I just spun myself out on this, I feel like I know the answer but fuck it

If i'm running an amp that draws 400a rms, and I have a 200a alt, a g31 under the hood 4/0 to the rear bank, and 6 g31's in the rear, I fuse appropriate for the wire always, not the peak rating of my alternator yes? something like, 300a for 4/0 iirc. 

If I already plug up the bank and charge it fairly often (once a week), no real concern for such a small alt supporting that bank, correct?

 

If you have a amp that draws 400amps you need a 400amp fuse. 300 may blow at peak if your amp actually draws 400 for any period of time. I doubt it ever would but usually amp manufacturers suggest a 100amp fuse for every 1k watts. I am using a 100amp fuse on a HD1200 and have never blew a fuse but some less efficient amps will blow fuses that are a little small if they draw to much current for to long. 

Are you looking to fuse to keep the amps safe or just to protect against the wire shorting to ground from the front battery to the rear?

If it's from the front battery, I'd fuse for the wire (as you said).

In the rear, to the amp. I'd fuse for the amp.

you fuse for the wire. if the draw over that wire is higher then the wire is rated for you need more wire not more fuse. 

My confusion is, if the bank is between the amp and the alt, the amp will draw from the bank making only one run of wire necessary as far as the charging system, correct? Therefore, I fuse that single run to protect from shorts, yes? No need to worry about smoking my alt with a fuse larger than it's output capacity, letting me just wail on it?

Edited November 13, 20168 yr by SpeakerBoy

Sorry, what is confusing?

Simply don't over fuse the wire.  The rest follows.  ie, size the wire appropriately for your install and then fuse as well.  The caveat of course is that you can always use a smaller fuse than the wire requires, but never the other way.

14 hours ago, lithium said:

you fuse for the wire. if the draw over that wire is higher then the wire is rated for you need more wire not more fuse. 

 

4 hours ago, ///M5 said:

Sorry, what is confusing?

Simply don't over fuse the wire.  The rest follows.  ie, size the wire appropriately for your install and then fuse as well.  The caveat of course is that you can always use a smaller fuse than the wire requires, but never the other way.

This

Guess I was paranoid about my alt being allowed to run wide open like that but I've never had <12.6 so I think I that means I'm okay for the time being. 

 

Thanks guys. Like I said, overthought lol.

1 hour ago, SpeakerBoy said:

Guess I was paranoid about my alt being allowed to run wide open like that but I've never had <12.6 so I think I that means I'm okay for the time being. 

 

Thanks guys. Like I said, overthought lol.

The fuse has nothing to do with how hard your alternator runs, that's the job of the voltage regulator in older cars, and the pcm in newer cars. Basically the alt does what the regulator, or pcm,tells it to do. If the pcm see's low voltage, it will demand more out of the alt, and when it see's a resting 14.4volts, it will make it run just enough to keep a steady voltage. All fuses are for, is a safe guard against shorts, or voltage spikes, so nothing catches fire, they don't restrict, or control anything except braking the chain of juice, if to much is traveling through them. 

Edited November 13, 20168 yr by Billy Jack

22 minutes ago, Billy Jack said:

The fuse has nothing to do with how hard your alternator runs, that's the job of the voltage regulator in older cars, and the pcm in newer cars. Basically the alt does what the regulator, or pcm,tells it to do. If the pcm see's low voltage, it will demand more out of the alt, and when it see's a resting 14.4volts, it will make it run just enough to keep a steady voltage. All fuses are for, is a safe guard against shorts, or voltage spikes, so nothing catches fire, they don't restrict, or control anything except braking the chain of juice, if to much is traveling through them. 

Shorts definitely, voltage spikes not so much. The fuse cares less about the voltage applied but it is affected by the current flowing through it. 

I don't know how my alt is controlled, but I know how a fuse works.

I'm not confused anymore lol, I had a derp moment trying to figure out if I needed a smaller fuse because my alt is the choke point in the charging system.

3 hours ago, SpeakerBoy said:

I don't know how my alt is controlled, but I know how a fuse works.

I'm not confused anymore lol, I had a derp moment trying to figure out if I needed a smaller fuse because my alt is the choke point in the charging system.

We all have those moments, it get even worse as you get older. I forget stuff I have known for years, and later realize, duh I knew that, why couldn't I remember it. But I have had a butt load of concussions, so it's could be either, or both, for me. I had amnesia in the mid 2000's, that's the weirdest shit ever, I knew my name, but had 5 years of my life just gone, I have picked up a few major things, but for the most part that 5 years is gone. Sorry if I'm off topic, but you did bring up durp moments.