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power wire size and fuze?

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=125932
Printed Date: March 28, 2024 at 12:34 PM


Topic: power wire size and fuze?

Posted By: rady449
Subject: power wire size and fuze?
Date Posted: January 30, 2011 at 11:00 AM

hi, i am currently putting together a system in my 96 ford explorer 5.0 and am planning on putting 2 12 alpine type x's with 2 ALPINE MRP-M2000 MONO 2000W RMS amplifiers (one for each sub)and i am wondering what u would recommend for wain power wire size and fuse from the 2 batteries under the hood to the 10 farad cap in the back.

the amplifiers both have 6 30amp fuses (180amps per 360amps for both) and your wiring guide says 1/0 is only good to 350amps. and what kinda fuse would i use, i cant find any bigger than 300.
there will also be an Alpine PDX-F4 4-Ch Class-D Amp 400 Watt Amplifier for the component speakers which has 2 30 amp fuses.
420 amp max draw. what u got fr me?



Replies:

Posted By: i am an idiot
Date Posted: January 30, 2011 at 6:02 PM
The sole purpose of the fuse under the hood is to protect the power wire and the vehicle.  As long as you do not fuse it beyond it's capacity all will be fine.  I see no reason you would need more than the 300 amp fuse. 




Posted By: rady449
Date Posted: January 30, 2011 at 7:16 PM
well what im saying is that if my amplifiers are going to draw a max of 420 amps do u think 1/0 gauge being rated for 350 will be a safe, suitable cable for the main power and ground? and if not would 2/0 marine cable work/be efficient?
and would'nt a 300 amp fuse blow under a 420 amp load? if so would i use a buss fuse...but they are rated for 45 volts and up, would that be safe?




Posted By: rady449
Date Posted: February 04, 2011 at 7:22 PM
new thoughts, what about running two power wires, one for each sub amp and putting the component amp on either circuit.
i wanna put 2 optima yellow tops under the hood, and a 250 amp alt. could i connect the batteries separately to the alt. and run a power off each one. and still ground them to the same point to prevent loops?




Posted By: silverbullet555
Date Posted: February 04, 2011 at 8:21 PM

You could run 2 0 gauge runs if you want, but both need to be fused. Or you could run 2/0. 3/0 or 4/0.  Considering how expense 1/0 is, you are getting up there and it's pretty pricey.

The real question is why are you running so many watts to speakers rated at 500-1000W RMS. You could wire both speakers to the same amp at a 1 ohm load, get 2000 watts out of the 1 amp and make your life a lot easier.



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James




Posted By: afdanw
Date Posted: February 04, 2011 at 9:29 PM

What i would do is run 2 sets of 1/0 into a distribution block.  then you can split off the distribution block into your 3 amps.  Fuse both lines coming off the battery to the Distribution block.  Also 400+ amps of current is a lot.  How many alternators are you running.  Even with the 250a alternator you mentitned, capacitors and yellow tops are not going to cut it, you need alternators for a set up like this (Alternators, as in probably 2 or 3 of them).  250a < 420a.  The problem is pretty obvious.  That set up will not work, and is pointless. 

silverbullet555 wrote:

The real question is why are you running so many watts to speakers rated at 500-1000W RMS. You could wire both speakers to the same amp at a 1 ohm load, get 2000 watts out of the 1 amp and make your life a lot easier.


I agree, that is a lot of power for the subs you are running. 



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If your cousin is such a good installer, and he will install anything for a 6 pack; why are you talking to me?




Posted By: KPierson
Date Posted: February 05, 2011 at 7:21 AM
A general rule of thumb is for the device to operate at 75% of the current of the fuse.

If the amp has a 180A fuse is should pull around 135A max.

That would make 270A for the sub amps and 45A for the smaller amp. You're smaller amp, power components, will never come close to pulling 45A.

I'm with i am an idiot - 300A fuse should be sufficient. Before going that route though I would make sure you could find a 350A fuse. A fuse rated above 12 or 24vdc isn't going to hurt anything.

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Kevin Pierson




Posted By: rady449
Date Posted: February 05, 2011 at 11:21 AM
silverbullet555: The real question is why are you running so many watts to speakers rated at 500-1000W RMS. You could wire both speakers to the same amp at a 1 ohm load, get 2000 watts out of the 1 amp and make your life a lot easier.

i know a few people that suggested i up the power to 1500 watts at 4ohms cause they used to run a pair of x's at those levels and they took it all day like a champ and if i wanted i could wire them to 2ohms for a comp. and the amps i have (MRP-mp2000) are not 1 ohm stable.
also, afdanw< a 250 amp alt. is constantly putting out while running (i believe) and between the charge held in the battery and the cap. it should be able to keep up with the audio draw that comes in bursts. i think.

KP. thank you, i see what ur saying and i do have access to large amp fuses that are 45 volt to 450 volt ratings, i just was unsure if it would create extra resistance to a 12-16 volt system.




Posted By: silverbullet555
Date Posted: February 05, 2011 at 2:41 PM

Rady,

sorry about that, I mis-quoted the website. It's 2000 watts at 2ohms.

I'm not sure how much benefit you would get by powering them at that level. Might try it with 1 amp and then add a second if need be.

But, that is your choice and I have never been known for taking the simple way out so I can understand where you are going.

As previously recommended, you could run 2 1/0 cables from the battery to a distro block and then split from there. I would probably do that before I went to 2/0 or 3/0 just because 1/0 is easier to work with and to run.  Don't forget to ground the same.

For the fuses, I like to run ANL fuses for my larger lines and mini-anl for my smaller ones. The only thing I do is make sure my fuses are consistent by type so if I have a problem with a fuse I don't have to carry different types, just different ratings. You can find ANL ratings up to 400 amps plus. They are also used in forklifts which are battery powered so they come in larger sizes.



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James




Posted By: rady449
Date Posted: February 05, 2011 at 4:19 PM
well thank you much for the input, i will try one amp first but i have 2 already so more than likely i will end up with two cause i want to push some serious spl and i dont want to cause the amp to clip.

and ya i have all anl fuses, i just like them better than aug (more or less). on the subject of 2/0 cable, i have been unable to find any with a high count small strand construction of pure copper. do u have any sites, or recommendations?

also with 2 1/0 lines run to a dist. block, how would u wire in the cap? and would i use 2 1/0 grounds from the frame to the dist. block? i only ask cause it will be such a short piece of wire (under 1 foot)




Posted By: oldspark
Date Posted: February 05, 2011 at 5:01 PM
You should out that batteries as close as possible to the amp(s) - they should really be in place of the cap. Having long transmission between the batts & amps can compromise the AGM's low resistance (which is why they usually recommend AGM - aside from "internally housed" legalities & considerations).


Optima Jim from Optima reckons "you can parallel Optima batteries" (ie, yellow tops) - mind you, he didn't think it effected their reliability! posted_image & LOL!

I agree that you can parallel (any) batteries, BUT, if you want them to last.....
But you can search my posts for that.
(I presume you'd want to run the standard cranking battery up front and 2 yellows (or beer batteries) in the rear. Hence you probably just need one small-standard relay ($3?) plus two ~400A or 500A relays ($20-$30?) for automatic isolation. Then the normal fuses or breakers at each interconnection end etc.)




Posted By: silverbullet555
Date Posted: February 05, 2011 at 8:01 PM

For 2/0 cable you might try welding cable. It won't be as flexible as high strand count, but it should work. The insulation is generally really good and strong since it is designed to be used in a work environment.

I don't know how you would wire in the cap given what you are doing. If it were me and I was going to use a 2 amp set up I would probably use 2 caps. I would run one on each line for the sub amps and put them in after the distro block. again, I have never used caps so I don't know the ins and outs or what things you have to watch for.

For ground, you just want to match grounds with power wire. Electricity makes a loop which means what travels through the power wire has to travel through the ground so ground should be the same size as power.



-------------
James




Posted By: rady449
Date Posted: February 06, 2011 at 12:05 PM
ok thanks guys.

old spark: i have been reading that i would be better off putting the batteries under the hood cause they charge better in the heat? but i agree with you that i would like to put them in the back with the amps. but i dont know how/where to wire in the relays. can u give me a page or vid to look at?




Posted By: oldspark
Date Posted: February 06, 2011 at 3:38 PM
What the heck have you been reading?

Put them in a fire - they'll have even greater capacity - you don't even have to charge them!

Heat destroys batteries! (As with most things.) What's the rule = half the life for ever 10 or 15 degree C (~18F - 27F) increase?


And why is "better charging" so important (not that I am saying heat means "better" charging)? What is wrong with normal charging?


Finally, since you have the extra cable (incl ground) resistance from the hood to the trunk/boot, how does that compare to the resistance gain of using AGMs in the first place? Why bother even using AGMs - wet cell will handle the hood heat much better than AGMs, and probably cost well under half as much, and probably with negligible audio performance loss (as I said - what is the extra cable resistance?).




Posted By: rady449
Date Posted: February 06, 2011 at 4:05 PM
i read that having batteries in ur trunk at a much lower temp than under the hood will cause there rate of recharge to be slower. i read that on car audio magazines website. and the reason i will use dry cells is cause they can handle drain and recharge something like 8 times better than wet cells. so i have also read. and they have lower internal resistance which allows for a faster charge and discharge rate.not to mention they can be mounted any way to fit better and they are not likely to be affected by vibration.




Posted By: oldspark
Date Posted: February 07, 2011 at 12:48 AM
rady449 wrote:

i read that on car audio magazines website

So they are suable for misleading information....
I suspect they are into money generation and supporting their industry. Else the contributors think they know it all (like the "the voltage is 14.4V BEFORE it passes thru the voltage regulator, thereafter it is 13.8V"... sorry dude, a car's voltage supply does NOT pass thru a voltage regulator! And it is often above 13.8 etc...)

Read elsewhere.
Heat generally increases the resistance of things so why heat up a battery?

Rate of recharge slows with temp?
Why is recharge a concern - when would you need to recharge them that quick?
And if a battery is hot, don't you have to slow the recharge rate? Optima specify 50C/125F as one of their recharge temp limits...

EIGHT times better? How? Usually AGMs are only HALF the resistance or flooded cells. (Maybe they quote 10 year old flat batteries???)
And they are saying you can pump a higher current into an AGM? An AGM has no liquid to boil off to keep cool. I think you will find "quick charged" wet cells last far longer than AGMs!

How are wet cells effected by vibration? Mine vibrate all the time! Not to mention my 4-wheel jumps etc.

But yes, internal "non-vented" mountings and any angle (except upsidedown for some) is a reason AGMs are chosen - but that should be irrelevant in a engine bay.


Maybe you could check some of those details at batteryfaq.org or one of its references/links.


I'll let you decide what you want to trust.
I've seen enough audio forums recommend batteries rather than a properly sized alternator or that lower-ohmage speakers are better to last me a while.
Many still spruik capacitors (despite the guy that pioneered caps subsequently condemn their use!). And recently I've seen gems like "100AH per 1,000W" for battery sizing!   

It's Frank Zappa's Flakes all over again! (Gotta love a free but expensive market eh?)




Posted By: rady449
Date Posted: February 07, 2011 at 6:30 PM
u know u are probably right, thats y i made an account here and started asking, cause i have been i love with quality car audio fr like 8 years now but only in the last year have i really started to reserch the facts about how to produce it cause the crap the local stores feed me has repetedly failed. and thank you for the link:) what do u think about putting one large batteri in the back, like 200amp per hour discharge. or would that really only be for playing without running the vehicle.




Posted By: oldspark
Date Posted: February 07, 2011 at 11:00 PM
Firstly, I asked an "audio" guy where I work if he had ever heard of anything (so ridiculous....).
Once thru a common usual rap of "there ain't dry cells - only gels" (wrong!!), he greed crap, heat is bad etc.
He added how he only had one (extra; dry-cell) battery in the boot.
Also that if your 2nd bateries die, that's because they are powering jackhammers which are this high & .... (Sound comps etc.)


So hence secondly, battery sizing depends on the peak thump etc.
(Oddly enough he said drys/AGMs handle it all - despite the jackhammer failures - but the point is that flooded cells have double the impedance therefore limiting their current and therefore they usually do withstand such hammering!)

It's a case of overall design.
Is the alternator big enough to handle the load?
If it handles full load RMS, then you probably won't need batteries because the double (and higher) peak output of an alternator is equivalent to having a battery or cap.

If sound dips are due to high current/resistance from the alternator (& main battery) to the rear mounted amp, then a battery is mounted next to the amp. (Else a cap if you can't afford a $20 AGM!)

If undersized alternators are the issue - meaning that your batteries discharge during audio use - then battery size depends on how long for and what magnitude - ie, AH rating. (The same as for "reserve time" - playing time without charging.)
Remember that the LESSER current a battery is discharged at, the LESS the discharge amount (depth), the SLOWER is is recharged (ie, longer with less current) and the LESS OFTEN it is recharged, the longer it will last.

BTW - batteries HALVE their life for every 10C/18F increase, so under the hood, you might replace your yellow tops 4 times as often as being mounted in the trunk; maybe 8 or 16 times as often as being vented from the cabin.    


Thanks for the compliments...

The problem with audio forums is that many use an isolated i of data or fact without appreciating the overall picture. EG - instead of mounting in the engine bay, spend 25% extra on capacity and save $300 on ongoing expenses!
And as I said, what about the increased voltage dip due to the remote battery, or increased resistance from temperature? (They do know that quoted battery resistances are ONLY for fully charged batteries? Resistance increases as they discharge.)
And no mention of voltage compensation for said temperature changes....




Posted By: rady449
Date Posted: February 08, 2011 at 10:02 PM
ok so what would u say about this....i wanna add a 250 amp alt. and connect 2, 1/0 power wires to go to individual optima yellow tops, then through there own 10 farad cap and then to the 180 amp 2000 watt amps. all grounded to the same point. and the component amp i was going to connect on the cranking amp under the hood that will still be charged off the stock 130 amp alt. also grounding the amp to the same point





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