quick note dont forget to factor in lower voltages as this will push the amps up a bit
55w/14v=3.92A running/charging
55w/12v=4.58A stoped/ok
55w/11.5v=4.78A flat!
so dont forget to uprate the cable above the duty needed!
or the smoke will leak out of your cables
when i was at collage studing auotmtive engineering/design/eletronics
the rule of thumb was to work all of this and factor it into everything
and i thort it was a compleate waste of time
the idea is fine for working out fuse sizes but i would be factoring in 15-20%
above duty for cable sizes
stuf like bulbs,fuel pumps etc may well be uprated in the future