Fuse size to use

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jrcr_15

jrcr_15

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Hello,
I have upgraded my alternator to 80 amps and have run new wires into the interior and done the amp bypass, along with installing a volt meter.

The new wires are 8 gauge to carry the heavier load from the alt etc. I am opting to go with a fuse vs the fusible link just to make it a bit more plug and play.

The wires going into the fuse will be 12, but not sure what fuse to use in this holder. As referenced here: Improved Wiring for older Mopars

Suggestions? Please and thank you!
 
Are you talking about the main charging lead from alternator to battery? You want something larger than 12. Look up what circuit protection should be for #8 wire 8 might not be ALL that large for an 80A alternator

If you are running a "one wire" alternator the charging wire needs to be MUCH larger than "normal" because the voltage sense is AT the alternator, and whatever voltage drop is in the charge wire will allow the system voltage "at the other end" to sag

According to this website, no6 wire should be fused for 80A

Wire Sizes and Fuses
 
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67Dart273 said:
Are you talking about the main charging lead from alternator to battery? You want something larger than 12. Look up what circuit protection should be for #8 wire 8 might not be ALL that large for an 80A alternator

If you are running a "one wire" alternator the charging wire needs to be MUCH larger than "normal" because the voltage sense is AT the alternator, and whatever voltage drop is in the charge wire will allow the system voltage "at the other end" to sag

According to this website, no6 wire should be fused for 80A

Wire Sizes and Fuses
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As always you are very helpful.. thank you
 
I would use no more than a 30 Amp. But the easiest thing to do is measure the current flow on the wire and add a fuse that is about 25% greater than the current flow. You may find that you do not need a very large fuse this way

Plus I would disregard the 80 amp output when considering the fuse size. Its like I have 400 amp service on my house but the largest fuse I am using is a 60 amp split phase and that is for a tankless water heater. I could probably get away with a 150 amp service but it is what it is.
Just because the power is available, does not mean you will use ALL OF IT
 
I would use no more than a 30 Amp. But the easiest thing to do is measure the current flow on the wire and add a fuse that is about 25% greater than the current flow.
Click to expand...
Good info, & what kind/type of fuse should a person use?
 
Pawned said:
Depends on the fuse block you purchase. I use the inline fuses on a couple ckts and the flat for the fluse block
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inline fuse holder with common round OE type glass fuses that's easy enough. On the flat ones do you mean the later type, the flat plastic colored ones with the 2 male tangs that plug in?
 
I rewired my Duster and spilt up the circuits. The original fuses were the 6 glass fuses. I rewired the car myself. I built my own wire looms and connectors. I spilt my wiring into 20 fuses ranging from 3 amps up to 20 amp. Plus I replaced the fusible link with a 30 amp fuse located in the engine compartment
 
Rapid Robert said:
what kind of fuse did you use on that "critical" one
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I have an inline fuse holder and just a standard 30 amp spade fuse like you described above

But if you are still doing any wiring buy a lot of the fuses. they blow immediately at a short or overload (which I think is good) They are not that expensive
 
Rapid Robert said:
noted & appreciated. thank you again!
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Getting back to the original question of this thread. I have a 40 or 50 amp alternator. I have 10 awg wire attached to it, which is over kill but I had the wire so I used it.
The "critical" fuse is 30A so obviously, I really should not need any wire larger than 16 awg. As nothing can use over 30A (combined). I would not use any wire larger than #10awg on the alternator or anywhere else in the vehicle for that matter.

As a matter of fact, even the headlights use #18awg wire. Which in my opinion is too small. you will get too much voltage drop in the wire and dimmer lights. I would not use anything less that #16 or even #14 on the headlights.
I added headlight relays next to the battery to cut down on the length of the wire to the headlights and reducing voltage drop.
 
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