duty cycle )
Gas / diesel heater 3.6 3 10.8
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