Battery in trunk, ran cable through frame rail. How can I fuse this?

[V6UnderPressure]

I ran my Cable through the frame rail to the battery now mounted in the trunk. I have it going to a junction box where the old battery was. I want to fuse this positive battery cable just in case it were to get shorted against the frame. Anyone have any suggestions? Do they sell BIG A$$ Fuses for this? If so, how many amp fuse do I need?

Scott

 

[ThikStik]

If it exists it would be at an industrial electronics place. It woul d need a huge amp rating. Remember, the starter motor uses arc welding ampere levels. For sure, mount fat cable on pass side away from fuel lines.

 

[tom h]

The right fuse would need a tricky combination of passing 100s of amps cold cranking current for 10-15 seconds without blowing, and yet responding to shorter duration accidental shorts much more rapidly. The fuse holder would surely be monstrous.

At these amperage levels may be better off using a fusible link.

A fusible link is typically 3-4 wire sizes smaller than the downstream wiring you're trying to protect.

 

[tom h]

Originally posted by ThikStik
For sure, mount fat cable on pass side away from fuel lines.

Except, the return fuel line is on Pass side, so you can't escape having a battery cable near a fuel line.

Don't tie the cable to the gas line, try to keep a few inches separation.

 

[V6UnderPressure]

I found a fusible link at pep boys with a high rating, when I get a second, I'll jump in the garage and get its rating. What is the difference between a fuse and fusible link? I would assume, that once the link blows, I need a new one correct?

Scott

 

[tom h]

Originally posted by Scott4DMny
... What is the difference between a fuse and fusible link? I would assume, that once the link blows, I need a new one correct?

Correct, they are both "1-time" safety elements, but a fuse is easier to replace.

A fusible link, because it's soldered into the circuit or is otherwise integrated with the downstream wiring, won't have problems with corroded or intermittent contacts in a fuse holder.

Also, Links seem less likely to have spurious or "false" blows than a fuse... when a Link blows, it's because you really did have a current overload.

A link is good when you expect to have extremely few overcurrent incidents, but you positively need fail-safe protection should it be needed.

 

[tom h]

info on very high current fusible links:
http://www.littelfuse.com/data/Technical_Articles/CablePro.pdf

 

[blupuick]

Any good stereo shop will carry circuit breakers rated at 100 amps and up. Very easy to install and no extra fuses rolling around in the car, just find the problem if it pops and reset it. I would suggest putting it as close to the battery as possible.

 

[INEEDAGN]

I second the stereo fuse/circuit breaker idea. You can get them in MONSTEROUS amp ratings and most have terminals already set up for 4/2/0 gauge wire. Quick search on crutchfield.com produced a 300 amp version for ~$15. I'm sure there are bigger ones, and you could always hook up two in parallel if you need 600 amp....

http://www.crutchfield.com/S-SlcnAN4RkNk/cgi-bin/ProdView.asp?g=717&I=211ANL300

bob

 

[V6UnderPressure]

Ok, the fusible link I got from pep boys was 175 amp. Is this enough, If not, I will just get a breaker.

Scott

 

[tom h]

Originally posted by Scott4DMny
Ok, the fusible link I got from pep boys was 175 amp. Is this enough, If not, I will just get a breaker.

Hard to say ... in winter weather the starter could draw a couple 100 amps for a few seconds. Very annoying if the link were to open-circuit!

Do you have access to a DC, clamp-on current probe? Not AC that electricians use, but DC. Typically a DC probe connects in to a hand held Voltmeter (eg, Fluke or similar). Then you can measure what the probable current draw actually is.

 

[Rickracer]

300 amps would do most of the time

But I'd go for 400 to 500, just to be sure you won't wind up with aggravation. You want it to pop if you have a short, not any other time.

 

[KendallF]

Your starter shouldn't be fused, regardless. If you're worried about the long run under the car being hot, run a Ford style remote solenoid and put it in the trunk; that way the cable is hot only during cranking. Mad Electronics offers a nice kit to do this.

 

[V6DVette]

I agree with Kendell on this one. I for one wouldn't want a 1/0 hot wire running the lenth of my car. Heres a link to MADs wiring diahttp://www.gnttype.org/techarea/electrical/Sol.jpg

 

[mweber]

I have always used a 500A MEGA Fuse from Littelfuse along with a MEGA Fuse holder.

http://www.littelfuse.com/data/en/Product_Catalogs/OE101.pdf

Page 17 for the fuse and page 31 for the fuseholder.

Much safer than a fusible link.

The 500A will withstand the inrush current while starting the engine.

Let me know if you have any questions.

Mike