Battery charger

[MikeHump]

Originally Posted by B-Rex

Did I hear someone call for Mr. Science?

Basically, the difference between an alternator and a generator are the "types" of electricity they produce internally. Without getting too nerdy:

What we call a "generator" is generally thought of as producing "DC" or direct current....meaning that it produces power steadily with a constant polarity (i.e., positive and negative).

An alternator produces alternating current (AC)...meaning that a particular output alternates between positive and negative (this is an ovesimplification as I'm leaving out the phases....but it's easier to explain this way).

The bottom line is this general axiom:

An alternator is usually lighter, stronger and more efficient than a generator. It uses solid-state diodes (electronic one-way valves) to eventually produce a DC current to charge batteries and run the electrical system.

A generator uses a mechanical "commutator" to output DC and is therefore. heavier, less durable and more complex.

The truth of the matter is that the electro-magnetic portion of both the alternator and generator is essentially the same...the difference lies in the commutator and the built-in diodes.....both in the end produce DC current for motorcycle/automotive electrical systems.

B-Rex

You would be correct!

I don't know why motorcycles use generators. I guess in principle though, an AC generator is the same thing as an alternator, but it would make more sense to use an alternator similar to what's in a car, for weight reasons. The output is also usually a lot higher with less draw from the engine on an automotive-style alternator.

[B-Rex]

Originally Posted by MikeHump

You would be correct!

I don't know why motorcycles use generators. I guess in principle though, an AC generator is the same thing as an alternator, but it would make more sense to use an alternator similar to what's in a car, for weight reasons. The output is also usually a lot higher with less draw from the engine on an automotive-style alternator.

I totally agree, which makes me wonder if modern bikes really do use an alternator and they just call it a generator because of tradition. Interesting question...I'd like to know if anyone knows.

It really would make more sense if it was an alternator as you pointed out, Mike.

B-Rex

[Jay313]

Feeling smarter already

[MikeHump]

Originally Posted by B-Rex

I totally agree, which makes me wonder if modern bikes really do use an alternator and they just call it a generator because of tradition. Interesting question...I'd like to know if anyone knows.

That actually might be the reason, just for tradition's sake.
I would like to know as well, though!

With all of the new EPA regulations on bikes, the EVAP systems and catalytic converters take enough power away from the engines, it would only make sense to use an automotive style alternator for maximum power and efficiency.

[B-Rex]

Originally Posted by Jay313

Feeling smarter already

Jay, there are many really experienced and knowledgeable people here regarding every aspect of motorcycling. I wish I knew all that they know. You hang around and you will be amazed how much you learn. Between the wisecracks and the anecdotes are an incredible amount of experience and wisdom. And, it's all free!!!

I wish I had had this forum available when I first got into bikes. It would have saved me quite a bit of skin, bruising, trial and error and MONEY!

Welcome aboard.

B-Rex

[Barbarian]

So, am I the only one who lets his battery sit over the winter, then checks the voltage every 3 weeks with a multimeter to see if I need to charge it?

[omegajim]

All bikes now and for quite some time use "alternators."

Pretty much for the same reason cars back in the 60's went to alternators.

1) lighter
2) can generate more power.

The old generators in cars could produce something like 400 - 500 watts of power.

You start putting all sorts of gizmos on a car and that's not enough.

A modern car will typically have an alternator (with bridge diode built into the unit ) capable of 80 amps at 14 volts. That's 1120 watts of power, more than enough for a lot of things.

A bike will have an alternator (although the bridge unit that converts ac to dc is external) for weight considerations. The diode bridge is external for heat dissipation.

How far does this go back?

I can personally vouch to at least 1980, as my Honda had an alternator on it.

But out of a matter of tradition, they still call them generators on bikes.

[B-Rex]

Thanks omegajim! You help answer an interesting question. Now the motorcycle-generator connundrum makes sense.

B-Rex

[Rickster]

The other thing about generators, besides not being able to produce as much power as the same size/weight alternator, they will at low speeds (idle) produce no power at all, in fact they will draw power off a battery. An alternator doesn't have to be spun up to produce power, and as an added bonus, there are no brushes to wear out & dirty things up.