3900 watts rms

[ti09ny]

i was wondering if i ran 3 amps at 1300 watts rms a peice would i need another battery or could i run this off the 1 car battery the alternator will be switched out for a 120 amp 1 any help would be appriceated

[somefool]

for a true 3900w (power) then your alternator will kinda need to produce more than 300 amps.
(3900/13=300) 13 just to give u a bit of headroom

I have no idea about duel battery setups but you can sure get BULKY batteries which would suit the job.

Your doing this in a VN??!? Imagine the boot rattle!

[ti09ny]

lol sounddeadener will be my buddie i guess
so i need an alternator that makes more den 300 amps

[somefool]

woww. you should make a thread about this project up, I would be keen to see.

Yep, more than 300 amps. Ohms law dictates 300(amps)x14.4(volts)=4320

actually a 280 amp alternator would do the job nicely too. I wouldn't go lower than 270 amps because the most wattage that would make is 3888, so it would just keep up with the bulk power you want to run.

An easy way to work out for yourself: SUM the amp rating on the fuses of all your amps = reccomended amp rating of the alt.

Unless HCVP reads this and proves me wrong again :P

[ti09ny]

say i buy a 350 amp alternator would that be overkill

[somefool]

nah not really. 'Overkill' is in the eyes of the beholder. You also do have a car to run besides the amps. And it leaves you some headroom to upgrade in the future

[ti09ny]

ahh awesome any idea where i can get a 350 amp alt from

[somefool]

beats me lol. repco and the likes? auto electricians stock them. $$ though i reckon

[ti09ny]

prices doesnt really bother me......... much lol

[crazybiker]

A 350amp alternator is massive. When you consider that the stock one is around 80a or something similar. I'm not sure where you'd have to look, but it'd probably have to be a specialist shop, or see your local auto sparky. I highly doubt somewhere like repco would stock something like that.

[acarmody]

Do you plan on running a full 3900wrms all the time, that would be quite discomforting to be in the car, would also be really damn annoying to everyone around you.

If your talking comps though, another member here ran 5000wrms with the stock VS alternator and with a D31 battery, or was it two?

[SuperSixty6]

for a true 3900w (power) then your alternator will kinda need to produce more than 300 amps.
(3900/13=300) 13 just to give u a bit of headroom

I have no idea about duel battery setups but you can sure get BULKY batteries which would suit the job.

Your doing this in a VN??!? Imagine the boot rattle!

What experience do you have in CA?

That is possibly the funniest information i have seen for a while.

Audio is not constant, You will not need a 300amp ( L.O.L! ) Alternator unless you want major over kill.

[acarmody]

SuperSixty6 is right. How often will the sound system be drawing a full 3900wrms, a fifth of the time? Is this even for street use or for comp use?

[StoneX]

A fifth of the time? No.

Music is dynamic, it might draw that for milliseconds if all the amps were all playing the same frequency. Generally, the only time you will be drawing full power for an extended time (a few seconds) would be in an SPL comp where the amplifiers are playing a tone at full volume.

What is the system going to be used for? Just loud music?
When will the system mostly be played? While driving? While parked but with car running? While parked with car off?

The answers to those questions will help determine what you may need to upgrade in your electrical system.

[ti09ny]

its a street cruzer but i wouldnt mind entering it in comps every now nd then but mostly its just while driving on the street
yes its just so i can feel the music rattle my body lol

[ti09ny]

it will just be used as a street crusier nd comps every now nd den
nd mostly used will im driving

[SuperSixty6]

A fifth of the time? No.

Music is dynamic, it might draw that for milliseconds if all the amps were all playing the same frequency. Generally, the only time you will be drawing full power for an extended time (a few seconds) would be in an SPL comp where the amplifiers are playing a tone at full volume.

What is the system going to be used for? Just loud music?
When will the system mostly be played? While driving? While parked but with car running? While parked with car off?

The answers to those questions will help determine what you may need to upgrade in your electrical system.

Listen to this Man!

[StoneX]

Honestly, I would keep the stock alternator until it dies...

I put a system in my VT in 2001 which consisted of a 2400Wrms sub amp and 200Wrms x 2 speaker amp which is 2800Wrms total. Not as much as you but still much more than the car is made to sustain. Anyway, I stuck with the stock 100A alternator, upgraded the power and earth wiring in the engine bay to 0ga, bought a decent deep cycle battery (Optima Yellow Top) and had no problems until 2008. My alternator lasted 7 years before getting weak.

I think you should just ensure the wiring from you alternator to battery positive, battery ground to chassis and battery ground to engine block are all upgraded to 0ga. Your power wiring to the amps is 0ga. You have a decent battery to support the electrical system when the stereo draws more current than the alternator can provide.

If you're worried about voltage drop from the front of the car to the back, then you could put a second battery in the boot near the amplifiers but I'd see if you have any issues with the system before doing that.

[ti09ny]

ok thanks for that that makes alot more sense to me but 1 problem left i already put the power wire for the amp in and its 3 runs of 4 gauge should i scrap this for 1 run of 0 gauge wit a distabustion block for the amps or keep wat i got

[StoneX]

Three runs of 4ga can carry more current than one 0ga, so you're better off how it is.

But you might want to look at the site below and see if you think 4ga is enough for 1,300Wrms... I would only use 4ga for up to 1000Wrms or so.

WIRE

[ti09ny]

hmmm i havent bought the amps yet but that was bout the size i wanted i could go down couple of watts nd save some money at the same time

[ti09ny]

i was gonna run the 3x 1300 wat amps but so far it seems like overkill for a street car so
i wanna downgrade to help my hip pocket out too
the system i want is 2x 12" dual voice coil subs
2 sets of 6.5 splits in the fornt
nd just sum 6" in the back for the passingers
i still wanna have 3 amps
wat kind of power can i have on 4 gauge without pushing it
i plan on puttin in an optuma battery but is there any difference between the red nd yellow top
nd for all of dis would an alternator upgrade be requided

[ti09ny]

Three runs of 4ga can carry more current than one 0ga, so you're better off how it is.

But you might want to look at the site below and see if you think 4ga is enough for 1,300Wrms... I would only use 4ga for up to 1000Wrms or so.

WIRE

thanks for that mate acording to the site 1300 watts requires a larger gaue wire so im gonna drop the wattage abit just to be safe

[StoneX]

I'd just go for two 1000Wrms sub amps and a decent sized 4 channel to suit your 4 speakers... Or if you prefer better sound for yourself, a big 2 channel and GOOD front speakers and run some average rear speakers off the head unit.

Red top is a starting battery, high discharge current. Yellow Top is a deep cycle, which means it doesn't mind being flattened a bit and then recharged. Unlike regular batteries which become worn out quickly. That is my basic knowledge of them. I've always used Yellow or Blue for car audio applications. Blue is the same as the Yellow but has extra terminals which can be useful when attaching heaps of wires.

No, you won't NEED an alternator. With that much current draw you are going to get voltage drop which will be visible at night when your headlights and dash lights dim to the bass but there really isn't much you can do other than have an alternator that supplies 300A+ at all rev ranges which is not possible.

[somefool]

What experience do you have in CA?

That is possibly the funniest information i have seen for a while.

Audio is not constant, You will not need a 300amp ( L.O.L! ) Alternator unless you want major over kill.

Me I actually am just a keen amatur, so bugger all experience besides by own setup. I was under the impression that RMS was kind of an average output for an amp. So ya learn things everyday. its a forum, i tried to help the OP with the info that i had. Turns out it was wrong.

+ I wouldhave thought that even with the urgraded power, earths ect: with the power the OP wants to push, you would still get dimming on a stocko alt.

also as u guys know your stuff, You say the Full 3900wrms output. Does that mean RMS ratings are actually the most that the amp will output? (and 'max power' is an meaningless as the ex's love) Say my kicker 300zx birthsheet has 365wrms, thats is it's upper limit? Cheers