inline fuse Main power wire

[quadzilla]

I was wondering if it would be a bad idea to use 1 of the slots of a 4 position fused (ANL) distribution block,for the main power wire for the battery (0gauge).Instead of the normal inline fuse setup. Battery is located in the trunk.

[Notladstyle]

not really needed if the battery is in close proximity to the amps. The only thing a fuse would do it add resistance.

[quadzilla]

not really needed if the battery is in close proximity to the amps. The only thing a fuse would do it add resistance.

sounds good,perhaps i should have explained more,the wire i was refering to is the main power wire for the battery running from the front of the car to the battery.

[Notladstyle]

Lead acid batteries produce electricity by means of a chemical reaction. That chemical reaction also produces heat. The larger the electrical draw, the more heat.

The reason why there are fuses at the front of the car near the battery is to protect the battery in case of an accident or other mishap puncturing the power cable and forcing it to contact ground through the chassis. If the cable were to ground out the surge in current would produce so much heat the battery would explode showering the engine bay in corrosive acid.

Theres no reason to fuse the wire in the back of the car because the point of the fuse is to protect the run of wire from the front to the back.


If you are talking about putting the 4 slot ANL fuse at the front of the vehicle, this would be good as long as the fuse holder is rated for the extreme heat in the engine bay.

[TJElite]

Lead acid batteries produce electricity by means of a chemical reaction. That chemical reaction also produces heat. The larger the electrical draw, the more heat.

The reason why there are fuses at the front of the car near the battery is to protect the battery in case of an accident or other mishap puncturing the power cable and forcing it to contact ground through the chassis. If the cable were to ground out the surge in current would produce so much heat the battery would explode showering the engine bay in corrosive acid.

Theres no reason to fuse the wire in the back of the car because the point of the fuse is to protect the run of wire from the front to the back.


If you are talking about putting the 4 slot ANL fuse at the front of the vehicle, this would be good as long as the fuse holder is rated for the extreme heat in the engine bay.

Where does this myth keep coming from?

The fuse in the main power wire is also to prevent fire in the cabin. If the main wire shorts to ground, either in an accident, or if its gets pinched under a seat bolt, etc., the current between the battery and the short will cause the wire to get really hot, and possibly start a fire. Batteries exploding from the short circuit is the least of your worries.

If you put a battery in the back, you have the same problem going forward. This is why the old IASCA rule book called for any wire passing between compartments to be fused within 18 inches of the battery.

The wire between your battery in the trunk, and the one under the hood passes through multiple compartments, and therefore must be fused at each battery bank.

Think about it. You have two batteries, connected by a wire. It is fused up front. Now, it shorts in the middle. Front fuse blows, rear battery continues to feed power into the short, until something bad happens.

As for the resistance issue...it is negligable, at best.

Toby

[P057]

can we test this with a spare semidead optima redtop that I have?

You do have a pretty big back field near the Buddha statue Mr. Johnson?:D

[Notladstyle]

Where does this myth keep coming from?

The fuse in the main power wire is also to prevent fire in the cabin. If the main wire shorts to ground, either in an accident, or if its gets pinched under a seat bolt, etc., the current between the battery and the short will cause the wire to get really hot, and possibly start a fire. Batteries exploding from the short circuit is the least of your worries.

If you put a battery in the back, you have the same problem going forward. This is why the old IASCA rule book called for any wire passing between compartments to be fused within 18 inches of the battery.

The wire between your battery in the trunk, and the one under the hood passes through multiple compartments, and therefore must be fused at each battery bank.

Think about it. You have two batteries, connected by a wire. It is fused up front. Now, it shorts in the middle. Front fuse blows, rear battery continues to feed power into the short, until something bad happens.

As for the resistance issue...it is negligable, at best.

Toby

I already tested it. A lead acid battery grounded by a 4ga wire will explode. Its not a myth.

[TJElite]

The myth is that the wire doesn't have to be fused, not that the battery will or will not explode.

Actually, most battery explosions are not just heat, but heat and hydrogen gas, and most are caused by overcharging, vs. short circuit. Optimas and other AGM batteries don't release nearly the hydrogen (they were actually developed around a mil spec for this) and typically won't explode. I have seen them short circuited (and actually shorted on myself, once). I have never seen one explode, and they gave up LOTS of current in the mean time.

I have seen 3 vehicles over the years have major interior fires due to the wire between the two batteries not being fused.

The test would be to run a 4 ga between two batteries, and then drive a screw through the wire, into the floor of the car. I bet it will burn, and burn badly, before the battery explodes.

Or, for arguments sake, lets say that the battery would explode first, and a fuse would prevent that. Wouldn't you rather spend a couple $$ on a fuse, vs. having battery acid and bits thrown all about the inside of your car?

I think we all agree that the wire has to be fused at the front battery. Any argument as to why that battery should be fused can be applied to the rear battery...what's the difference?

So far, the only down side presented here to putting in a second fuse is resistance, to which I call BS (yes, it will add resistance, no, it won't make any measureable difference). The only other downside might be cost, but I think its much cheaper than any failure mode.

Toby

Toby

[Notladstyle]

If the battery is in the trunk near the amps, what good is an inline fuse?

[TJElite]

If the battery is in the trunk near the amps, what good is an inline fuse?

The same 'good' as the fuse is up front. Why do you put that one in?

Why is so hard to comprehend that if you have to protect a wire from the current of a battery, or a battery from exploding, at one end, you should do the same if there is a battery at the other?


One more time. You have two sources of potential (batteries) at either end of the wire. If a short occurs between the two, bad things happen. If you fuse the wire at the front, the front battery comes out of the circuit, but not the back one. It continues to either push current through the wire until something burns, or it explodes. Either is bad.



Toby

[TBSpyder]

I've yet to see a battery explode, however I have seen several fires inside the vehicle due to the wire heating up and subsequently melting the jacket off it.

[Notladstyle]

by explode, do you mean fire and flames? I mean battery acid sprays all over. I wouldn't fuse a battery that is less than a foot from the amps it powers. I don't see anything suffering from an extra fuse though... unless its a cheapo that actually does present a voltage drop.

[pnrcaraudio]

Toby is absolutely correct, car's catch on fire because of silly cheap mistakes, spend a few extra dollars to do it correctly and you will not end up spending large amounts of mon ey to fix something else.

[quadzilla]

damn easy guys, i didnt want this to turn into a car exploding thread hehe,also the fuses that were on the battery originally were for the radiator fan,ignition,mpi none were for keeping the battery from exploding.I used a odyssey 925 for the relocate anyhow.Back to the question would it be ok to replace the 250a inline fuse that is 18" away from the battery now,with a 4 position distribution block with the same fuse etc.

[joebobclark]

Toby and Dalton, I think you guys are thinking different here.

If Im reading correctly, Toby is saying 2 fuses in the same wire between the front and rear batteries, less than 18in from each battery, to prevent the rear from feeding the short. Dalton is saying 2nd fuse after the rear battery, between the battery and amp, is not needed. Correct me if Im wrong.

As for the original question, using a 4way fused block instead of a single inline fuse is fine, in any case....

[TJElite]

correct. I am talking about the wire running between the front and rear battery. It needs to be fused on each end.

Now, as for not needing to fuse between the rear battery an the amps, I would agree, as long as the amps are fused. If the amps are not fused, then you need fuses in those lines, as well, even if they are short.

Suppose, for example, an output in the amp goes south (like from too low impedance, or whatever). This usually results in a dead short between power and ground. If there is no fuse, current continues to flow until the circuit is interrupted (wire burns away) or the current source is removed (battery blows up). Neither is good.

In short, fuses are relatively cheap, and as long as they are installed properly, are worth it.

Back to the original post, using 1 fuse on a 4 gang block is fine, as long as you it will accomidate the proper size fuse and wire. I like to use this arrangement for the rear fusing, so I only have to use one block. I'll use a 1/0 in to 4 4/8 ga out. The input goes to the positive of the rear battery. One of the 4 ga outputs is for the 4 ga going to the front battery, and they I can use the the other 4/8's for amps or whatever.

Running a multi fuse block up front isn't a bad idea, either. Then, you can have things like fused alternator to battery conncection, and easy distribution for anythinge else you might need up there, in addition to fusing the main system power wire.

Toby

[MCOR]

Got to agree on the fuses near each battery. Do you know how a MIG/TIG welder works? That is what you turn your vehicle into if the positive cable shorts to the body. Causes NASTY problems at minimum, serious injury or death at extreme.

Having worked many years for Ford, I unfortunately dealt with many stories of peoples cars catching fire in their garage and buring the house down (some cases people even were seriously injured or killed). From faulty ignition switches to cruise deactivation switches, and Contour wiring harnesses, they were all fused somewhere but still not enough to keep from a fire starting in a short ckt situation.

I always err on the over-safe side of the fence these days-FUSE IT ALL!!!

[Notladstyle]

I can see fusing the rear to protect against equipment shorts. I doubt in an accident it would do much good at stopping a short (if its bad enough to unsheathe 1ft of wire it will short the battery at the terminals) but its more likely a person would fry an amp than total their car, wait, this is tamparacing, I take that back...

[TJElite]

I can see fusing the rear to protect against equipment shorts. I doubt in an accident it would do much good at stopping a short (if its bad enough to unsheathe 1ft of wire it will short the battery at the terminals) but its more likely a person would fry an amp than total their car, wait, this is tamparacing, I take that back...

I still think you are missing the original point. I'm talking about fusing the 18+ foot of wire going from the rear battery, to the front battery, at both sources of potential (batteries). For one, I could easily see this wire getting pinched in an accident, and for another, if you bother to fuse it at one end, why not the other?

Imagine the car gets tboned. The 4 ga wire running near the door sill, between the two batteries, gets cut, and shorts to the frame. Now, you have two batteries (one front, one rear) feeding current into this short. The front fuse clears, so that battery is out of the loop, but the rear battery keeps feeding the wire, which gets hot, and starts a fire.

This is a no brainer, and I am having trouble understanding why someone who finds 'no challenge in car audio any longer' doesn't get it.

Does anyone else understand what I'm saying? Can anyone translate this into Dalton-ese for me? :-)

Toby

[MCOR]

I can see fusing the rear to protect against equipment shorts. I doubt in an accident it would do much good at stopping a short (if its bad enough to unsheathe 1ft of wire it will short the battery at the terminals) but its more likely a person would fry an amp than total their car, wait, this is tamparacing, I take that back...


Dalton, you keep referring to a small 1 foot run of cable. Are you talking about just adding a battery in the trunk and running a positive cable straight from it to the amp that is also in the trunk? If so, you still have to tie it to the front battery/alternator to keep it charged. Where would you suggest tying it in? All second battery installs we have ever done/seen are as Toby seems to be explaining-running a 15-18 foot positive cable from the rear of the car (new trunk mounted second battery) to the front battery to tie the electrical system together. We have always (don't do it much anymore) and have always seen it with a max fuse within a few inches of the rear battery terminal-again to cover that 15-18 foot run in case the cable gets shorted in an accident, lift pinch, other incident.

Draw one of your pictures-maybe I too am misunderstanding this tandem battery system with no fuse at the terminal.

[Notladstyle]

I see the need for a fuse both ends of the supply wire but I wouldnt fuse between the rear battery and the amp. Just doesnt seem optimal to me. that extra .000004 ohms is worth it :p