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Fuse Size??

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=10978
Printed Date: August 02, 2025 at 6:16 PM


Topic: Fuse Size??

Posted By: 2k2Accord
Subject: Fuse Size??
Date Posted: March 16, 2003 at 1:18 PM

I know there is a way to find out what size fuse you would need, so I'm not going to ask if there is, I'm just going to ask what it is,  I have to Amps, one for my highs/mids, and one for my subs, respectably a 50 squared, and a 250 squared, I'm running it with 4 guage wire from the battery to the distribution/fuse box, and was wondering what size fuse would I put on the 4 guage wire, riht after the battery??  Also, I need 4 fuses in the block, cuz each amp is dual power/dual ground, what would you suggest puttin in there, fuse wise that is??  Thanks a lot guys

Accord



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A person's real worth is determined by what the do, when they have nothing to do......



Replies:

Posted By: dragonrage
Date Posted: March 16, 2003 at 1:23 PM

Easy way: add together the fuse ratings for each amp and that's what you need for the wire that runs them all

Hard way (only use if needed): Max current draw = (Amp_Wattage / Battery_Voltage)/Amp_Efficiency

Amp wattage is total, battery voltage will be between 12 and 15 volts, Amp Efficiency is a decimal < 1.

Go a bit higher than the output of that.



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2009 Pontiac G8 in planning stage
HU: ?
Speakers: ?
Amps: ?




Posted By: bberman1
Date Posted: March 16, 2003 at 1:33 PM
What ever you do don’t count the fuses that’s the wrong way. What you want to do is add up the RMS wattage and then divide by the volts. For example if you have 1000 watts rms you would then divide that by say 13.8 (what ever voltage your car has when running) so 1000/13.8 = 72.46 or about 73 amps




Posted By: dragonrage
Date Posted: March 16, 2003 at 1:46 PM
bberman: you have to account for amplifier efficiency!!! A class AB amp will draw about 3x the power that equation gives you! And yes, you can add up the fuses, because current splits in a parallel circuit and the amps are in parallel. Why do you think some amps have 2-3 blade fuses in parallel?

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2009 Pontiac G8 in planning stage
HU: ?
Speakers: ?
Amps: ?




Posted By: pilot_chris
Date Posted: March 16, 2003 at 10:40 PM
Dragonrage is right, you just simply add the max amp draw (which is usually posted in the front / back of the amp manuals) and put in an appropriate fuse. Going bigger will completely negate the fuse since it allows too much power to flow through and then you're putting your hopes on the amp fuses which is not what you want to count on stopping a surge (too close to sensitive componets).

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95 Cavalier 2.2L
High Output Alternator
Rockford 1 Farad Punch Capacitor
JL 500/1 for RF Punch HX2 500 watt RMS subs
MTX 4244 4 channel for Polk & Pioneer door and rear deck speakers





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