Quote:
DC amps to watts calculation formula
The power P in watts (W) is equal to the current I in amps (A), times the voltage V in volts (V):
P(W) = I(A) × V(V)
So watts are equal to amps times volts:
watt = amp × volt
or
W = A × V
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So, to get amps, use watts/volts. To get volts, watts/amps.
For a 55w high beam filament, you need a 55/12 = 4.58 amp fuse. But fuse to protect the lowest-rated cable in the circuit, and a little headroom so they don't blow in normal use.
The stock fuse rating is 8A for each of the low/high beams either side - so 4x 8A fuses.
You need to explain how you've wired your lighting circuit. A 15A fuse is good for something over 200W with the car running (eg 15A * 14V = 210W) - so if you're blowing 15A fuses, it would seem that there's something quite wrong.