Specs of fusible link
 

I plan to upgrade some of the wiring in my 05 Freestar. The OEM cable from the battery to the alternator has a fusible link section, so I will use an AGU fuse holder in the upgraded cable.

What amp fuse should I use? i.e. what is the amp rating of the OEM fusible link? 100 ? 200? I prefer to use the 200 amp if that is ok.

Fusible links are designed to sustain a load for a period of time hopefully without the wire catching fire and destroying the components or wiring. They are generally color coded. Where a fuse will open immediately with a load that exceeds the fuse rating , a fusible link will temporarily allow the load to exceed the rating before opening. Fusible links are generally four wire gauge sizes smaller than the wiring of the circuit so as to burn open before the wire in the circuit melts and possibly catches fire. I think you might do a little more research before you attempt to do what you might be planning.

I already know how fusible links work. The only research I have left to do is to find out the amp rating of the fusible link, which I hoped to learn by posting the question here.

Is there some particular reason you are considering rengineering the manufacturer's as built system?

It's called the "Big 3" upgrade, to make the charging/electrical system more efficient. Just google it and you can read about it.

I plan on eventually going to a dual - battery setup to power an inverter, mainly for a small cube frig and chargers and a laptop. Part of mini RV conversion, although I am building it so it is easily converted back.

I've decided that a 200 amp fuse will be fine for my purpose and wiring I will use.

Now I have some idea of where you are. Sorry I cannot offer any further assistance except , I hope your vehicle's engine can handle the additional load you are planning on installing. Many times companies claim to be able to do anything, but we learn too late that it can't always be done. Do you know if the engine can handle the high charging rate for a long period of time with lights, A/C and other power requirements you may be planning to install while possibly trying to climb a hill?

Well, the battery isolator will only charge the 2nd battery after the main battery is charged. And the little cube frig only draws about 40 watts, from the 2nd battery, when the compressor runs, so it can run quite some time without the 2nd battery being charged. That's really the main load, along with just charging a phone and running a laptop. When driving again, the 2nd battery will get charged again, but the charging "rate" is whatever the car is designed to do.

.33 amps for a small refrigerator? Plus a phone charger and a laptop. Doing a "BIG 3" upgrade is way overkill. If it was me, I would install the battery isolator and use a deep cycle battery connected to your power inverter. You factory charging system would handle the additional load just fine. Most people that perform the "BIG 3" are running caps to power their sound system thumpers (A.K.A rust removers and loose panel(s) locators). Just saying, but it's your project, your call.

The little frig would be about 3 or 4 amps. But you are right, not a big load. I'm not doing anything extreme. Local Walmart recently had 4 gauge battery cables in a closeout basket for $1. I already had some copper lugs.

So I replaced the ground to engine block with 4 gauge. The shorter cable to the chassis (front bar over the radiator) I left alone, it was thick enough for that short distance. Just cleaned the contact bolt area.

On positive side, cable to starter looked already 4 gauge, or almost, so I used it. Just replaced the cable to alternator with 4 gauge. Left alone short cable to fuse box.

Used marine terminals, so just attached with the wing nuts.

Had to have something to do while the car is down awaiting a new coil from Amazon.