Best 100 amp fuse option? (1 Viewer)

[Skniper]

Figured I'd post this question here as it is basically the electrical Forum. From a recent discussion in the 60 Forum, I'm looking to run a direct wire from my FJ62 alternator to the battery to upgrade the 25 year old wiring harness.

Based on the 80 amp fj62 alternator, my plan is to run a 4 or 6 ga wire with an inline 100 amp fuse. Question is: what's the best "style" of 100 amp fuse to run?....ANL, AMG, Maxi?? Does it matter?

Don't know one option from the other. Thanks.

 

[John McVicker]

I did this on my 60 and used a 65 amp Maxi Fuse...your 62 alt puts out more juice however, & I'm not certain Maxi Fuse has one larger than 80 amps.

If you can find a 100 amp Maxi Fuse, I'd think that would be fine.

John

 

[Bogo]

You may wish to figure out the right size fusible link. They tend to be more tolerant of short term overloads like when charging up a dead battery. Also, just being a short piece of moderately undersized wire they can be a lot cheaper, and the spare is much more durable than any fuse. Another thing is you never want the alternator to become disconnected from the battery when it is outputting current. When that happens, many alternators die permanently.

The fusible link between the alternator and battery is there to protect the battery from discharging through a shorted alternator wire, like during an accident. It would take a set of near miracle circumstances for an alternator to damage a battery via over current. Over voltage situations, which is how alternators kill batteries, won't be stopped by a properly sized fuse.

Most fusible links are a 5 to 6 inches long at the battery end of the wire. If it blows, typically you can use a crimper and crimp the two ends together and get home, assuming the issue that caused the short is fixed. If the issue isn't fixed, it will just get hot, melt and blow again. When you hook it up again, you can feel the fusible link wire, and if it is getting hot you can disconnect. They are really very slow blow fuses. If a fusible link blows in a few seconds it was to small. It should take 10 to 20 seconds to heat up and blow.

Sizing. When I looked out for sizing a fusible link I found a few sites that said 4 AWG smaller than the wire size being protected, and 5 to 6 inches long. That way the voltage drop is minimal, and the fusible link will go first in catastrophic situations like dead shorts.

Sadly for us hobbiests, a spool of the right sized non flammable insulation wire made for fusible link use may cost as much or more than a fuse plus holder and then one will have 99' extra wire left over.

Quickly looking around I found this place, MadElectrical Fusible Links, and others. They are selling fusible link kits that are 4 AWG smaller than the wire size they are to protect. At under $4 each plus shipping they are very reasonable too. Looks like you could substitute any size eye on the battery end. They recommend crimping, soldering, then covering with heat shrink tubing. Normally I'd say stay away from soldering, but in this case it will move the heat up and fuse spot to the middle portion of the link. Some places on Amazon Market Place sell fusible link wire in a number of different AWG sizes in 25 foot spools.

 

[John McVicker]

Bogo, that MadElectrical site has some really good info. I've bookmarked it for future use and purchase.

Thanks, John

 

[Skniper]

Wow, thanks...interesting info @Bogo , will spend some time on that website too. Really throws a wrinkle in the use of a classic fuse for this application.

My intention is to leave the factory harness connected to the alternator while adding the supplemental direct wire from alt to battery. The protection built into the old factory wiring will still be in place, which I assume runs through the factory fusible links already at the battery. Obviously the new direct wire would need a safe fail point too.

So with an 80 amp FJ62 alternator I was thinking of using about a 6ga wire...which would give me a 10ga fusible link wire.(?) Is that overkill? Anything smaller than 10 just seems, well, small. Any additional thoughts on this??

 

[george_tlc]

32V MIDI Bolt-Down Fuses - Bolt-Down Fuses - Littelfuse

Midi fuses have a delay time built in, they are ideal for protecting wiring. I've used them on my old patrol when the fusible links died of old age etc. But on the patrol, I had rewired a lot of things, so midi fuses made sense. With existing wiring, fusible links work pretty well if they are essentially factory spec and have the connectors etc.

cheers,
george.

 

[LandCruiserPhil]

 

[JCruse]

I'm with Phil, I haven't yet changed out the apparent 4 or 6 awg from my Alt yet but everywhere else in my 2 battery rig I used Bussman resettable breakers. Except for one post mounted Blue Sea MRBF that goes on the 1awg to the back of the truck. That might be a good option. You can mount it right on the alternator!


Available fuses go from 30 to 300 amps

Amazon.com: Blue Sea Systems 5191 Fuse Block Terminal 30-300 AMP: Sports & Outdoors







.

 

[TrickyT]

32V MIDI Bolt-Down Fuses - Bolt-Down Fuses - Littelfuse

Midi fuses have a delay time built in, they are ideal for protecting wiring. I've used them on my old patrol when the fusible links died of old age etc. But on the patrol, I had rewired a lot of things, so midi fuses made sense. With existing wiring, fusible links work pretty well if they are essentially factory spec and have the connectors etc.

cheers,
george.

Choices, choices, choices. Didn't know about MIDI fuses, but just to throw out another option Littelfuse also makes MEGA fuses: UL Recognized Mega® Fuse Series - High Current Fuses Automotive Passenger Car from Fuses - Littelfuse. They have a slightly larger form factor than the MIDI and are marketed specifically for automotive and marine applications. They use the same time-delay technology and come in 100-500A sizes. I used them in my dual battery setup. A nice aspect of both MIDI and MEGA is that the fuse holder terminals are studs and not spring clips like those found on blade-type fuses.

 

[Corbet]

I'm with Phil, circuit breaker for 100a. I use a 60a on my fuse block inside the truck that runs all the extra accessories like Fridge, HAM, etc....