how big alternator?

[audio-freak123]

i plan on getting a 3000rms amp, how big of an alt. should i get?

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[Bob Saget]

this big

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[MONSONwarrior Premium Member]

I'd go as big as possible, 275 maybe 300 amps.

 

[keep_hope_alive Premium Member]

totally depends on the actual amp (make/model) and the load (ohms). what amp and what load?

 

[maddog 10+ year member]

I second the big as possible answer.

 

[Stryker 10+ year member]

X3 on the big alt.

not cheap but worth it.

 

[Hellbound Train 10+ year member]

Depends on current draw of your amplifier.

 

[DonWan 10+ year member]

To calculate the current draw of an amplifier, multiply the number of channels by the RMS watts per channel (a 2 channel amp rated at 300 watts RMS per channel would be 600 watts). Double it to account for amplifier inefficiency (600 watts X 2 = 1200 watts), then divide by the average output Voltage of an alternator, 13.8 volts (1200 divided by 13.8 = 87 amps). Since the average music signal requires about 1/3rd of the average power in a test tone, divide by 3 (87 amps divided by 3 = 29 amps). The result is the amplifier's approximate average current draw.

 

[keep_hope_alive Premium Member]

^ you neglect a few key components.

1. you need to factor in the impedance load on the amp. A 4 ohm load uses less current than a 2 ohm load for unregulated amps. If you have a JL slash or Alpine PDX or similar, then impedance isn't a factor. Impedance load determines output power capability.

2. amplifier efficiency depends on the Class. Class A/B is typically 50-60% at best, depending on the impedance load. Class D can reach 85% efficiency, again depending on the amplifier topology and load. I always take the amp class into consideration.

3. always consider the quality of the amp. A Boss audio amp won't make rated power. A Rockford Fosgate will. The latter is much more expensive for the same printed "wattage".

Average signal music being 1/3rd is a gross approximation, while quite accurate, doesn't help when sizing an alternator. If you want to prevent voltage dips, meaning you need to consider peak levels, or at least 2/3rd levels.

You need to consider what output you need at idle. more output at idle means a higher max output, and a larger load on the engine. a 4cyl engine's performance and fuel mileage will suffer when a HO alt is added. a V6 or V8 will just suffer fuel mileage. Good alt manufacturers will offer an output curve for their alt, showing output at various RPM.

When upgrading the alt you are upgrading all of the wiring associated with the alt. the new wiring needs to be properly sized, fused, and routed. Take your time on this so you don't have a rolling fire hazard.

Some cars use load detection (i.e. Honda ELD) to turn off the alt to safe fuel mileage. If this is the case, an HO Alt alone won't do much for you. You need to bypass or control the load detection to force the alt on in high current usage.

Finally, a battery bank needs to be considered if you plan on competing in SPL or turning the car off and leaving the tunes play. Battery banks are expensive and require skill to implement safely. They can be deadly if not done correctly.

 

[Cabin_Pressure 10+ year member]

A true 3KW will need a reserve batt bank also. As stated above.

 

[9515ROB 10+ year member]

i had a 200amp charging 4 batts and it kept up very well with my dd z2 and everyone knows thats a current hog and i didnt drop below 13v

 

[bubbagumper6 5,000+ posts]

To calculate the current draw of an amplifier, multiply the number of channels by the RMS watts per channel (a 2 channel amp rated at 300 watts RMS per channel would be 600 watts). Double it to account for amplifier inefficiency (600 watts X 2 = 1200 watts), then divide by the average output Voltage of an alternator, 13.8 volts (1200 divided by 13.8 = 87 amps). Since the average music signal requires about 1/3rd of the average power in a test tone, divide by 3 (87 amps divided by 3 = 29 amps). The result is the amplifier's approximate average current draw.

*facepalm*

 

[audio-freak123]

totally depends on the actual amp (make/model) and the load (ohms). what amp and what load?[/QU
its a massive 3000.1 its cea rated so ik it puts out rated power or close to it but i just wanna no if theres a way that i can get close to 3000rms buy only getting a big alt like 200 amp, and upgrade all factory wires to 0/1 guage and possibly a capacitor?

 

[MONSONwarrior Premium Member]

totally depends on the actual amp (make/model) and the load (ohms). what amp and what load?[/QU
its a massive 3000.1 its cea rated so ik it puts out rated power or close to it but i just wanna no if theres a way that i can get close to 3000rms buy only getting a big alt like 200 amp, and upgrade all factory wires to 0/1 guage and possibly a capacitor?

all the CEA rating does is jack the price of the amp, Kenwood makes an amp CEA rated at 900 watts when it only puts out 600. You'll probably need 250a, l0 gauge (maybe two runs), and then at least one battery in the back.

 

[Cabin_Pressure 10+ year member]

totally depends on the actual amp (make/model) and the load (ohms). what amp and what load?[/QU
its a massive 3000.1 its cea rated so ik it puts out rated power or close to it but i just wanna no if theres a way that i can get close to 3000rms buy only getting a big alt like 200 amp, and upgrade all factory wires to 0/1 guage and possibly a capacitor?

If it actually does 3k, then no.