OK to use two 250 amp fuses as one 500?

[JoeSmith502 10+ year member]

I have a lot of 250 amp fuses laying around but the amp I have requires a 500 amp inline fuse. I was told by the local car audio shopthat I could just double up on the 250's at the same spot and it will act like a 500. Is this a good idea or should I just order a 500 from the internet? Thanks!

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[Andy Somnifac 10+ year member]

No, buy a 500 amp fuse. Wired in series, you would still have one of them blow @ a 250 amp load. Wired in parallel, you theoretically have a 500 amp load capability, but @ a 500 amp load it assumes the resistance on each side of the circuit is equal. A small variance and one of them will blow as the load over it increase beyond 250 amp, then the second fuse will blow as the load from the first fuse is diverted over it.

I would question the knowledge of a shop that is giving advice like that.

EDIT: And dear god, I have a friend who converted a MkI MR2 to run on an electric motor, and it only draws 180 amps under acceleration load.

 

[mokedaddy 5,000+ posts]

You can use two 250s one the same run but they have to be split.

The better question would be what wire are you running that is capable of 500 amps? Unless its a very short run.

 

[JoeSmith502 10+ year member]

The wire is going from my second battery in the back to my amp so the wire will only be about a foot long. The amp also has two positive inputs and two negative outputs so should I fuse both inputs at 500 or what? The amp is a DD Z1A if that helps any. Thanks again!

 

[mokedaddy 5,000+ posts]

Fuse each at 250. Did that with my 40.1 worked fine.

It actually even said that in the manual now that I think about it. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Andy Somnifac 10+ year member]

Ah, two power inputs alters my position. Both fused @ 250 amp should be fine. If it were one input, split between two fuses wired in parallel, I'd stick with my original answer.

 

[PsychoTheRapist 5,000+ posts]

Fuse each at 250. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

x2

 

[JoeSmith502 10+ year member]

Thanks alot for the help everyone!