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Unread 08-22-2013, 10:13 AM   #1
Prot
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What size fuse for 200 amp alternator

I am upgrading the charging system on my 2007 JK. I am going with dual batteries and a 200 amp alternator from Mean Green. While I am at, I am doing the big 3 upgrade.

I have been researching the various aspects of this as I slowly gather all the parts. My JK is my only vehicle and I live quietly alone, hence all the planning.

I am going to replace the positive wire that goes from the alternator to the battery. It currently has a fusible link. I am replacing this wire due to the higher output alternator and of course, will need to have an inline fuse.

I was only able to find one source so far on another forum where this fuse is specifically mentioned and the guy used a 300 amp fuse.

Does that sound right? I don't want to use a fuse that is too big and something go wrong, causing everything to melt as well as cause other damage. On the other hand, if the fuse is too small, it will blow constantly.

I was also hoping for somebody to point me in the right direction for a high quality fuse. I am hoping to get this done right the first time and put an end to my electrical woes.

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Unread 08-22-2013, 11:39 AM   #2
Holder350
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I am not an advocate of a so called "high output" alternator.

The amperage the alternator can output is directly related to the size of the windings, rectifier, and the amperage rating of the rectifier diodes.

Most late model alternators are so tightly packaged into their cases (unlike the GM CS alts) that there is physically no more room in the case to upgrade the components.

So unless you find an alternator manufacturer that is building an alternator in an aftermarket case you are being fooled by them posting peak amps and not rated continuous amps.

Let's for a minute say that your alternator is capable of outputting 200amps continuous, and that the load on your system is the same (200amp) that would mean the required gauge wire would be somewhere in the 1awg or 0awg range to successfully sustain that amp draw.

My advice is to do the dual battery setup with a good isolator and keep your current OEM alternator and wiring in place. The added reserve capacity will do you much more good than a "high output" alternator will ever net you.
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Unread 08-22-2013, 12:00 PM   #3
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Mean green is a reputable company and has been building high output alternators for jeeps and other vehicles for years. The idea that Jeep or any other automobile manufacturer is building them at the highest capacity or quality is ludicrous. The stock alternator on a JK puts out 160 amps. The replacement puts out 200 amps. It is not outside the realm of reason that a 40 amp increase is possible with this type of alternator.

I am not here to debate the merits of the alternator I have purchased. I thought I would seek some helpful advice on fuse selection. I just sent an email to mean green asking them for advice.
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Unread 08-23-2013, 01:53 PM   #4
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I agree with holder350 on using 0awg. As far as the fuse I recommend using an ANL style fuse. And the size should reflect whatever the max output is on the alternator. It will most likely never reach it's peak. And in the rare occurrence it does you will be protected. I would not recommend using any type of circuit breaker or any thermal switching circuit that you can reset. These usually have greater tolerances and are not as safe and reliable.
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