# Recommended Fuse Size?



## LAEGER525R (Jan 31, 2010)

I have been researching 4 awg recommended fuse size on bcae1.com. Its 125 amp fuse but the Power Wire Calculator shows my system will have a current flow of 135.9 amps. 

Wire Gauge	
4 awg
Length of Wire	
12 feet
Total Amplifier Power	
1500 watts
Amplifier Efficiency	
80%
Charging System Voltage	
13.8 volts 
Resistance/foot:	
0.00025 ohms
Total Resistance:	
0.002997 ohm
Voltage Drop:	
0.407 volts
Current Flow:	
135.9 amps
Circular Mils:	
41531 

Will a 125 amp fuse pop if the current flow is 135.9 amps? On the site it mentions the 4 awg max size fuse would be 150 amps but they recommend 125 amp fuse to be safe.


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## Kriszilla (Jul 1, 2013)

You're never going to draw max amperage unless you're using sine-waves instead of music. 

You always fuse for the wire. The fuses are to protect the vehicle, not your equipment. A 125A fuse is what you would need for that length of 4 gauge.


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## LAEGER525R (Jan 31, 2010)

Kriszilla said:


> You're never going to draw max amperage unless you're using sine-waves instead of music.
> 
> You always fuse for the wire. The fuses are to protect the vehicle, not your equipment. A 125A fuse is what you would need for that length of 4 gauge.


Thanks for the fast reply. I will get a 125 fuse.


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## 20to20 (Mar 3, 2017)

According to MECP for their AWG and CEA specs for 4 gauge,at 15 ft 4 gauge begins to saturate at 86amps.. having said that, there are many different manufacturers with different versions of 4 gauge.. these are the specs that meet the CEA standards .. of course there are going to be top of the line brands that can hold more current than others.. hopefully this will atleast get u a reference point


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## kyheng (Jan 31, 2007)

For me, getting an 100A fuse also way too much. Unless you changed to higher output alternator and running all your speakers at 1ohm.
I only fuse my Knu's 4AWG OFC with 90A to power an Audison LRX6.9 and JL HD750/1. Never have any problem at all.


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## LAEGER525R (Jan 31, 2010)

Thanks for all the info. I will run a smaller fuse size just to be safe.


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## kyheng (Jan 31, 2007)

Just to add on the smaller fuse size, you need to make sure it won't be smaller rating than the amp's typical current draw.


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## welly.anthony.cat (Aug 6, 2017)

LAEGER525R said:


> I have been researching 4 awg recommended fuse size on bcae1.com. Its 125 amp fuse but the Power Wire Calculator shows my system will have a current flow of 135.9 amps.
> 
> Wire Gauge
> 4 awg
> ...


Your fuse won't simply pop because there may be more amperage running through it than it's rating unless the difference is quite large, the fuse will only pop if overheated via sparking(like if your power cable touches the body or directly to other positive or negative cables) at either end. Other than this it's okay.. 

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## 20to20 (Mar 3, 2017)

welly.anthony.cat said:


> Your fuse won't simply pop because there may be more amperage running through it than it's rating unless the difference is quite large, the fuse will only pop if overheated via sparking(like if your power cable touches the body or directly to other positive or negative cables) at either end. Other than this it's okay..
> 
> Sent from my MHA-L09 using Tapatalk




I'm sorry.. this is purely false ... if a fuse didn't blow at it's labeled rating , it would be pointless to put a rating on it.. fuses don't only blow from direct shorts to ground 


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## welly.anthony.cat (Aug 6, 2017)

20to20 said:


> I'm sorry.. this is purely false ... if a fuse didn't blow at it's labeled rating , it would be pointless to put a rating on it.. fuses don't only blow from direct shorts to ground
> 
> 
> Sent from my iPhone using Tapatalk


Yes I'm very much aware of that I was merely giving an example. Ay FYI you just might be wrong as I'm using a 100amp fuse where a 150amp is recommended for like that past 2 weeks an nothing has gone wrong. But also take into account that internal fuses are more sensitive an seceptable to blowing if a smaller amperage than recommended is being used, external fuses on the other hand which are much larger in size and in amps aren't as sensitive an much more difficult to blow. 

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## DC/Hertz (Nov 27, 2011)

A fuse can flow way more then its rating. It will blow if it's a big spike from a short or if it gets to hot from flowing to much to long. 
Back when MECA was classed by fuse size we could do 30 second drive by runs with a 35amp fuse on a 5000 watt amp. Sometimes it would pop but not every time.


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## 20to20 (Mar 3, 2017)

I'll clamp test a handful today at work and see what the outcome is.. I'll post the results when I'm done with work today 


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## welly.anthony.cat (Aug 6, 2017)

DC/Hertz said:


> A fuse can flow way more then its rating. It will blow if it's a big spike from a short or if it gets to hot from flowing to much to long.
> Back when MECA was classed by fuse size we could do 30 second drive by runs with a 35amp fuse on a 5000 watt amp. Sometimes it would pop but not every time.


Internal or external? If internal how many fuses does it take

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## DC/Hertz (Nov 27, 2011)

welly.anthony.cat said:


> Internal or external? If internal how many fuses does it take
> 
> Sent from my MHA-L09 using Tapatalk


Amps that size don't have internal. 
Btw I could also do burps with a 15amp fuse. 
That was tricky, had to roll into it just right.


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## welly.anthony.cat (Aug 6, 2017)

DC/Hertz said:


> Amps that size don't have internal.
> Btw I could also do burps with a 15amp fuse.
> That was tricky, had to roll into it just right.


U guys some mad risks eh. 

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## DC/Hertz (Nov 27, 2011)

It's not a risk. Fuse pops and that's it. Whatever score you have is the score. 
Now the drive by runs will make you lose if it pops.


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## welly.anthony.cat (Aug 6, 2017)

DC/Hertz said:


> It's not a risk. Fuse pops and that's it. Whatever score you have is the score.
> Now the drive by runs will make you lose if it pops.


That 35 amp fuse, is it the square fuse with two prongs or a tube fuse? 

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## DC/Hertz (Nov 27, 2011)

ANL mostly. But it didn't matter.


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## welly.anthony.cat (Aug 6, 2017)

DC/Hertz said:


> ANL mostly. But it didn't matter.


And the one I'm running for T1500 is an ANL. Lol

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