A relay is an electrically activated switch that shortens the distance current has to travel from the battery to whatever device is being powered. This ensures that the optimum amount of current is efficiently delivered to lights, horns, or any other accessory.
Consult the formula to determine what size relay you require:
Total Watts ÷ Voltage = Required Amperage
Step up one level from the indicated amperage load.
Eg. 2 x 55 Watts = 110 Watts ÷ 12 Volts = 9.17 Amps
Use a 20 Amp relay