Here is a very simple formula that everyone can use to figure out how many amps a particular light, electronic item, etc draws. Take the rated wattage (such as 55 watts for a light) and divide that by the voltage its run at. For a FJ at idle it will be battery voltage (around 12.5 volts) and when running it would likely be around 13.5 to 14 volts.
A standard 55 watt bulb at 13.5 volts will draw 4 amps at 13.5 volts and 4.4 amps at 12.5 volts. A pair of 55 watt lights will draw around 8 amps continuous
You can also figure out the wattage of a electrical item if you know the voltage and the amperage. Take a 9,500 pull rated superwinch, that can draw 450 amps at 12.5 volts. Take the 450 amps, multiply that by 12.5 volts, and presto a impressive 5,625 watts.
With LED lighting it can get interesting because the lights themselves don't draw much power. Sometimes they claim say "55 watts of light output" but that has more to do with comparing it with a standard 55 watt bulb then it does actual current drain. Its important to really look at the numbers. Also ballast fired HID lights often times have starting amp draws much higher then running current draw. This is important because you can have wiring/charging system that can handle the lights when running, but during firing they draw enough power to melt wires and or beat up on the alternator.
A standard 55 watt bulb at 13.5 volts will draw 4 amps at 13.5 volts and 4.4 amps at 12.5 volts. A pair of 55 watt lights will draw around 8 amps continuous
You can also figure out the wattage of a electrical item if you know the voltage and the amperage. Take a 9,500 pull rated superwinch, that can draw 450 amps at 12.5 volts. Take the 450 amps, multiply that by 12.5 volts, and presto a impressive 5,625 watts.
With LED lighting it can get interesting because the lights themselves don't draw much power. Sometimes they claim say "55 watts of light output" but that has more to do with comparing it with a standard 55 watt bulb then it does actual current drain. Its important to really look at the numbers. Also ballast fired HID lights often times have starting amp draws much higher then running current draw. This is important because you can have wiring/charging system that can handle the lights when running, but during firing they draw enough power to melt wires and or beat up on the alternator.
