Does a bigger alternator increase horsepower?

>
>CCIT X Terminal ccx10wrote:
>
>>I just read the article in DB& Hot VW's about the new 75 amp alternator and I
>>was wondering if an auto electricican expert could tell me if it would draw
>>more horsepower from the engine. It is the same size, only with some special
>>modifications made by Kymco motorsports. Any input would be appreciated.
>

>The alternator rating is nothing more than the MAXIMUM current that
>the alternator can put out. If your old alternator doesn't put out
>enough then you will find that your battery slowly goes dead. Of
>course that may be because it is maxed out, or because there is
>something wrong with the alternator, the regulator, the wiring, or the
>battery, so it can be a bit difficult to decide.
>
>On the other hand, it is most likely that your present system puts out
>exactly what you need and the output of the HP system will be exactly
>the same: load limited.
>
>In either case, the power put out by your alternator must come from
>the engine. There is still no free lunch at the energy table.
>
>Jim
> ---------------------------------------------------------------------
> Melissa Kepner Jim Adney
> [email protected] [email protected]
> Laura Kepner-Adney
> Madison, Wisconsin
> ---------------------------------------------------------------------
>

Power Out = Power In - Loss
Efficiency = Power Out/Power In X 100

If you have a generator and an alternator, and (say) the alternator has twice the
output current rating of the generator then the power input to the alternator,
MUST, by the laws of physics, be MORE than the power supplied by the engines
rotation to the generator, UNLESS the efficiency of the alternator is TWICE that of
the generator, which I doubt.

I would think it a reasonable statement to say that a high output alternator WILL
take more power from the engine than a low output generator. Let's estimate HOW
much by an example.

If I remember correctly, I believe that 1 horsepower equals (roughly)
746 watts of electrical power. Assume an alternator is producing 13.6
volts and that (say) 55 amps is being drawn from it, by lots of
accessories and a nice sound system. Power = volts X current = 13.6 X
55 = 748 watts. Furthur, lets make the assumption (since we don't have
firm data from the alternator manufacturer), that the efficiency of the
alternator, in converting rotary energy to electrical energy, is 50%.
Then, if we are consuming 748 watts as in the calculations above, the
power taken from the engine is TWICE 748 watts, due to the 50%
efficiency figure we've assumed, and equals 1496 watts. Finally, if 1
horsepower = 746 watts, then the power taken from the engine is
1496/746 = 2.00 horsepower.

You do not get something for nothing. If you want LOTS of electrical
power, it has to come from the engine. If you're at a stop light, next
to a Porche, turn off your big stereo before you put the pedal to the
metal! :-}

JoAnne
'67 Bug Owner
M.S.E.E.

Most people are unfamiliar with high output alternators, but they can be very useful for producing the maximum charging power in a vehicle. They’re particularly good for motorsports where the demands on an alternator can be very high. Where more amperage is needed, a high output alternator can make for the ideal solution so the car isn’t continually undercharged.

No Dead Batteries

Where an alternator undercharges the car, it’s all too easy to end up with a dead battery. This will happen when a number of different devices pull ampage from the alternator or if the vehicle is operating in a particularly high-performance environment. It’s also liable to happen if accessories are left on while the engine is idling.

A high output alternator is built to cope with these demands and is designed to provide enough charge to power everything in your car without excessive effort. Many high output alternators deliver an output of up to 200 amps which will provide enough power without depleting the battery. Excessive output can lead to a dead battery when you try and start the car again.

Extreme Audio

Cars with large sound systems require high output alternators because large amplifiers and subwoofers use high levels of power. Every 100 watts of audio output requires 16 amps of power, so a heavy-duty system is going to make demands that are far beyond the capacity of a standard alternator.

A high output alternator which can produce between 140 and 225 amps is ideal for this. It’s possible to buy alternators with an even higher output with many starting at around 200 amps which go up as high as 300 amps. These will be able to take care of the most demanding accessories on an engine.

Off Road

Off road vehicles, especially those which carry a large number of lights, can benefit from high output alternators. The extra lights can draw more power than most standard alternators can handle. Similarly, a vehicle equipped with a snow plow will require a high output alternator since it produces a big drag on the electrical system.

Emergency Vehicles

Emergency vehicles, whether police or ambulance, require high quantities of power in the engine. They also have to run more items such as flashing lights and emergency medical systems. In previous times, these vehicles used regular alternators but they needed to be replaced quite regularly. A high output alternator can handle high electrical demands and doesn’t need to be replaced as often.

Hardwearing

Where alternator replacement becomes an issue, a high output alternator becomes a very economical answer. It may cost more initially but the subsequent longevity means that it pays for itself in other ways. It even saves a fair amount of money in the long run. High output alternators also tend to be more efficient than their regular counterparts and dissipate heat more evenly so the alternator doesn’t become too hot.

High output alternators employ heavy gauge wiring which ensures more of the current passes through to components. This contributes to the efficiency of the alternator as well as helping eliminate the possibility of undercharging.

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