Question Regarding the Big 3

[na_rsx 10+ year member]

I know all i need to know about the big 3, the question i have is the fusing part. I know when you do the big 3, its typical put a fuse between the + alt and + battery. and you need another fuse that goes from the + battery to the back (to the amp).

Now instead of buying 2 seperate fuse holders and fuses, can i use this instead, it has 2 seperate fuses and looks like it would be much easier. I think it might be cheaper than buying 2, and easier to install.

Click to read more...

 

[InfinitePeace 10+ year member]

I posted this in the sticky, but I want more opinions.

I bought a 180a from Ohio General and they told me more than once, upgrade to the largest size of cable (Big 3) that you can for everything more or less EXCEPT the Alt to Batt Pos. They told me, which I confirmed multiple times, on a short run, 4awg (at least for upwards of 200a) is plenty and ideal; they don't recommend larger than that in that location because the size of the post on the alternator is too small to bind to the larger wire; ergo because of the size difference, the post on the alt heats up too much and can overheat it. That was their recommendation and I'm going to have the shop that is doing it for me talk to them and confirm with a detailed description of my specific engine.

The other interesting thing they said was do NOT fuse that wire. I confirmed this as well, DO NOT fuse this wire because if for some reason it does indeed blow, the alternator will no longer see the battery and think that it's dead, so it will kick into high gear and stay that way until it burns up because it will never see that battery again until you've changed that fuse, thus leaving you with a dead battery and a burnt out alternator.

Discuss.

 

[SHOemup233 10+ year member]

I posted this in the sticky, but I want more opinions.
I bought a 180a from Ohio General and they told me more than once, upgrade to the largest size of cable (Big 3) that you can for everything more or less EXCEPT the Alt to Batt Pos. They told me, which I confirmed multiple times, on a short run, 4awg (at least for upwards of 200a) is plenty and ideal; they don't recommend larger than that in that location because the size of the post on the alternator is too small to bind to the larger wire; ergo because of the size difference, the post on the alt heats up too much and can overheat it. That was their recommendation and I'm going to have the shop that is doing it for me talk to them and confirm with a detailed description of my specific engine.

The other interesting thing they said was do NOT fuse that wire. I confirmed this as well, DO NOT fuse this wire because if for some reason it does indeed blow, the alternator will no longer see the battery and think that it's dead, so it will kick into high gear and stay that way until it burns up because it will never see that battery again until you've changed that fuse, thus leaving you with a dead battery and a burnt out alternator.

Discuss.

Don't know what everyone will say. But if the 4awg part is true...well. Thats cool I guess. I'm doing the big 3 tomorrow or Friday when I put in my sub

 

[blackbonnie 5,000+ posts]

the only reason the fuse will blow is if something happens to your alt and it is putting out more then the recommended amps that the wire/fuse is rated it. you fuse it so if that happens the fuse blows and doesnt put any more harm on your electrical system by fring other wires and your battery from more then the rated amps. when the fuse blows, that breaks the circuit, and without your alt your vehicle isnt going to run. your vehicle cant just run off a battery, it needs the alt to keep it charged. if the alt isnt charging your car will not run. correct me if im wrong

 

[blackbonnie 5,000+ posts]

4 awg max current capacity is right around 150 amps. if you have a 200 amp alt, and you try and get your 200 amps out of it, it will burn up your wire because 4 guage is rated at a max current capacity of 150 amps.

 

[na_rsx 10+ year member]

no one has answered my question //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[InfinitePeace 10+ year member]

the only reason the fuse will blow is if something happens to your alt and it is putting out more then the recommended amps that the wire/fuse is rated it. you fuse it so if that happens the fuse blows and doesnt put any more harm on your electrical system by fring other wires and your battery from more then the rated amps. when the fuse blows, that breaks the circuit, and without your alt your vehicle isnt going to run. your vehicle cant just run off a battery, it needs the alt to keep it charged. if the alt isnt charging your car will not run. correct me if im wrong

Well, I believe it will, but not for long. That's kind of my point. If said fuse DID blow, something is very wrong, and really the only reason it might is a faulty/cheap/pos/failing alt OR, improper wiring that allowed the pos wire of alt to somehow be grounded... that said, if it blew, you wouldn't know until your car just died. On the contrary I guess one could say that either fate is no good in the even that did happen... however, since I'm not doing any of this myself and leaving it 100% in the hands of professionals, I'm going to let a shop change the alt as well as upgrade the wiring per the manufacturer of the alt's spec. That way, if ANYTHING does go wrong, I know exactly who to blame. But, I'm confident that if I allow professionals to do this, and do exactly as they say, that I won't have a problem.

 

[na_rsx 10+ year member]

 

[InfinitePeace 10+ year member]

4 awg max current capacity is right around 150 amps. if you have a 200 amp alt, and you try and get your 200 amps out of it, it will burn up your wire because 4 guage is rated at a max current capacity of 150 amps.

That of course then goes back to the binding post problem. Not to mention that when is that alternator in a normal install ever going to pushed to those limits when the majority of the demand is on the battery itself; the alternator's job is really just to keep it charged. No?

 

[blackbonnie 5,000+ posts]

but that is why your fuse the wire, so if something like that does happen, it only happens to the alt and not your battery and other electrical components

 

[blackbonnie 5,000+ posts]

That of course then goes back to the binding post problem. Not to mention that when is that alternator in a normal install ever going to pushed to those limits when the majority of the demand is on the battery itself; the alternator's job is really just to keep it charged. No?

then why upgrade your alt?

 

[InfinitePeace 10+ year member]

no one has answered my question //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

If you read carefully, we are answering your question. If my argument and the company that built my alternator are correct, you don't need or maybe even shouldnt fuse the alt pos --> batt pos wire. Therefore, you would just use a single inline fuse holder. However, if I'm wrong, I still would... because its just easier to use two inline fuses rather than try and route both of those wires through that block. IMO.

 

[na_rsx 10+ year member]

If you read carefully, we are answering your question. If my argument and the company that built my alternator are correct, you don't need or maybe even shouldnt fuse the alt pos --> batt pos wire. Therefore, you would just use a single inline fuse holder. However, if I'm wrong, I still would... because its just easier to use two inline fuses rather than try and route both of those wires through that block. IMO.

not really because this thread may prove you wrong

http://www.caraudio.com/forum/showthread.php?t=293818

 

[InfinitePeace 10+ year member]

then why upgrade your alt?

You know... I never thought of it that way. I don't know why that never occurred to me... I think maybe that given that argument, a HO alternator is going to put out a higher amperage at a lower RPM (engine) than a lesser unit. But you're right... if such is the case, what happens with an even larger alternator?

I'm going to call and ask them exactly that. I have to believe they know what they are talking about or they wouldn't have been in the alternator business for 30 years..

 

[InfinitePeace 10+ year member]

not really because this thread may prove you wrong
http://www.caraudio.com/forum/showthread.php?t=293818

Somehow, that wire had to have grounded out, or rubbed through the insulation because of a number of things that were mentioned. Yes, had it been fused it may not have happened like that, but the real kicker is why? Why did it happen? Find that answer, and the fuse or not is irrelevant, because it would not have been an issue.