joc45 replied:

Hi Rod,
The alternator can operate in either direction.
Optimum revs - These things start charging at about 700 engine rpm, and there is usually a step-up of 2 or 3 to one with the pulleys. But you will need more revs to get a good output, so I'd consider 2-3000 rpm on the alternator at least.

Provided there is a regulator, either built-in or external, you can then connect directly to the battery. Don't even think of it without a regulator. An unregulated alternator can deliver 50 volts or more. Most modern alternators have a built-in regulator, but sometimes there is an external sense lead; ie, volts are sensed at the battery and fed back to the alternator to operate the regulator. This is done to correct for voltage drop on the main charge lead.

Gerry

Wayne-o replied:

It does not matter which way you rotate an alternator, it is alternating current, and i don't see a problem with connecting it directly to a battery, although i am curious as to why you want to rotate one, in a direction other than that in which the engine is set up and why you want to connect it directly to a battery, as for optimum output, the revolutions of an alternator decide the frquency of the power output, ie 1500rpm=50hz, what you would get out of the wall socet at you house!

Mark Taylor replied:

You can rotate an alternator in either direction.. makes no difference to output.

However.. the caveat is that al alternator cools itself by drawing ain in the slip rings end, over the staor and rotor and out the other end.

Make sure your alternator has a unidirectional fan. Some don't.

Cheers

MT

kev.h replied:

Tried that with a small Honda generator ( parts were too dear so had the same thought as you) encountered the following problems
1- the motor probably will not drive the the alternator without mods as its is about 6 or 7 times the output which equates to 6 or 7 times the power to drive - the solution is to fit a variable resistance in the field circuit so you can adjust the output so you dont overload the motor i used a resistor from a variable speed fan
2- the coil was fed from seperate windings in the original generator- as the alternator does nothing under 500 + rpm no spark you have to wire in a 12 battery to get spark to start the motor
3- the points were driven from the end of the generator and not mounted on the motor so had to devise an electronic ignition system that could be driven from the alternator
4- it ran after much work but was too much trouble so i bought a $99 one from Home Hardware if it breaks i'll buy another
Realy cant understand why i spent so much time on the old one maybe i just like a challenge ( i have a shed full of failed good ideas)
Dont let me put you off at least you have some idea of what you are up against best of luck
Kev

Eric Experience. replied:

Rokkitt.
The fan is the only difference . if you can not find a left hand fan use one that has blades that run radially, Eric.