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Old 02-16-2005, 12:39 PM   #1
mvorchard
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Question Planning the Big Three

Hi again,

I'm planning on doing the Big Three upgrade together with the rest of my installation next week (eD NINe.2, plus VGA 500.4 bi-amping fronts).

I'm a little confused on what fuse to use in the 'alternator to battery' section. Chris says
Quote:
The fuse should be sized to match the max ampacity of your wire, not the output capability of your alternator.
but I'm just not sure on what the "ampacity" of a 4 awg wire would be. Any clue??

Second question: is 4awg wire thick enough?? How much should I get? 10 feet??

Are there pictures out there of your upgrades? I guess a couple of you have already done it!


Thanks,

MO
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Old 02-16-2005, 01:12 PM   #2
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www.BCAE1.com
section 14. Fuses

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Old 02-16-2005, 01:15 PM   #3
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To actually directly answer your question though, the max recommended for 4awg is a fuse rated at 125A. 4awg is thick enough. And I would get at least 15ft as it is cheap and you don't want to worry about making things too exact. Besides left over wire can always be handy. I haven't done the Big 3 yet for my Subie so I don't have any pics myself.

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Old 02-16-2005, 01:26 PM   #4
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As always, BCAE had the answer..... I even had a window with it opened.... thanks!!

I'm trying to get it locally; as it is heavy, it is one of the expensive things to bring over from the US to Chile - several times its own value...


Thanks again!
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Old 02-16-2005, 01:34 PM   #5
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Quote:
Originally Posted by mvorchard
I'm trying to get it locally; as it is heavy, it is one of the expensive things to bring over from the US to Chile - several times its own value...
I always forget you are from Chile. I doubt it would ever help, but if you need something shipped from a non-business address or something let me know.

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Old 02-16-2005, 01:39 PM   #6
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Many thanks for that kind offer. You never know.......


Cheers,

MO
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Old 02-16-2005, 02:05 PM   #7
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Question AGU vs ANL...

Hi again,

I cannot find AGU fuses of more than 100 amps........ any advice???

And if I look at ANL fuses (I don't want to, ANL fuse holder is $20!!), they seem to rapidly jump to 150... and fuses are $10 or $15!

Any (good) advice???? Pleeeease.


Thanks,

MO
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Old 02-16-2005, 02:17 PM   #8
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For that large a fuse its gonna cost a few bucks

part no 071-950 and 263-692 at www.partsexpress.com are under 25$.

But one thing I am confused on. Are you adding a fuse to the ground between the alternator and battery? I ask because you mention doing the big three.
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Old 02-16-2005, 02:21 PM   #9
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I'm realizing it....... thanks Bryan. And yes, 'alternator to battery positive' section within the Big Three needs a fuse.
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Old 02-16-2005, 02:23 PM   #10
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If I only find 100 amp ANL fuses, it doesn't make much sense going for ANL.... as 100 amps AGU fuses are out there, does it????
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Old 02-16-2005, 02:25 PM   #11
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As long as you never need larger than 100 its OK....but if you need more than 100amps out of our stock alternator something wrong with it.
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Old 02-16-2005, 02:28 PM   #12
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I get it, but... there is no 125 amps fuse out there (at least I have not found!), and I cannot jump over to 150, as it'd be exceeding 4awg "ampacity".

I guess I won't be needing more than 100..... would I????
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Old 02-16-2005, 02:32 PM   #13
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So is this the same as a grounding kit?
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Old 02-16-2005, 02:38 PM   #14
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not unless you change the alternator.

its part of it
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Old 02-16-2005, 02:47 PM   #15
mvorchard
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I've just found a 125amp ANL fuse, and I'm also ordering a ANL fuse holder from Knu....

Will let you know what happens!


Cheers,

MO
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Old 02-17-2005, 02:01 PM   #16
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OK. I've ordered everything I need; won't be cheap, but well.......

- Stinger ANL Style Gold Plated Fuse 125 Amp (from eBay)
- 16 feet of Knu 4 Gauge Purple Power Wire
- 1 x Knu In-Line Waterproof ANL Fuse Holder Blue
- 6 x Knu Gold Plated 4AWG Ring Terminal Blue

It should (I hope!) get here by next week, before my project starts... but is not a problem if not, as I'm actually planning to do the Big Three the last upgrade; only after everything is reinstalled


Cheers,

MO

Last edited by mvorchard; 11-28-2005 at 03:48 PM. Reason: spelling
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Old 02-17-2005, 03:22 PM   #17
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Don't forget that you still have the stock 80a or so fuse off the main alt-bat wire that runs through the fuse box.

I fused my 150a alternator @ 100a with 4gauge using an ANL fuse.

I think 100a there would be plenty, esp with an 80a reserve path...

I'll take a pic of my setup and post tonight.

-- Dave
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Old 02-17-2005, 03:35 PM   #18
Farfrumwork
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yeah, please post a pic!!

I am curious about this "big three" dealio. I assume it is an upgraded alternator, along with necessary wiring (?) - right?

Where are you guys getting high output alt's? I would like one as I run an A/W intercooler pump (on constantly) and am planning on installing a smallish sub someday and some fog lights (all with my underdrive pulley in-place).

So the stock alt is a 60amp? and you are upgrading to a 100 or 150amp?

(oh yeah, I did search for big 3 with little result )

thanks!
Chad

Last edited by Farfrumwork; 02-17-2005 at 03:36 PM. Reason: yes I did search
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Old 02-17-2005, 03:44 PM   #19
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I'm running a 150a alternator because I push over 600w rms, plus all car accessories and I cooked my stock alternator in a year and a half.
Quote:
Originally Posted by Farfrumwork
(oh yeah, I did search for big 3 with little result )
Did you click the Big Three link in the first post?

My only issue with that link is that they used the main battery to body ground as the one that went to the frame support that runs over the headlights. This is a poor ground. You should ground the [-] terminal of the battery up to the firewall/bedpan of the car. This is normaly one large stamped sheet of metal and makes a great grounding plane. My amps are gounded to it back in the trunk (using seat bolts).

-- Dave

Last edited by AcquaCow; 02-17-2005 at 03:50 PM.
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Old 02-17-2005, 05:50 PM   #20
mvorchard
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Quote:
Originally Posted by AcquaCow
Don't forget that you still have the stock 80a or so fuse off the main alt-bat wire that runs through the fuse box.
Don't quite get it..... what should I do with that extra fuse??

Quote:
I fused my 150a alternator @ 100a with 4gauge using an ANL fuse.

I think 100a there would be plenty, esp with an 80a reserve path...
Reserve path?? Please explain it a little further....

Quote:
I'll take a pic of my setup and post tonight.

-- Dave
Thanks man!
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Old 02-17-2005, 05:55 PM   #21
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Quote:
Originally Posted by AcquaCow
I'm running a 150a alternator because I push over 600w rms, plus all car accessories and I cooked my stock alternator in a year and a half.
So........... with a VGA 500.4 throwing 375 rms (because of my Focal tweeters), and a NINe.2 putting 400 rms bridged....... WWHHAATT is going to happen to my alternator???

Do I need something special? Do I need to think of another alternator right now??

Quote:
Did you click the Big Three link in the first post?

My only issue with that link is that they used the main battery to body ground as the one that went to the frame support that runs over the headlights. This is a poor ground. You should ground the [-] terminal of the battery up to the firewall/bedpan of the car. This is normaly one large stamped sheet of metal and makes a great grounding plane. My amps are gounded to it back in the trunk (using seat bolts).

-- Dave
I've just added your comment to the instructions I'm briefing to my installer - Big Three is scheduled for next saturday

Thanks again!

MO
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Old 02-17-2005, 06:07 PM   #22
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haha - no I did not see the link up front - haha

Thank You

(slinking into the background now.....)
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Old 02-17-2005, 08:30 PM   #23
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I actually didn't have a pic of the install like I thought I did, so I'll take one tomorrow in the sun.

As for the reserve path and the stock fuse...
Leave the stock wiring in place. Electricity will follow the path of LEAST resistance, it flows like water. If you approach the capacity of one fuse, the electricity will follow the other wiring path instead. with a 100a and an 80a fuse on 2 separate wires connecting the same two points, you have the ability to run 180a across it, just not 180a across a single fuse or wire.

If you push enough power and run with enough bass to get your lights to dim a good bit, you may want to consider reserving money for an alternator some day down the road. You may even want to connect an amp meter up behind your battery to see just how much juice you're using with your system running.

I've heard that with the headlights/fogs/fan/etc all turned on, you can pull about 70a out of the battery. As the stock alternator only puts out about 75-90a, that only leaves your stereo about 20 amps to work with.

Alternators don't always run at 100% output, but if you hook up a large enough load, they will run at 100% duty cycle and you will eventually cook the diodes in the alt. In my case, I think I fried the voltage rectifier. The alt eventually couldn't produce the current needed to run everything in my car, so it started upping the voltage. Once I saw it start climbing over 14v, I watched it very closely. One day I saw 16.5v out of it, that was the day I ordered the new alternator =P

Wow, that was long...

-- Dave
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Old 02-17-2005, 09:37 PM   #24
mvorchard
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Dave,

Thanks much for this small writeup

Hopefully, it will last for a few months... as I'm planning on replacing my car before the end of the year...

If I'm not measuring anything, how would I know of a problem in/at the alternator?? Any particular syntom I need to look for?? How much is a new (better?) alternator?

Thanks again.


Cheers,

MO
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Old 02-17-2005, 10:10 PM   #25
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When my alternator started failing, the BRAKE and BATTERY lights on my console would flicker every now and then. That seems to be the ECU's method of telling you that your charging system is going bad. After that starts happening, you've got a few months before it finally gives up.

I wouldn't worry about it until that starts happening.

My 150a alt cost me $270. You can pick up used wrx alternators for a LOT cheaper though.

You can probably get 2 years out of your stock alternator if you have a good battery and upgraded lines. I didn't have a good battery or any wiring upgrades when my alt died. I do now.

-- Dave
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