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Unread 02-11-2014, 08:13 PM   #121
idskot
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Sorry to bring a thread back from the dead, but does this upgrade work with a YJ?

Specifically a '91 4.0L

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Unread 03-26-2014, 10:30 AM   #122
D0T-C0M
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I know this is a slightly older thread but for a 160a swap on a 12v system with a alternator wire less than 5' in length you need a 4AWG wire going to the alternator and a 8AWG fusible link. Rule of thumb is the fusible link is sized 4 cable sizes less than the main wire.

Using a '10AWG fuselink'/'6AWG wires' is not recommended at 160A because of the higher conductor resistance which causes higher voltage drops and more IR losses. The reason why no one is running into problem is because they aren't loading their alternators to max output current often and for long durations. Also a higher capacity alternator will probably still run fine on stock OEM wires because there still is a large safety margin in the sizing of the OEM wires but if you put a IR camera on it you'll see the stock wires are producing a lot more heat and your pushing the insulation of the wires much more when pushing the alternator to its max current.

5' of 6AWG at 13.85v and 160A gives a voltage drop of about 0.63v
6" of 10AWG fusible link at 13.85v and 160A gives a voltage drop of 0.16v

Total voltage drop = 0.79v
Total power loss = 160 x 0.79v = 125w of heat being generated in the wires.

5' of 4AWG at 13.85v and 160A gives a voltage drop of about 0.40v
6" of 8AWG fusible link at 13.85v and 160A gives a voltage drop of 0.10v

Total voltage drop = 0.50v
Total power loss = 160 x 0.50v = 80w of heat being generated in the wires.
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Unread 03-26-2014, 12:25 PM   #123
Ironhead
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Quote:
Originally Posted by D0T-C0M View Post
I know this is a slightly older thread but for a 160a swap on a 12v system with a alternator wire less than 5' in length you need a 4AWG wire going to the alternator and a 8AWG fusible link. Rule of thumb is the fusible link is sized 4 cable sizes less than the main wire.
But then what's protecting the factory wiring harness? That's where the question lies and I will have my solution completed soon with plenty of pics
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Unread 03-26-2014, 12:26 PM   #124
D0T-C0M
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Note that there is no fuse between the battery and PDC so don't worry about increasing the conductor and fusible link size from the alternator to the PDC. Your factory harness is being protected by each of the circuits individual fuses in the PDC. The fusible link isn't protecting the PDC


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Unread 03-26-2014, 01:02 PM   #125
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Referring to the above schematic,

The fusible link will only protect the wiring between the battery/starter and alternator in the event of a short circuited alternator. There is probably no immediate hazard in running the stock smaller wire/fusible link but that pushing the alternator at the max current capacity of the alternator like when your winching will generate an increase temperature rise in the wires and fusible link. The battery is spec'd at 600 cranking amps which will melt the link easily if the alternator is shorted, at 160amps it won't melt but it will get warm. I have decided to increase the wire size from the alternator and fusible link to properly match the increase current capacity of the alternator because I use my winch often and sometimes for long durations, I don't want to worry about over heating my wires.

I also want to be able to draw more current from the battery terminal to feed my winch,offroad lights,compressor and inverter so I need to also increase the wire size from the battery to the PDC as well because much more current will be flowing in that direction when using the winch.
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Unread 03-26-2014, 03:00 PM   #126
Ironhead
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The thing is, the battery can handle a surge, where the factory wiring was set to be protected by a 10 awg fusible link
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Unread 03-26-2014, 03:01 PM   #127
D0T-C0M
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Respectfully, What factory wiring are you referring to?

I'm changing,
the factory wiring to the alternator to a #4AWG,
upping the fusible link to a #8AWG,
upping the wire from the battery to the PDC to a #4AWG,
and finally upping the 2 negative wires on the battery negative post to #4AWG wires

The increase in wire size to all the wires connected to the battery (except starter) is to allow the necessary current to flow from the battery make the fusible link melt before the wires in the case of a shorted alternator to ground. Note: The negative wire(s) at the battery also need to be matched to the alternator wire.


The fusible link is protecting the battery (power source) in case the alternator shorts, it isn't protecting the downstream loads of the PDC. Protection of the downstream loads belongs to each of the individual fuses in the PDC.
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Unread 03-26-2014, 05:31 PM   #128
D0T-C0M
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Here is all the wires you should change if your going to upgrade to a 160a. Probably easiest just to go to the scrap yard to get what you need. All #4 AWG for the wires and #8 AWG fusible link.

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Unread 03-27-2014, 07:02 AM   #129
Ironhead
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Note that there is no fuse between the battery and PDC so don't worry about increasing the conductor and fusible link size from the alternator to the PDC.
that is because it is in between the Alt and the PDC in the oem wiring. my plan is to run a new 4 awg cable from alt to battery, then 4 awg cables to a 10 awg fusible links from battery to pdc and secondary power panel. plus replacing all grounds and + for starter. i dont think there will be an issue either way, but I feel this way is safer while getting direct current to my winch and still keeping the factory fail safes.

by no means do i consider myself an expert in this area, but have done a lot of research on it. but its discussions like these that keep the knowledge level up and work out little things. from what i have found, there arent many full write ups on the topic and many dont understand DC systems, so carry on and lets see where it goes. my original plan was very similar to yours
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Unread 03-27-2014, 07:11 AM   #130
D0T-C0M
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Your changing the position of fusible link from the alternator wire and putting it between the battery and PDC?
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Unread 03-27-2014, 07:13 AM   #131
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yes, cause i am running the alt wire to the batt instead of the PDC
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Unread 03-27-2014, 07:17 AM   #132
D0T-C0M
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Quote:
Originally Posted by Ironhead View Post
that is because it is in between the Alt and the PDC in the oem wiring. my plan is to run a new 4 awg cable from alt to battery, then 4 awg cables to a 10 awg fusible links from battery to pdc and secondary power panel. plus replacing all grounds and + for starter. i dont think there will be an issue either way, but I feel this way is safer while getting direct current to my winch and still keeping the factory fail safes.

by no means do i consider myself an expert in this area, but have done a lot of research on it. but its discussions like these that keep the knowledge level up and work out little things. from what i have found, there arent many full write ups on the topic and many dont understand DC systems, so carry on and lets see where it goes. my original plan was very similar to yours
This is completely wrong and potentially very dangerous, If you do that and your alternator shorts you will have a high chance to catch fire.
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Unread 03-27-2014, 07:19 AM   #133
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This is completely wrong and potentially very dangerous, If you do that and your alternator shorts you are going to catch fire.
how is that? are you saying the battery will burn up and ignite?
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Unread 03-27-2014, 07:46 AM   #134
D0T-C0M
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Exactly , you've removed the protection to the alternator by connecting it directly to the battery. If the alternator shorts your going to have at least 600 amps going to ground and your battery and/or alternator could potentially catch fire and #4 cable isn't big enough to handle 600 amps either. Even worst if you have a larger battery or dual batteries where the fault current can be as high as 1000-1500 amps. Very bad idea.

From our discussion you seem to think the fusible link protects the PDC - IT ISN'T - The fusible link is there to remove the alternator from the circuit in case its shorts to ground. It has nothing to do with protecting the PDC. The fusible link needs to be sized so that it doesn't heat up beyond spec during full load current (160a), running a 10awg fusible link is too small, try touching it after you continuously winch hard for a couple minutes. Will it probably work sure is it 100% safe no. Just follow the diagram, the engineers know what they are doing, and you'll be safely protected.
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Unread 03-27-2014, 08:10 AM   #135
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makes perfect sense.

is there a reason the factory went to the PDC instead of the battery for the alt connection?
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