# Fuse at the battery?



## lunchmoney (Dec 27, 2007)

Total newb question:

Do I need a fuse in the power cable near the battery?

I'm running a single 5-channel amp (infinity 5350a) with a 4 gauge power cable. It's the only thing running off this cable.

If so, why? Isn't that what the amp's fuses are for?

Thanks


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## Hillbilly SQ (Jan 26, 2007)

you should ALWAYS fuse 18" or less from the battery. this is to protect the wire from accidentaly shorting out and causing a fire. i'd fuse that piece of 4awg at 80amps for safety sake. go to www.bcae1.com and look at their wire tutorial/calculator. it's #16 in the scrolldown list to the right.


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## lunchmoney (Dec 27, 2007)

ok, thanks!


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## annoyingrob (Aug 24, 2007)

yes, fuses on power wires aren't there to protect the amps, they're there to protect the wire


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## lunchmoney (Dec 27, 2007)

I have an inline fuse from my wiring kit, the fuse says "AG60A" on it... I assume that means it's a 60 amp fuse... would this be ok to use?


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## doitor (Aug 16, 2007)

As TEAM SHIMANO/FALCON sayd. You should ALWAYS fuse near the battery. If you don't you can have serious problems.
Plus it's really easy to do.


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

annoyingrob said:


> yes, fuses on power wires aren't there to protect the amps, they're there to protect the wire


Well, kinda, the fuse is to protect the CAR from the WIRE, should the wire get pinched. Most any battery can produce 2-300 amps of current and can turn a power wire into a light bulb filament in a few seconds... burning the car down in some cases...


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## doitor (Aug 16, 2007)

Aaron'z 2.5RS/WRX said:


> ... burning the car down in some cases...


And that's not a very good thing.


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## Hillbilly SQ (Jan 26, 2007)

lunchmoney said:


> I have an inline fuse from my wiring kit, the fuse says "AG60A" on it... I assume that means it's a 60 amp fuse... would this be ok to use?


yes that fuse should be just fine. i doubt that amp will ever come close to popping it. also, make sure you use a grommet when you run the wire through the firewall.


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## Oliver (Jun 25, 2007)

lunchmoney, Welcome to DIYMA !!

here is some of number 16 @ BCAE...




Fuses: 
I've been in the electronics repair business since about 1986 and have come to believe that most people don't understand the function of a fuse, or they just like to let the smoke out of electronic devices (transistors, resistors...). 

Note: 
Letting the smoke out of an electronic device is a process which converts a useful piece of electronic equipment into a paper weight. 

Function: 
A fuse is generally inserted into an electrical circuit for 1 of 2 reasons, either to protect the power source which includes the wire that connects the power supply to the electrical device, or to protect the electronic equipment. The electronic equipment manufacturers specify a fuse rated to open the electrical circuit before damage can be done to the device or open the circuit if the electronic device fails in some way (electronic devices may pull excessive current when they fail). If a fuse larger than the specified fuse is used, a small mistake when installing the equipment may cause catastrophic failure of the equipment. WHEN, not if, WHEN you're thinking of replacing a blown fuse with a higher rated fuse ask yourself if you know more than the engineer who designed the equipment. Don't get in a hurry when installing electronic equipment. Take the time to go get the right fuse. 50 cents for a fuse is better than $50 labor plus the cost of the replacement parts for a repair job. 
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Example: 
In the diagram below, you see that there is a fuse between the battery and the amplifier. In this configuration, the fuse can be used to protect the wire and the amplifier. If the fuse is the proper one for the amplifier, all you have to do is make sure that the wire segments 'A' and 'B' are rated to pass more current than the fuse and you'll be OK. Wire segment 'A' must be as short as possible because it is NOT protected by the fuse. 


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In the next diagram, things get a little more complicated. As you can see, wire 'A' is used to deliver power to the distribution block. Wire 'A' is of a large enough gauge to power both amplifiers. 4 gauge wire is commonly used as a main power wire. Fuse 'A' must be rated to protect wire 'A'. Any fuse rated at less than ~150 amps is sufficient to protect a 4g wire and the vehicle (if the 4g wire is longer than ~15 feet long, you may want to limit the fuse to ~125 amps). Again, fuse 'B' protects wire 'B' and fuse 'C' protects wire 'C'. Wire segments 'X' and 'Y' MUST be as short as possible because, unless they are of the same gauge as wire 'A' (or larger), they could be a fire hazard. 


In most cases, the wire size is reduced at the point of distribution. ANY time that the wire size is reduced, you must add a fuse in the line (at the point of distribution) to protect the smaller wire. Look at the following for more detailed info about changing wire sizes. 

What you should know about the image below (Please excuse any redundancy. This is important.): 
Wire "A" is unprotected which is why you want the main (125 amp) fuse as close to the battery as possible. If this length of wire gets shorted, it WILL burn. 
Wire "B" is protected by the 125 amp fuse. It has to be at least 4g. Anything smaller wire would possibly burn before the fuse would blow in the case of a short circuit to ground. This wire feeds all of the power to the distribution block. 
Wire "C" is supplied power from the dblock. Since it's also a 4g wire, it needs no fuse. The main wafer fuse will protect it and the vehicle in case it's shorted to ground. 
Wire "D" is a smaller wire. It's also supplied power by the dblock. Since this wire is smaller (let's say an 8g wire), the main fuse can not protect against a short circuit. If the 8g wire shorts to ground, it will burn (and possibly take the vehicle with it). This would be a very unsafe condition. 

The fuse you will be using can be increased to the larger amount shown here if your amp causes the 60 ampere fuse to blow.

If your amplifier has fuses , these will protect the amp in case there is an excessive current flow to it.

Awesome first post


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## lunchmoney (Dec 27, 2007)

Thanks guys...

I just installed a Rockford Fosgate fuse holder with an 80 amp fuse, about 6 inches from the battery. Piece of cake. Sounds like 20 bucks well spent. It turns out that the 60 amp fuse I had wouldn't fit the 4 gauge wire.

What I'm embarrassed to admit is that the system is already installed, and I've been driving around for a couple of months without the fuse...  

Glad that's taken care of.

This is the first complete system I've ever done by myself... my last car I had done by a shop, and they didn't install a fuse.... they also used what looked to be 10 or 12 gauge wire, and mounted my amp to a piece of chipboard with wood screws... so go figure.

Great vibe on this forum. Very unintimidating for a newb like myself. 

Thanks!!!


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## doitor (Aug 16, 2007)

Pictures. Pictures.
 
We love pictures.


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## Hillbilly SQ (Jan 26, 2007)

lunchmoney said:


> Thanks guys...
> 
> I just installed a Rockford Fosgate fuse holder with an 80 amp fuse, about 6 inches from the battery. Piece of cake. Sounds like 20 bucks well spent. It turns out that the 60 amp fuse I had wouldn't fit the 4 gauge wire.
> 
> ...


umm...i don't know whether to laugh or vomit about the hack job that "shop" did. were they an established shop or a pawn/tint/rim shop that also does car audio on the side?

glad you're already comfy on this humble little forum. we definately promote self-teaching because when you read and do yourself you'll retain the info a lot better than if you're "spoon fed". we'll definately elaborate on your questions though after you've done your research. the amount of knowledge in this place is second to none. welcome to the addiction.


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## lunchmoney (Dec 27, 2007)

TEAM SHIMANO/FALCON said:


> umm...i don't know whether to laugh or vomit about the hack job that "shop" did. were they an established shop or a pawn/tint/rim shop that also does car audio on the side?
> 
> glad you're already comfy on this humble little forum. we definately promote self-teaching because when you read and do yourself you'll retain the info a lot better than if you're "spoon fed". we'll definately elaborate on your questions though after you've done your research. the amount of knowledge in this place is second to none. welcome to the addiction.


The chipboard was covered in felt, so I wasn't even aware of how crappy the install was until it started coming apart... oh, and did I mention that the first time it rained after the install my firewall was leaking.... yeah. super job they did.

Yes, they're a combination 20" chrome rims / 25+ hp intake kits / coffee can exhausts / car audio shop... this was about 8 years ago, certainly haven't been back since.


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## bobditts (Jul 19, 2006)

sounds like a similar install I saw in a ford lighting truck. whoever did the install used a fuse holder at the battery but didnt bother using a fuse. Insted it was just a chunk of solid metal. Not only that, but the fuse holder was mounted to a chunk of MDF (highly flammable) wrapped in carpet right next to the engine. 

I agree, you should definitely post some pics of your current gear. If you have a before shot of your engine bay without the fuse, take an after shot and post them both up. Its always nice to see the difference this site has on people.


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## lunchmoney (Dec 27, 2007)

bobditts said:


> sounds like a similar install I saw in a ford lighting truck. whoever did the install used a fuse holder at the battery but didnt bother using a fuse. Insted it was just a chunk of solid metal. Not only that, but the fuse holder was mounted to a chunk of MDF (highly flammable) wrapped in carpet right next to the engine.
> 
> I agree, you should definitely post some pics of your current gear. If you have a before shot of your engine bay without the fuse, take an after shot and post them both up. Its always nice to see the difference this site has on people.


Oh ****... my amp is mounted to a piece of mdf... the same stuff one might make speakers out of... is this a no no?


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## Hillbilly SQ (Jan 26, 2007)

lunchmoney said:


> Oh ****... my amp is mounted to a piece of mdf... the same stuff one might make speakers out of... is this a no no?


that's acceptable.


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## bobditts (Jul 19, 2006)

lunchmoney said:


> Oh ****... my amp is mounted to a piece of mdf... the same stuff one might make speakers out of... is this a no no?


 
Thats perfectly fine. Although ive never heard of anyone making a speaker out of mdf Baffles, yes, but not the speaker lol. What I said earlier was that the MDF was in the engine bay right next to the engine. It gets very hot near there and the mdf has the potential to combust. Amps dont get very hot (or atleast they shouldnt) nor do they spring leaks or throw sparks so mounting to mdf is fine.


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