250a fuse on 220 amp alt

[xpl0it 10+ year member]

On my wire coming from my alt to my batt, i have a 250 amp fuse just before the battery. What happens if this fuse pops while I'm driving? Will my power steering, breaks, and all turn off?

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[psych0ticnemes1 5,000+ posts]

On my wire coming from my alt to my batt, i have a 250 amp fuse just before the battery. What happens if this fuse pops while I'm driving? Will my power steering, breaks, and all turn off?

you still have the original wire there, so i wouldn't think so

 

[yacob.naif 10+ year member]

no, your car runs on the battery, the alternator simply charges the battery

and unless you have a 2002+ bmw, all those things you mentioned are vacuum/accessory belt driven

your battery light will come on, and you'll find a suitable place to pull over and change your fuse

 

[xpl0it 10+ year member]

Yeah true, but wouldn't that original wire catch fire then?! Maybe I should disconnect the original wire! I never even thought about that, if my fuse pops, then my original wire which is like 8 gauge will try to transfer 220 amps, oh shit.

 

[mikeyboc 10+ year member]

Wouldn't the size of the original wire alone create a big problem? I remember when I bought my HO alt, they said not to install it until the alt to batt wire was upgraded. Might be wrong though.

 

[yacob.naif 10+ year member]

That's why i removed my factory alt-to-batt cable, i wanted to know if something was amok, diagnosing a 1/2 a$$ problem's a lot harder to diagnose than when something's completely not working

If you need to leave the factory cable for whatever reason, i'd get a fuseholder with an alarm, so you know if it's popped, you don't wanna be forcing all that current through your factory wire.

 

[xpl0it 10+ year member]

Yeah or I could just disconnect the factory wire at hte alternator and put a rubber hose over the end of it. Also, my 1/0 stinger expert series from my alt to batt follows the original factory wire but it runs right through the engine area where it's hot and my wire was pretty hot, not too hot to touch though. I just don't want my wire melting, shoudl I put a plastic hose on there?

 

[yacob.naif 10+ year member]

No, the plastic will get hotter than the silicone and melt...... And then the temperature of the melted plastic is prob. gonna be what melts through your wire.

Most exhaust parts in your actual engine bay have heat shields over them anyways, just look at all the wires running around in your engine bay from the factory.

Only time i ever had a problem with wires MELTING was running a 2ga. battery relocation kit under the car in my jetta, cause i was too lazy to pull the trim panels apart... It scooted itself over to the exhaust pipe, and the whole car filled with smoke, and my car shut off.

THAT was scary.

 

[xpl0it 10+ year member]

I doubt a 250 amp fuse will pop though, that would require like 300-315 amps of juice.

 

[xpl0it 10+ year member]

Wouldn't the size of the original wire alone create a big problem? I remember when I bought my HO alt, they said not to install it until the alt to batt wire was upgraded. Might be wrong though.

i have (1) 1/0 gauge going from alt to batt as well as (1) 8 gauge going from alt to batt, but as we all know, current passes through the least resistant wire (1/0) so the 8 guage is barely seeing any current pass through it at all.

 

[yacob.naif 10+ year member]

There was a thread not too long ago about car fuses, the end consensus was that car audio 200A fuses pop right at 200, and 250A fuses pop at 250, they're not like home fuses where there's a leniancy.

So get one that's the same output as your alternator, just in case that wire DOES decide to break...... Probably wouldn't damage anything down there, but it would probably kill your battery, and make it an expensive trip home.

And ^^ about amperage, the fuse is to protect your batt, not your alt, it's to keep your entire battery from discharging when it grounds out to your engine bay.

 

[bamaboy 5,000+ posts]

some alts can put out more than they say

 

[mikeyboc 10+ year member]

i have (1) 1/0 gauge going from alt to batt as well as (1) 8 gauge going from alt to batt, but as we all know, current passes through the least resistant wire (1/0) so the 8 guage is barely seeing any current pass through it at all.

That's exactly my point. If the fuse between the alt and batt pops, then the only path for the current is the 8 ga stock wiring, which could result in some major problems (I would think) depending on the length of run and some other factors.

 

[singlesubsetup 10+ year member]

so now there's a need to fuse the wire between the alt and the battery? where is this comming from and where is the links to this? If your alternator wire is rated for your alternator, why do you need a fuse?

if you have a 200 amp alternator and upgrade your wire to 1/0 gauge and your sysem pulls lets say 400 amps, the rest of the power comes from your batteries.... Are you saying the extra draw (400 amps) will cause your alternator wire to melt? someone please explain this to me so I can understand..