I was in Futureshop the other day and I saw all these aftermarket amplifiers for cars and it got me thinking; how much electricity does an alternator actually produce?

Some of these things are marketed as 600 watts, which seems quite high. Granted, these are most likely just peak loads and not continuous, but at 12V, 600 Watts means the alternator has to push

P = V*I
I = P/V
I = 600W/12V = 50 Amps

That's alot of current. I can't see how the alternator produces that much current and how the wiring in the car can handle that much.

Consider the 2k2-2k3 Maxes. Its a cold winter day, so your running the heating elements in both front seats, the heated steering wheel, and the rear defroster. You've got you're hid's on with your fogs, the wipers are going, and you've got the Bose blaring. That has to add up to alot of juice.

I know that the car companies are considering going to a higher voltage (24 or 36 V) so they can drop the current and still meet the demand of the electronics in the car. Just curious...

 

When an aftermarket amp says it's pushing 600w it doesnt' mean it's also eating that much power.

Btw, i think the Max has an 11 amp alternator. Not exactly sure but it should be in that range.

 

I think it is a 120 amp unit.

 

whoops, forgot the 0

 

110 - 120 watts is right for the car alternator. Actual power consumption of an audio amp will be a little more than the RMS rating (probably much less than 600w) at full volume and continuous tone. This is an unusual condition. Music is usually not really continuous, but many bursts, this is why stiffening caps work - they provide extra power for the short term loads rather than the average.

 

Do you amps or watts?

Aren't the high beam bults 55W each? Doesn't seem to add up.

As for the amplifier, I figured they had alot of capacitance to hit those peaks if the car electrical system can't provide. Makes sense too, since music is so dynamic. You're average power consumption is fairly low, and the the caps kick in to provide you with the extra juice when needed.

 

Yes, 120A (amperes) not W (watts)

Capacitors: They store charge per time Q = CV (coulomb = farad * volts). A capacitor can provide proper dampening as long as the charge per time stored is greater than the charge per time drawn by your amlifier.

Most audio shops recommend huge caps just from a overkill perspective but they are usually overpriced inferior grade caps. (lack high ESR, long life dielectric and uniform plates and distance).

As for RMS power rating: Amplifier makers use a 1 Khz sine wave to drive the amplifier and measure the maximum undistorted peak to peak voltage it can produce into a load (better audio makers make sure the load repesents closely the characteristics of a real world speaker, inductive load). This peak to peak value is then multiplied by 0.707 and that gives you the RMS power rating. eg 100 v (p-p) = 70.7 v rms.

hope that helps
woosh

 

Sorry - 120amps, 1440watts. Yes, the big amp numbers advertised are not usually RMS but IPP (peak) or similar ratings. A really good amp wouldn't benefit from a stiffening cap because it would have it's own.