Installed 55w HIDs fuse keeps on blowing

[Minivi]

I just installed some 55w HIDs on my low beams on my 87 325is with US projectors and my fuses keep blowing? Should I put a larger fuse then a 7.5? What should I do?

[gregrego]

55w output, what's the input as marked on the ballast?

[kmarei]

Usually the ballasts have a sticker that says how many amps
I believe my 35w says 6A
So I'd assume the 55w is over 7.5, which blows the fuse
Why not test with 10A fuse?
If it stops blowing, it confirms this is the issue
And it's not a large enough fuse to risk damaging wiring etc

[gregrego]

Agree with above. At 12v, a 35 watt ballast should only pull approx 2.9 amps, so 6 amps for both. Of your ballasts are the old big ones they might pull more I opted for the slim ones they seem to be more efficient. Like kmarei said, the wiring will handle a 10 amp fuse.

[Alex Mc]

P = V*A thus A = P/V
55W /12V = 4.6A
4.6A * 2 = 9.2A
9.2A > 7.5A
So, fuse not big enough.

[gregrego]

that's assuming the ballast is 55w. My ballast says 55w out, 35w in. I'm still running the 7.5 amp fuse.

[bmwguy325is]

Go back to stock BAM! Problem solved.

[Alex Mc]

that's assuming the ballast is 55w. My ballast says 55w out, 35w in. I'm still running the 7.5 amp fuse.

So where is the additional 20W of power coming from?