Technical 175 amp fuses???

firstinsteele · Jul 25, 2023

Wow! Just WOW!

Ben

Crazy Steve · Jul 25, 2023

73chevelleLS4 said: ↑

We wanted to clear the air here. There has been quite a discussion on this subject without folks understanding the engineering that went into the decision to use the Mega Fuses in many of our kits. I am a site member here, and also work at AAW as one of the design engineers. The 175 amp Mega Fuse (not Maxi Fuse) is used in many OE GM, BMW, Audi, VW, etc. applications to protect the main circuit to the energy center (Fuse panel). We chose these because when a fusible link blows, it can create quite a mess, and in some instances, even cause a small fire. The fuse serves 2 purposes: 1. To protect the main feed in the case of a catastrophic failure (EG: a front end collision that shorts the main feed to ground). In this instance, that fuse will blow in .5 seconds. 2. To protect the main feed in the case of a slow overload (a gradual draw over what the system's capabilities are). They are rated at 175 amps because they are intended to be mounted out under the hood just as in an OE application where the industry standard under hood temperature is understood to be 200-250 degrees F. With that temperature in mind, that fuse degrades to about 110 Amps. This information was well researched with the engineers at Little Fuse who manufacture these fuses. A 10 gauge GXL/SXL wire is capable of handling about 103.5 amps before degradation begins. 103 amps would be an extremely high draw in most any vehicle, and would only happen on very rare occasions or builds.

Placing the Mega Fuse holders inside the car or in the trunk, are not suggested for 2 reasons. By mounting the fuses in the passenger compartment (cabin or trunk), in the case of any type of failure, you are now bringing a hi-tension, unfused 12V battery lead into the vehicle and allowing the unprotected circuit to enter the cabin instead of leaving it outside of the vehicle. Extremely bad idea. Also, by mounting them in the cabin, where the air temperature is ambient, the fuse is now rated too highly to properly protect the system. That is why we suggest, just as the OE applications are done, to mount them out under the hood close to the battery, starter and alternator. This allows for the circuitry to be fused properly, and in the case of a catastrophic failure, keeps any instance of a fire outside of the cabin or trunk.

As far as placing the alternator on a fuse, that was done as a safety issue in case the alternator shorts to ground, and yes, although rare, that can happen. Probably overkill, but not a bad thing.

With all this in mind, we chose these fuses because they are very clean, and when they blow, there is no mess and no cutting of wires to re-splice as with fusible links. Simply fix what caused your problem, open the mounting case, and replace the fuse.

All of this was done with keeping the safety of our customers and the integrity of our product in mind. We certainly could have continued to use fusible links, but the safety and clean installation that these fuses just makes for a much better product.
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I've got a question. How many individual strands in the #10 wire you use in your harnesses?

Mike_B · Aug 15, 2023

Mike_B said: ↑

Decided to use #8 wire for the charging circuit. It will be routed from the battery to a distribution block.
Click to expand...

I actually ended up using a 60 amp mega fuse instead of fusible link to protect the 8 ga wire. It's mounted on the inside fender lip next to the battery.

After reading AAW's post, it sounds like I should use a 100 amp fuse instead, due to the derating at under-hood temperatures. Correct? I still haven't done anything to protect the 10 ga panel feed wire

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Technical 175 amp fuses???

firstinsteele
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from Wichita Falls, TEXAS

Crazy Steve
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from Beautiful outer Yelm WA

Mike_B
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from North Texas

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Technical 175 amp fuses???

firstinsteele Member from Wichita Falls, TEXAS

Crazy Steve Member from Beautiful outer Yelm WA

Mike_B Member from North Texas

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firstinsteele
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from Wichita Falls, TEXAS

Crazy Steve
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from Beautiful outer Yelm WA

Mike_B
Member

from North Texas