To fuse or not to fuse (split from memorial day install)

Post by **ttocs** » Tue Jun 08, 2010 6:59 am

looks good but only one concern, where is the fuse for the rear battery? Is it under the floor wher the wire goes down?

Power wires MUST be fused with in 12"-18" of the battery, doesn't matter which one.

AAMP217 · Post by **AAMP217** » Wed Jun 09, 2010 11:19 am

ttocs wrote:looks good but only one concern, where is the fuse for the rear battery? Is it under the floor wher the wire goes down?

Power wires MUST be fused with in 12"-18" of the battery, doesn't matter which one.

I disagree I would have to pull the IASCA rule book to double check. The fuse at the front of the car is protect the wire from a dead short. Another fuse near the rear battery does not protect the wire more. In reality his rear fuse is only protecting about 3 feet of 1/0 gauge. All that fuse in the rear is doing is stealing voltage.

GX3 · Post by **GX3** » Thu Jun 10, 2010 9:02 pm

jbob0124 · Post by **jbob0124** » Fri Jun 11, 2010 4:42 am

AAMP217 wrote:
ttocs wrote:looks good but only one concern, where is the fuse for the rear battery? Is it under the floor wher the wire goes down?

Power wires MUST be fused with in 12"-18" of the battery, doesn't matter which one.
I disagree I would have to pull the IASCA rule book to double check. The fuse at the front of the car is protect the wire from a dead short. Another fuse near the rear battery does not protect the wire more. In reality his rear fuse is only protecting about 3 feet of 1/0 gauge. All that fuse in the rear is doing is stealing voltage.

I was always under the impression that you needed a fuse after every battery (within 12-18")

Post by **ttocs** » Fri Jun 11, 2010 5:16 am

I am glad to know I am not the only one he disagrees with.

I thought rule #1, right after you do not talk about fight club was that you fuse 12"-18" batteryPERIOD.......

AAMP217 · Post by **AAMP217** » Fri Jun 11, 2010 5:20 am

jbob0124 wrote:
AAMP217 wrote:
ttocs wrote:looks good but only one concern, where is the fuse for the rear battery? Is it under the floor wher the wire goes down?

Power wires MUST be fused with in 12"-18" of the battery, doesn't matter which one.
I disagree I would have to pull the IASCA rule book to double check. The fuse at the front of the car is protect the wire from a dead short. Another fuse near the rear battery does not protect the wire more. In reality his rear fuse is only protecting about 3 feet of 1/0 gauge. All that fuse in the rear is doing is stealing voltage.

I was always under the impression that you needed a fuse after every battery (within 12-18")

It is something that at lot of people get confused. Even professionals. The secondary battery is doing no more than recieving and storing a charge from the alternator. If you were in danger of harming the battery the fuse under the hood would still blow before the battery developed a dead short to stop the short. Fuses in the rear of the vehicle are to protec the electronics we put in the car. Most amps have internal fuses for this purpose but it is always better to blow the fuse in the block than in the amp, it is less stress on the amplifier. So in reality the only fuse that is needed in an entire install is the fuse protecting the wire from a short that would cause a fire, any other fuses are just for added protection agaist electronics damage.

jbob0124 · Post by **jbob0124** » Fri Jun 11, 2010 6:22 am

So then having amps that have no internal fuse would require a fuse before the amp, such as a fused distro. block in order to protect the amp correct?

Post by **Rold Gold** » Fri Jun 11, 2010 7:22 am

jbob0124 wrote:So then having amps that have no internal fuse would require a fuse before the amp, such as a fused distro. block in order to protect the amp correct?

Sounds right to me............

shawn k · Post by **shawn k** » Fri Jun 11, 2010 8:05 am

jbob & ttocs are correct: for safety, each battery or battery bank should be fused within a short distance. The fuse under the hood will blow if there's a short and it will stop current from flowing from the front battery, but that does not stop the current from flowing from the rear battery/s to the short. If the secondary battery/s are not fused, a short could certainly burn up the charge cable and possibly cause a fire

eulogious · Post by **eulogious** » Fri Jun 11, 2010 8:15 am

That's what I had to do with my new ti400.2. I had to fuse it seperately. I just went and got a smaller fuse for my fused distro. Problem solved! I believe almost all ti's don't have fuses internally… new ones could be different though. So I should say all older ti's...

AAMP217 · Post by **AAMP217** » Fri Jun 11, 2010 8:28 am

shawn k wrote:jbob & ttocs are correct: for safety, each battery or battery bank should be fused within a short distance. The fuse under the hood will blow if there's a short and it will stop current from flowing from the front battery, but that does not stop the current from flowing from the rear battery/s to the short. If the secondary battery/s are not fused, a short could certainly burn up the charge cable and possibly cause a fire

You do realize he is fusing a lead that is 3 feet long. If that theory was correct then it would need to be fused EVERY 18 inches. The long runs of wire are the ones that have the highest current flow and heat therfore they can short and cause fire. Fuses are in the system to protect the wire. So a dead short before the 18" fuse in the rear would have the same shorting properties. I will have to pull my master MECP book to get the exact verbage for it. I agree that safety is a a concern but a fuse on a 3 foot seciton 1/0 gauge from a secondary battery would not fail unless it recieved somewhere in the vicinity of 500 - 750 amps of current. The battery would develop a short before then.

shawn k · Post by **shawn k** » Fri Jun 11, 2010 8:51 am

AAMP217 wrote:
shawn k wrote:jbob & ttocs are correct: for safety, each battery or battery bank should be fused within a short distance. The fuse under the hood will blow if there's a short and it will stop current from flowing from the front battery, but that does not stop the current from flowing from the rear battery/s to the short. If the secondary battery/s are not fused, a short could certainly burn up the charge cable and possibly cause a fire

You do realize he is fusing a lead that is 3 feet long. If that theory was correct then it would need to be fused EVERY 18 inches. The long runs of wire are the ones that have the highest current flow and heat therfore they can short and cause fire. Fuses are in the system to protect the wire. So a dead short before the 18" fuse in the rear would have the same shorting properties. I will have to pull my master MECP book to get the exact verbage for it. I agree that safety is a a concern but a fuse on a 3 foot seciton 1/0 gauge from a secondary battery would not fail unless it recieved somewhere in the vicinity of 500 - 750 amps of current. The battery would develop a short before then.

The objective here is not that you are protecting the <18" from the battery to the fuse, but in fact it's the other side of the fuse that's being prtected (the long run from front to back/back to front).

Look at it this way: Let's say that you have the typical fuse at the battery under the hood, but you do not have a fuse at the battery in the rear. If you were to have a short somewhere in between the front fuse and the rear battery (like the firewall for instance), you would have a dead short at the rear battery. The fuse under the hood would probably blow (eliminating any current flow from the front battery), but there's nothing protecting the charge cable from the rear battery and "high" current would flow from the rear battery to the short via the carge cable.. make sense?

Post by **ttocs** » Fri Jun 11, 2010 8:54 am

jbob0124 wrote:So then having amps that have no internal fuse would require a fuse before the amp, such as a fused distro. block in order to protect the amp correct?

no matter how many batteries.

Post by **ttocs** » Fri Jun 11, 2010 8:59 am

I am not sure how you think that the 2nd battery would not be as big of a fire hazzard as the 1rs, it has the same possibility to do damage as the 1rst regardless of its location. In fact with the 2nd one being inside the car, woundn't it be the real fire hazard? what happens if he throws a screw threw some trim 4 ft from the 2nd battery, or pinches it and shorts it out? Your saying the one fuse up front will protect both batts? I do not see how that works, welcome the verbage from the master manuals that say it and would still work question it and install a fuse no matter what. The fuses location on the car is not as important as it location on the wire, fuse it ever 18 inches, really?!?!?!?!?

AAMP217 · Post by **AAMP217** » Fri Jun 11, 2010 9:03 am

ttocs wrote:I am not sure how you think that the 2nd battery would not be as big of a fire hazzard as the 1rs, it has the same possibility to do damage as the 1rst regardless of its location. In fact with the 2nd one being inside the car, woundn't it be the real fire hazard? what happens if he throws a screw threw some trim 4 ft from the 2nd battery, or pinches it and shorts it out? Your saying the one fuse up front will protect both batts? I do not see how that works, welcome the verbage from the master manuals that say it and would still work question it and install a fuse no matter what. The fuses location on the car is not as important as it location on the wire, fuse it ever 18 inches, really?!?!?!?!?

Please re-read my posts, fuses protect the wire not the battery.

Post by **Rold Gold** » Fri Jun 11, 2010 9:09 am

How about just using a TMC902 and be done with this BS................

Shawn makes a great point with the reverse flow from batt 2 back to the front.......

But the use of 2 902's would solve that problem.

I guess it really comes down to the installer and his methods of running cable...... Personally, I try to route it through places I'd never drop screws into or even disturb once in. Gromets and e-tape are my best friends at any and all possible problmatic spots. Not to say that it never happens even to the most skilled installers but I like to beleve most of us here overthink our installs and take these things into account....

shawn k · Post by **shawn k** » Fri Jun 11, 2010 9:19 am

Any fuse/fuse holder would work fine as long as the fuse itself is not rated higher than what the cable is for a specific length.

So the 902's would work fine

jbob0124 · Post by **jbob0124** » Fri Jun 11, 2010 10:30 am

But if you used the 902's on the battery up front, wouldn't you still need to fuse just before your amps (provided they don't have fuses themselves) to protect them? The fuse at the battery is going to be rated higher then the amps recommendation. Which if you had a short at the batteries fuse, wouldn't that end up hurting the un-fused equipment in the back?

shawn k · Post by **shawn k** » Fri Jun 11, 2010 11:36 am

Yeah....the equipment would need individual fuses. When we were talking about the 902's it w
as referring to protecting the cable

jbob0124 · Post by **jbob0124** » Fri Jun 11, 2010 12:16 pm

Gotcha

gbody805 · Post by **gbody805** » Fri Jun 25, 2010 12:31 pm

I would have to say go with two fuses to be safe. On for each battery.

Look at it this way.

If you take the front battery wire and fuse it with-in 18" to protect the wire running towards the amp. But in this case towards the rear battery, which just happens to be in line before the amps.

Then why wouldn't you fuse the rear battery 18' from the rear battery on the same wire just before the battery.
If you look at it in reverse.
Lets say your factory battery in located in the rear and your amps are in front.
Wouldn't you fuse it like normal.

Like it was said before.
Just for instance. The wire shorts to the fire wall. Bad grommet or no grommet altogether.

The front battery fuse will more then likely open.

Problem solved

Well now the section that is on the others side running under the carpet to the rear has no fuse.
With an optima or one of the other high current batteries normally used, there should be enough current to heat even a 0/1 ga. wire to the point of melting the casing.
With a fuse in the rear the current draw should open the second fuse.

It might not be in the rule book but I would rather spend an extra $40 to save my thousands invested if the whole car goes up.

shawn k · Post by **shawn k** » Fri Jun 25, 2010 1:54 pm

gbody805 wrote: It might not be in the rule book but I would rather spend an extra $40 to save my thousands invested if the whole car goes up.

If it's not in the "rule book" IASCA, USACi, MECP or otherwise, the book should be thrown in the garbage. Espeacially MECP... Horrible company!!

It's basic fundamental 12v wiring

dedlyjedly · Post by **dedlyjedly** » Sat Jun 26, 2010 1:12 am

AAMP217 wrote:
It is something that at lot of people get confused. Even professionals. The secondary battery is doing no more than recieving and storing a charge from the alternator.

You have stated in this thread that the in-line fusing protects the wire and I agree with you on that. So are you arguing that the second battery doesn't store enough "charge" to melt or burn up a power wire when a dead short occurs in the 12 volt circuit?

AAMP217 wrote:Fuses in the rear of the vehicle are to protec the electronics we put in the car.

Protect them from what exactly? I contest that fuses at or near the amp are also utilized to protect the wire. They protect the wire in the event of amp power supply failure that would in turn present a dead short on the 12 volt circuit. An amp's on-board fuse is really only going to protect the amp itself in the event that someone hooks up the power and ground backwards...but that doesn't really offer any added protection for the amp during normal operation.

AAMP217 wrote:Most amps have internal fuses for this purpose but it is always better to blow the fuse in the block than in the amp, it is less stress on the amplifier. [/color]

Please explain how blowing an in-line fuse is less stressful on the amp than blowing an on-board fuse of equal value.

dedlyjedly · Post by **dedlyjedly** » Sat Jun 26, 2010 1:52 am

AAMP217 wrote: The long runs of wire are the ones that have the highest current flow and heat therfore they can short and cause fire.

That is incorrect. Do you understand that a long power wire and a short ground wire hooked up to an amp are both REQUIRED to pass the exact same amount of current for the amp to operate properly? I think what you're trying to communicate here is that the longer your power wire has to be the more it effectively reduces the amount of current it can pass safely. That tidbit isn't really relevant to this discussion though.

AAMP217 wrote: I agree that safety is a a concern but a fuse on a 3 foot seciton 1/0 gauge from a secondary battery would not fail unless it recieved somewhere in the vicinity of 500 - 750 amps of current.

Again, that is incorrect and not really applicable. A fuse will typically fail when passing somewhere in the range of 150-200% of its rated value for a determined period of time. The percentage range and period of time will vary from fuse to fuse. I believe you meant to say that "...WIRE on a 3 foot section 1/0 gauge...would not fail unless it received somewhere in the vicinity of 500-750 amps of current."

I don't mean to be a dick by picking through your posts, but as you said, it can get confusing and we want to clear up what we can.

dedlyjedly · Post by **dedlyjedly** » Sat Jun 26, 2010 2:01 am

shawn k wrote:
If it's not in the "rule book" IASCA, USACi, MECP or otherwise, the book should be thrown in the garbage. Espeacially MECP... Horrible company!!

It's basic fundamental 12v wiring

It seems that I agree with your opinions on basic fundamental 12v wiring, but certainly not with your assessment of MECP! What do you have against that organization?