Alternator Size?

[eltortuga94]

How do you calculate what size alternator you should be using?

What size alternator should be used when running 3600 w/rms?

Edited September 7, 2011 by eltortuga94

[eltortuga94]

Bump

[BJD3]

Easiest way of doing it is adding the total of the amplifier's fusing to the rating of your stock alt.

You'll have overhead, but overhead isn't a bad thing.

[Socky]

If it was me, i would put the biggest alt on the vehicle so i have room for upgrades.

[eltortuga94]

ok. what about dual alternators setups? like say two 200 amp alts, would that be 400 amps?

[The Teen Audiophile]

ok. what about dual alternators setups? like say two 200 amp alts, would that be 400 amps?

Well 400 Amps on 12.6 volts is 5040 watts, and at 14.4 it's 5760 watts. But mind you, 200 amp alternators rest at about 130 amps at idle and about 155 at 3000 RPM, and 200 amps at 8000RPM

[eltortuga94]

ok. what about dual alternators setups? like say two 200 amp alts, would that be 400 amps?

Well 400 Amps on 12.6 volts is 5040 watts, and at 14.4 it's 5760 watts. But mind you, 200 amp alternators rest at about 130 amps at idle and about 155 at 3000 RPM, and 200 amps at 8000RPM

Thanks. I was only using a 200 amp as an example.

[HHR Ed]

Actually, 200A alts do not make full power at 8000rpm.

It depends on the alt and each has its own rating through the rpm band.

Some alts make full power at 2000 rpm.

Best way to figure what you need electrical wise is this.

First figure what wattage you want to run, how many of what size amplifiers.

Lets use a 10,000w amp as an example.

OK, so first I wanna choose the batteries to power that 10,000w amp.

I want a bit of overhead and have to figure voltage drop as well. Most amps will shut off at 10v so if we use that as a reference, it'll give us overhead automatically.

Also, most amps are 65-90% efficient, so we need to figure on making more that 10,000w. Lets choose batteries that can deliver about 15,000w at 10v.

So our batteries must be capable of supplying 1500A of current.

About 3 XS Power D3100s can handle that. Why not 4 for a bit of reserve, shall we? Because we have the 4channel amps and the engine too.

So no we have 4) XS D3100s to charge while playing. They have a total aH rating of 440. So with a draw of 1500A, the batteries alone will die in about 20 minutes or so, playing full tilt.

if we use a 200A alternator, we can extend that to about 25 minutes. A 300A would extend it to about half an hour.

So now figure your playing habits. Are you playing tones at 100% power for 30 minutes straight? Probably not.

How bout playing music at 75% power on average for 30 minutes? Sure. Well transients dont pull full power at all times, so with this, the 30 minute playing time can be extended for hours.

And everytime you pause or mute, or there is a break in songs, the alts will be charging the batts. With about 75A of charging to each battery. That is pretty good. Going larger will increase performance. But that'll do well in a situation like this. The smaller the alt, the longer it will take to charge up the batts and let playing time you will have. Going larger will increase playing time and speed up recharge.

75A of charge can recharge a fully depleted D3100 in just a couple hours. When playing with music and once in a while go to 100% power for a few minutes, you may only deplete the batteries a few percent. So recharge to full will only be a few minutes.

Basically what Im saying is to get the largest Alt you can afford.

[Pittcrew]

Actually, 200A alts do not make full power at 8000rpm.

It depends on the alt and each has its own rating through the rpm band.

Some alts make full power at 2000 rpm.

Best way to figure what you need electrical wise is this.

First figure what wattage you want to run, how many of what size amplifiers.

Lets use a 10,000w amp as an example.

OK, so first I wanna choose the batteries to power that 10,000w amp.

I want a bit of overhead and have to figure voltage drop as well. Most amps will shut off at 10v so if we use that as a reference, it'll give us overhead automatically.

Also, most amps are 65-90% efficient, so we need to figure on making more that 10,000w. Lets choose batteries that can deliver about 15,000w at 10v.

So our batteries must be capable of supplying 1500A of current.

About 3 XS Power D3100s can handle that. Why not 4 for a bit of reserve, shall we? Because we have the 4channel amps and the engine too.

So no we have 4) XS D3100s to charge while playing. They have a total aH rating of 440. So with a draw of 1500A, the batteries alone will die in about 20 minutes or so, playing full tilt.

if we use a 200A alternator, we can extend that to about 25 minutes. A 300A would extend it to about half an hour.

So now figure your playing habits. Are you playing tones at 100% power for 30 minutes straight? Probably not.

How bout playing music at 75% power on average for 30 minutes? Sure. Well transients dont pull full power at all times, so with this, the 30 minute playing time can be extended for hours.

And everytime you pause or mute, or there is a break in songs, the alts will be charging the batts. With about 75A of charging to each battery. That is pretty good. Going larger will increase performance. But that'll do well in a situation like this. The smaller the alt, the longer it will take to charge up the batts and let playing time you will have. Going larger will increase playing time and speed up recharge.

75A of charge can recharge a fully depleted D3100 in just a couple hours. When playing with music and once in a while go to 100% power for a few minutes, you may only deplete the batteries a few percent. So recharge to full will only be a few minutes.

Basically what Im saying is to get the largest Alt you can afford.

Very good info, cause I've been actually wondering the same thing, thank you!