Second Battery

[seedubs1 10+ year member]

I'm pretty sure current in the + and - runs are equivelant. So if you fuse the +, then you are in effect fusing the - run since if the fuse in the + run blows, the - run will no longer be carrying current since it is just a big loop. And if somethign happens and the - wire splits (like in a crash), a loose - wire won't cause sparks or anything. So there's no need to fuse it. (Please correct me if any of that is wrong).

And thegreatestpenn, that's not how current works.....

 

[TurdFergueson2 5,000+ posts]

Just want to double check, this look fine? and would 250amp fuse work?

Is the fuse between the amp and battery overkill? I am only using the 2 from the front battery to the one in the back. picture his setup minus the fused run between battery and amp.

 

[seedubs1 10+ year member]

Is the fuse between the amp and battery overkill? I am only using the 2 from the front battery to the one in the back. picture his setup minus the fused run between battery and amp.

Depends how long the wire runs are from bat. to amp, and also if the amp is internally fused. But fuses never hurt anything (unless you are competing), and tehy are always a good safety procaution.

 

[jbizzle 5,000+ posts]

Its not overkill, its just like not having a batt in the back, you need to fuse the wire going to the amp.

 

[jrouter76 10+ year member]

I'm pretty sure current in the + and - runs are equivelant. So if you fuse the +, then you are in effect fusing the - run since if the fuse in the + run blows, the - run will no longer be carrying current since it is just a big loop. And if somethign happens and the - wire splits (like in a crash), a loose - wire won't cause sparks or anything. So there's no need to fuse it. (Please correct me if any of that is wrong).
And thegreatestpenn, that's not how current works.....

you sir are correct, current is equal in that circuit and you also have voltage drops in that circuit which if added up equals the total volts you have from the source before it is sent through the circuit.

 

[jrwalte 10+ year member]

What's different about the ground run that won't cause it to spark if it's carrying the same current as the positive?

 

[jbizzle 5,000+ posts]

If I knew i'd tell you, but I don't //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[dan7532 10+ year member]

What's different about the ground run that won't cause it to spark if it's carrying the same current as the positive?

The chassis is already used as a ground for much of the rest of the car's electrical components. So if the ground run somehow becomes exposed, it will only touch chassis, which is already grounded. Ground wire touching ground chassis = no harm. You fuse the positive wire because positive wire touching chassis = completed electric circuit = BAD BAD BAD. Get it?

 

[jrwalte 10+ year member]

I still can't figure out what is the difference between the positive and negative current if they both carry the same current as mentioned. Obviously the negative, if it carries the same current, is carrying it differently somehow...otherwise it would spark just like the positive.

And what exactly is meant by 'current'? Is that the amperes?

 

[SethPhillips 5,000+ posts]

Why aren't there any fuses on the negative run?

haha you dont need one buddy.. it's a ground wire.. the chasis of the car is... you guessed it, ground..

No, its ground.
And there are fuses on the positive for that reason also.

you need a fuse on ur positve run too!!!

if you are doing a sec batt you need to fuse under the hood. and at back where the wire comes from the under hood batt to the rear batt positive, then fuse from sec batt to amp positive.

Is it even possible for the ground to carry a current that would ever put the wire in danger of melting?

ehh if a positve wire hit that ground wire..

 

[SethPhillips 5,000+ posts]

and this is why the pos wire should have a fuse //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

yes..

but if you knew how current flow's threw a battery you would think diffrent.......

all ways fuse ur + wire's..

just like useing a condom.//content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[seedubs1 10+ year member]

r u serious

I'm pretty sure he was asking because there is current flowing through that wire.....And if there ended up being too much curent passing through the wire, it could melt the jacket and destroy the wire. Especially in a long neg. run like from the trunk to the underhood batt. Not really a stupid question if you ask me.

The answer is because if there is too much current, the + fuses will stop teh flow of current, and because of this, the flow of current in the - run will be stopped. Because of this, as long as you fuse your + run, there is no need to have a fuse to protect your - run, since it is already protected by the + run fuse.

Maybe contribute information to a thread instead of just insinuating that people are stupid and it should be done the way you say because you are einstein

 

[seedubs1 10+ year member]

wow. i get all the respect... i ask if he was serious and now you think i'm einstein

Yup.....Coming up with relativity and all that jazz. They should give you a medal or something.

 

[jrwalte 10+ year member]

The answer is because if there is too much current, the + fuses will stop teh flow of current, and because of this, the flow of current in the - run will be stopped. Because of this, as long as you fuse your + run, there is no need to have a fuse to protect your - run, since it is already protected by the + run fuse.

If the neg is running the same current as the pos why doesn't the neg spark if you touch it against metal (a ground) like the pos does. What about the current changes?

 

[jrwalte 10+ year member]

That still doesn't answer the question. If they both have the same flow of current (as one person said here), what makes the neg different than the pos. This makes me think they don't carry the same current. A google search is getting nothing for me.