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.
LED strip lighting is great but over time,
all those LEDs draw a lot of current.
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.
Rating in
Typical hours of
Total amp hours
Device/appliance
amp hours
usage over 24 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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