size of fuse for 1/0 awg?

Okay, so I recently purchased 20' of KnuKonceptz 1/0 wire, to replace the old 4 awg wire that runs from the battery to the trunk. My question is if the 150A ANL fuse I have for it will be sufficient for the 1/0 wire as well. Or do I need to upgrade fuse sizes? I'm pulling around 1400 wrms(total system power), so I was thinking that I might need to upgrade to a 200 or 250 A  ANL fuse. Any recommendations or suggestions? THanx guysSoldier: This is the worst part. The calm before the battle.

Fry: And then the battle is not so bad?

Soldier: Oh, right. I forgot about the battle.

u should be fine with 150 amp fuse if u are pullin 1400 watts rms... maybe upgrade to 200 amps if u wanna improve.....i ususally equate every 100 watts to about 10 amps..... it's simple and easy to remember.... but hey.... there are alotta other factors to put into the mix... what amps are u using.. did u do the big 3 upgrades yet... what kind of car is it..... more info... and u will receive more informative answers........there can be only one.......

You should be fine with the 150A because you won't pull over 150A with 1400w. 1400w output means 1750w input for 80% efficient amp (class D). 1750w/14.4 = 122A. Even if you only had 12V, 1750w/12V = 145A. Just use the 150A and if you blow it you can safely go all the way up to a 350A fuse.

350A. Whatever the power or load you are connecting to the far end, you are putting that fuse in place to protect that power wire and the car anyway, it is NOT EVER rated or sized to protect the amplifier. If you have installed a 1/0 power cable, you will install a 350A fuse. Ask yourself this: if you only NEED 145A, then why are you wasting money on a 350A cable when all you need is a 150A cable? A #4 is perfectly safe at the current level.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

I figured that 4 AWG would suffice, but while the car is at idle, my cap is dropping from 12 to 10 volts on hard extended bass notes. I have done two of the big three (the negative ones) with the same 4 AWG wire. The amps are kicker zx1000.1 and zx350.4, and the car is an 06 toyota corolla.Soldier: This is the worst part. The calm before the battle.

Fry: And then the battle is not so bad?

Soldier: Oh, right. I forgot about the battle.

another thing too... due to the rising price of precious metals....ie; copper and nickel.... a lot of companies out there are skimping people on the wire in the power kit..... on the outside....u see what appears to be the advertised wire... on the inside..... u might have only gotten a third of what u paid for..... that may be why it only had a 150 amp fuse..... u may have gotten 4 guage in a 0/1 guage coating..... at the shop i work at we see a lot of this from customers who order wire on line or buy it at a flea market...... good reputable wire is normally from streetwires.. tsunami.... kicker..... etc....... jl wire is not bad too.. we sell a lot of it...there can be only one.......

haemphyst wrote: 350A. Whatever the power or load you are connecting to the far end, you are putting that fuse in place to protect that power wire and the car anyway, it is NOT EVER rated or sized to protect the amplifier. If you have installed a 1/0 power cable, you will install a 350A fuse.

I completely disagree with this statement.  Fuses are a safety device and you shouldn't use a bigger fuse then you actually need.  The 350A number you list should be the absolute MAX fuse size, but shouldn't be factored in if a smaller fuse can be used. 

If you can get away with a 150A fuse then use the 150A fuse.  If the power wire shorts out what would you rather subject your cars electrical system to - a 350A short or a 150A short?  That extra 200A (which, in reality would even be more since fuses are rated to blow based on a % of actual fuse size) of current during a short could be enough to damage ECUs/PCMs/TCMs/BCMs/etc.  The bottom line here is that the 150A fuse will protect his wire/car more efficiently then the 350A fuse and provide no negative effects what so ever.

The size of the fuse will NOT limit current.  Increasing fuse size will not improve anything. 

haemphyst wrote: Ask yourself this: if you only NEED 145A, then why are you wasting money on a 350A cable when all you need is a 150A cable? A #4 is perfectly safe at the current level.

This is the real question here.  1/0 is total overkill and not needed.  It won't fix his problem, which is most likely caused from the fact his electrical system simply can't keep up with the demands of the additional '1400 watt' load.

Kevin Pierson

KPierson wrote: The size of the fuse will NOT limit current.  Increasing fuse size will not improve anything.

And I have to disagree with THIS statement... The very reason a fuse heats up and melts, (and opens the circuit) is BECAUSE it is limiting the current. The minimal voltage drop, and associated current limiting (for example - 150A) EQUALS the dissipation of energy (heat) within the fuse element, causing it to melt! Fuses CAN limit current as they reach their nominal currrent rating. They have resistances in them, and just like ANY resistance, it WILL cause a current loss.

klctexas wrote: I figured that 4 AWG would suffice, but while the car is at idle, my cap is dropping from 12 to 10 volts on hard extended bass notes. I have done two of the big three (the negative ones) with the same 4 AWG wire. The amps are kicker zx1000.1 and zx350.4, and the car is an 06 toyota corolla.

Then that means you don't have enough alternator, NOT that you don't have enough power cable. Additionally, just because you have a 1/0 POWER cable, you are still using the effective current carrying capability of a #4, because you have not swapped out ALL of your cables. Where does the current go? It returns through the ground to the battery. If the return in only a #4, you can't shove more current down it, just because you have a big fat positive cable, can you? No. You have to upgrade EVERYTHING, and that includes your alternator, as we have already determined that it is too small. Oh, and I might add this. If your return (the ground) is a #4, then in that case, YES! YOU WILL ONLY FUSE FOR THE SMALLEST CURRENT CARRYING CONDUCTOR IN THE CIRCUIT!!! 150A, in this case.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

haemphyst wrote: KPierson wrote: The size of the fuse will NOT limit current.  Increasing fuse size will not improve anything. And I have to disagree with THIS statement... The very reason a fuse heats up and melts, (and opens the circuit) is BECAUSE it is limiting the current. The minimal voltage drop, and associated current limiting (for example - 150A) EQUALS the dissipation of energy (heat) within the fuse element, causing it to melt! Fuses CAN limit current as they reach their nominal currrent rating. They have resistances in them, and just like ANY resistance, it WILL cause a current loss. [

Most (if not all) fuses will be fine at 100% load with minimal resistance change.  If you take a look at a data sheet for a quality fuse I think you'll be surprised.  http://www.cooperbussmann.com/library/bifs/2024.PDF

For instance, a 150A FAST blow fuse won't even start to fail until 250A or so.  At 250A it will still take ~100 seconds to blow the fuse.  That 350A fuse you recomend won't start to fail until >600A!

The point of this illustration is to show that fuses are DESIGNED to provide minimal resistance to the load UP TO the rating of the fuse.  What is the point of using a 150A fuse if it limits the current going through it to 125A?  In fact, the resistance change from 0 load to full load is so insignificant that they don't even include the resistance table in the data sheet!  If there was significant change it WOULD be listed on the data sheet as engineers would need this information to make fuse selections.

Another problem with using excessively large fuses, like you recomended here, is that the instantanious current available by the battery may not exceed the current required to blow the fuse quickly.  That 350A fuse needs to see 700A for 5 seconds to blow.  In a car with a smaller battery with a fault detection alternator it is possible that the battery will short out to the point of explosion before the fuse actually blows!  I realize this is far fetched, but it is possible.

It is general practice with SMALL wires to always fuse/protect to the maximum current that the wire can dissapait, but as the wire and current gets bigger and bigger its a different story.  With smaller wire a difference of 10A isn't a big deal, but with bigger wires 150A CAN be the difference between blowing a fuse in time or shorting out the battery long enough to destroy every electronic part in the car..

Kevin Pierson