wiring amp to its own battery

[528hz 10+ year member]

You would use a 300a fuse at each location. Three 100a fuses inline would only give you the ability to pass 100a at each fuse.

Are you sure about that? Wouldn't that limit the current passing? You can fuse too much. Three 300a fuses would be WAY too much.

 

[dman4486 5,000+ posts]

Are you sure about that? Wouldn't that limit the current passing? You can fuse too much. Three 300a fuses would be WAY too much.

what are you questioning? 3* 300a fuses would be too much what?

 

[528hz 10+ year member]

what are you questioning? 3* 300a fuses would be too much what?

Yeah, 3-300a fuses would be way too much.

Why not just run 1-300a fuse? I understand because of the distance that one might want to add 3 fuses, but you don't need three 300amps.

 

[dman4486 5,000+ posts]

Yeah, 3-300a fuses would be way too much.
Why not just run 1-300a fuse? I understand because of the distance that one might want to add 3 fuses, but you don't need three 300amps.

because you want to have a fuse between any power source and a long run to prevent unintentional grounding. and the 300a rating is for the wire itself. 300a break point between any power source and a potential ground such that you don't have bombs in the vehicle.

 

[dman4486 5,000+ posts]

and just for my input, I would only run the 2 fuses between the batteries assuming:

#1. the amp has fuses onboard

and

#2. the run from rear batt to amp has no potential of grounding ie. it is short and running only in the trunk.

 

[528hz 10+ year member]

because you want to have a fuse between any power source and a long run to prevent unintentional grounding. and the 300a rating is for the wire itself. 300a break point between any power source and a potential ground such that you don't have bombs in the vehicle.

I see your point about fusing between power sources, therefore he really only needs 2 fuses. One under the hood and one in the back before the amp.

All my batteries are in the back and I'm not use to thinking about a front battery anymore. I just run 1-300a fuse on mine, and that is because of the lack of distance between all my bats.

 

[Subst4nce 10+ year member]

I don't mean to thread Jack, but in that picture, is that the ground from the amp wired to the negative of the 2nd battery, which is then grounded and wired to the first battery?

 

[loopkiller 10+ year member]

and just for my input, I would only run the 2 fuses between the batteries assuming:
#1. the amp has fuses onboard

and

#2. the run from rear batt to amp has no potential of grounding ie. it is short and running only in the trunk.

I would agree to the two 300a fuses if the amp wire was shorter than the nearest grounded metal. So if the closest grounded metal was 20 inches from the POS+ post on the rear battery and the amp was 18 inches away, the fuse is not necessary.

That said, in a daily vehicle, the additional fuses will not affect the amount of voltage you see at the amp or affect output. The only downside is the cost, which is about $10 per fuse.

 

[loopkiller 10+ year member]

I don't mean to thread Jack, but in that picture, is that the ground from the amp wired to the negative of the 2nd battery, which is then grounded and wired to the first battery?

Yes. The more grounds the merrier.

 

[dman4486 5,000+ posts]

I see your point about fusing between power sources, therefore he really only needs 2 fuses. One under the hood and one in the back before the amp.
All my batteries are in the back and I'm not use to thinking about a front battery anymore. I just run 1-300a fuse on mine, and that is because of the lack of distance between all my bats.

the fuse in the back would have to be before the rear battery. the long run is between the two batteries and there is a source at both ends.

 

[Subst4nce 10+ year member]

Yes. The more grounds the merrier.

K, thank you //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[badstang123 10+ year member]

the fuse in the back would have to be before the rear battery. the long run is between the two batteries and there is a source at both ends.

x2 if you want to do it right.

Can you get away with not doing it? Probably...will it ever be a problem? Probably not. Is it perfectly safe without a fuse near the rear battery....NO!

Think of it this way for those that think you don't need one of the fuses. The wire in the diagram loses it sheath and starts arcing to ground right in the middle of the car to the chassis. The fuse near the front battery will blow and the front battery will be of no concern. The rear battery however will have a fireworks show giving everything it's got since there is no fuse to blow near the rear battery and therefore nothing to stop current. Two sources of power...two fuses.

As far as to the amp. In my last car I fused to the amp as well even though it was a short run. I could see skipping it but I would still prefer the safety net.

 

[loopkiller 10+ year member]

Here is the best dumbed down way i could think of explaining this.

When you have a power source like a battery, it has the ability to store electrons that are used to do work. Some work examples would be lights, sound, or heat. Basically, when electrons flow, they will do some work.

Now, since electrons flow in a circle in a DC system, the are created on the positive plates of your battery and flow out of the POS+ post of your battery. They then follow the shortest path back to the NEG- post. They don't care what they have to do to get there, they just want to get there.

So if that shortest path is a dead short, they will do some work in the form of heating up the wires making the connection. That heat will typically start a fire given we are talking about fairly large batteries. Even some of the smaller audio batteries like the HC600 has enough stored power to produce near a thousand amps at a dead short. That will melt even the best 1/0 wire for sure.

So what you have to ask yourself is this: Are you SURE that your POS+ wire will NEVER short out? Imagine a rear end accident. Your battery has the chance of moving around and not being exactly where you intend it to be under normal circumstances. In that circumstance where you are rear ended and the battery is shorted, if you have a fuse, it will blow opening the circuit. No fire. Now if you didn't fuse that wire, then you can be sure to have a fire on hand and you better be able to get out of that car before it melts through the trunk floor and hits the gas tank.

Are you sure you don't want that $10 fuse?

 

[stilltippin863 10+ year member]

do you have to run a ground from front battery to back battery??? if not how would you wire the batts

pos+ from front to back battery and then neg off back battery to frame?? will this method keep the back battery charged?

 

[nimrod 10+ year member]

do you have to run a ground from front battery to back battery??? if not how would you wire the batts
pos+ from front to back battery and then neg off back battery to frame?? will this method keep the back battery charged?

Yes, run a wire from the front neg. to the rear neg. Just follow the diagram that loopkiller posted. It is very clear and very simple to follow.