Fusible link rating

[dmjarosz]

Anyone know the current rating on the fusible link between the alternator and batter? Im upgrading the wiring and want to keep some sort of safety mechanism present. My initial thought is a 300 amp fuse but Im not sure if thats too high or too low.

[jwibbity]

Anyone know the current rating on the fusible link between the alternator and batter? Im upgrading the wiring and want to keep some sort of safety mechanism present. My initial thought is a 300 amp fuse but Im not sure if thats too high or too low.

What alternator do you have? How many amps are you putting out?

[dmjarosz]

I'm running the stock alternator. No idea what its rating is.

[Turbov6Bryan]

300 amp fuse???? Do you plan to weld with your DC alternator?

Omg I have dual DC motors that run on 48 volts and only use a 100 amp fuse because they draw 10 times the load any part on a marauder would ever think about using. 400 aph X 8 batteries

Try a 30 amp fuse

LOL

Something like this is literally lifetime of your car quality

https://www.amazon.com/ANL-Fuse-Audio-Electrical-Protection/dp/B005NJDP6E

[ctrlraven]

Stock alternator puts out 130 amps.

[SteelQualityMan]

The ANL format is a good choice, but 30 amps is far too low an amperage rating. Take a look at HTTPS://www.oznium.com/forum/topic15761 for a discussion on fuse ratings and wire size. They told us the formula for calculating a fuse size in my engineering school days, but I've ate and slept a few times since then and I don't remember. I'll see if I can locate the actual formula for you but I suspect the fuse is going to be more than 100 plus amp rating category.

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[Turbov6Bryan]

The ANL format is a good choice, but 30 amps is far too low an amperage rating. Take a look at HTTPS://www.oznium.com/forum/topic15761 for a discussion on fuse ratings and wire size. They told us the formula for calculating a fuse size in my engineering school days, but I've ate and slept a few times since then and I don't remember. I'll see if I can locate the actual formula for you but I suspect the fuse is going to be more than 100 plus amp rating category.

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Ok. Let's open this up for discussion:)

The factory amp rating on most charging fusible links will be 2 10 amp parallel DIODE links to (pop/blow/go to open) if there is a short to ground

In the case of the charging wire grounding out, you want it to stop before it smolders and catches the car on fire
100 amp is wayyyyyyyyyy too much, no engineering degree needed :)


You have to remember that all the accessories draw amps from the battery, that's why the cable is 0 gauge. The alternator is charging the battery and not a LOAD LINE due to the fact of the DIODES inline. This is why the charging wire being MUCH smaller 8 gauge, because there is no straine on the cable during a heavy load

If you do find that theory on charging wire fuse rating, please post it back up.

Hell I could be way out of line here, 100 amp will let your car catch fire lol

[SteelQualityMan]

I was able to find a technical paper on this topic. I will quote it below:

Quote:What is the normal operating current of the circuit?

In order to select the right amperage of the fuse, you first need to know the full-load

steady-state current of the circuit at an ambient temperature of 25º C (68º F). Once the

current value is determined, then a fuse rating should be selected as to be 135% of this

value (taken to the next standard value).

For example, if the normal steady-state current is calculated to be 10 amps, then a 15A

fuse rating should be selected [10 amps x 135% = 13.5 amps, the next larger standard

size is 15A]. Endquote

Yes, I think it's been established in this forum that the battery runs the car and the alternator charges the battery. Normally, the charging wire would not be a load line, unless it should happen that for some reason the voltage available from the alternator becomes significantly higher than what the battery has available. What you have to look at is not the normal charging current, but the available full load current from the voltage source. In this case, we have a 130 amp alternator. The way I interpret that is that we have a voltage source that can deliver as much as 130 amps to the to the load / battery. Sure, you can put in a 30 amp fuse if you want, but I hope you have a big box of them with you.

I have a 200 amp alternator sitting on a shelf in my garage that I keep meaning to put into my Marauder. The recommended installation kit comes with 6-gauge wire and a 150 amp ANL type fuse. So, for the stock alternator I would probably come pretty close to that hundred amp rating I mentioned earlier.

If you want, I can put up that link to the technical paper when I get back to my home computer. It is quite comprehensive and takes into account a lot of factors that boil down to that 135% fusing recommendation.

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[dmjarosz]

Yes, I think it's been established in this forum that the battery runs the car and the alternator charges the battery. Normally, the charging wire would not be a load line, unless it should happen that for some reason the voltage available from the alternator becomes significantly higher than what the battery has available. What you have to look at is not the normal charging current, but the available full load current from the voltage source. In this case, we have a 130 amp alternator. The way I interpret that is that we have a voltage source that can deliver as much as 130 amps to the to the load / battery. Sure, you can put in a 30 amp fuse if you want, but I hope you have a big box of them with you.

Spot on with what I'm thinking. Suppose you're at wide open throttle, rear defrosters on, blower motor on high, stereo cranking, high beams on, wipers furiously wiping away, and both heated seats on. I bet that draws wayyy more than 30 amps. I know that's an absolute worse case scenario but I'm sure Ford thought of that since they don't want cars with dead batteries all over the place.

The alternator is always supplying the current needed to run whatever electrical accessories happen to be on, plus a little more to keep the battery charged.

A good example of the oppposite of this is when your lights dim at a stop light while your stereo is thumping away. The total draw on the system is greater than what the alternator can output at a given RPM, causing the battery voltage to drop and lights to dim.

150 to a 175 amp fuse sounds about ballpark for a stock alternator. If someone has a spare cable laying around, you could always test with with a welder that displays current live. Though it is a one-time test haha.

[Turbov6Bryan]

I understand that a typical 15 amp automotive fuse can handle upwards of 20 amps for a period of time before it blows, it creates heat then dissolves, usually 20% load capacity before threshold is overcome:)

Maybe I was wrong saying that style 30 amp fuse, it should be a fusible link, not a fuse. The fusible link "length" will distribute heat across the wire before the fuse goes to open....

You would want the charge wire fusible link to pop at a lower amperage as possible, why allow it to create a bunch of heat and start a fire???

Here is a link, he too says 2 parallel fusible links that are 10 gauge 10 amp for our Gmg or Cv.
And here is a pic from my marauder

Good chatting with you, I guess slow blow fusible links vs a standard fuse is a major difference. I'd go with factory IMHO

http://www.idmsvcs.com/2vmod/starter/batterycables/index.html

[Turbov6Bryan]

Spot on with what I'm thinking. Suppose you're at wide open throttle, rear defrosters on, blower motor on high, stereo cranking, high beams on, wipers furiously wiping away, and both heated seats on. I bet that draws wayyy more than 30 amps. I know that's an absolute worse case scenario but I'm sure Ford thought of that since they don't want cars with dead batteries all over the place.

The alternator is always supplying the current needed to run whatever electrical accessories happen to be on, plus a little more to keep the battery charged.

A good example of the oppposite of this is when your lights dim at a stop light while your stereo is thumping away. The total draw on the system is greater than what the alternator can output at a given RPM, causing the battery voltage to drop and lights to dim.

150 to a 175 amp fuse sounds about ballpark for a stock alternator. If someone has a spare cable laying around, you could always test with with a welder that displays current live. Though it is a one-time test haha.

Just trying to keep it from burning up

Factory is 2 10 amp parallel fusible links just letting you decide what rating you should do correctly

Even if you had a 300 amp alternator on it, I'd want the charge wire to go open at the quickest point when grounding out..... That's what the rating on those links is for, quickest short to ground OPEN as possible


LOL not alternator amperage. SMH

[MyBlackBeasts]

The wire awg & color of the fusible link wire indicates the wire's amperage (at least it used to). http://atlanticz.ca/zclub/techtips/fusiblelinks/index.html

[dmjarosz]

Fuses blow pretty darn quick if you short a car battery to ground. Trust me.

What I'm trying to avoid is the fuse blowing during normal heavy usage while still protecting everything in case of a short or alternator malfunction. Can an alternator malfunction even happen?