Feeling stupid need help! LOL

[tnhomestead]

Made a 12 volt DC gen from an alternator and a small motor -- 60 amp alternator, 6.5 horse motor, 5 inch pulley on motor, stock on alternator, BUT when I start it up and then hit the switch for the alternator, the gas motor acts like its bogged down and dies -- any ideas what I am doing wrong? Want it to supplement my solar system! Thnx in advance fer any ideas!

greg

[Flux]

If you are using the internal regulator (or no regulator and full field) the thing will take more than 6.5hp.

Try adding some resistance or some 12v lamps in the field circuit to limit the maximum current.

If you don't follow what I am on about there are hundreds of articles on the net about controlling car alternators for standby battery charging. There will be plenty of information if you search this board, I am no good at finding such things.

Flux

[wpowokal]

Greg as Flux said and........

I have run a 55A 24v alternator off a 5.5hp motor with a 4" pully on motor.

In your case I would go for a 4" pully on the motor, that 1" in diamiter will make an enormous difference, even at a 1:1 pully ratio the 3000rpm motor will still run the alternator to full power.

Don't be fooled into thinking you can run the motor at a low rpm to save gas even if it can supply the HP it will get hot.

allan down under

[wooferhound]

What are you going to use the power from the Alternator for ?

[suitep123]

Flux

its real early, But couldn't he run a reostat maby even an older car or truck headlight dimmer switch to feed the field windings? I dont think they get full battery voltage?. Rembering isn't my strong point. maby check the voltage being ran into one when a car is running and charging

Bob

[Flux]

Yes that is the idea. Rheostats may not be easy to find but wire wound resistors or car lamps will do the job.

The faster you run the alternator the less field it needs for a given output.

Allan is also right in that a smaller engine pulley would get the same result by letting the engine speed come up and let the engine come on to its proper power curve.

These alternators will work up to about 12000 rpm but need little field at that speed and the torque doesn't match the engine.

The ideal speed is that which will just give full output with full field on a reasonably charged battery, it will give easiest load to the engine and require only a small drop in field volts. If you get the speed right it will even work with the internal regulator but becomes rather inefficient as the battery comes near to full charge as the alternator will hold it at normal float volts and when you are trying to recover after low wind or sun you need to get up to the bulk charge current.

Probably there is no point in running the alternator over 3000 rpm.

Flux

[suitep123]

I have seen many automotive dimmers that I havn't gotten the chance to check but thought they would make great 12volt Rheostats. Dont know positive yet.

I do beleve a Briggs motor is cammed for max power to give a generator rpm derect drive somthing like 4250 rpm. I could check with a cart racer to be sure and should anyway.

Early to work to bead blast some 10 foot mill steel.

Bob

[suitep123]

Hello again:

    This morning I said "I do beleve a Briggs motor is cammed for max power to give a generator rpm derect drive somthing like 4250 rpm" - in actuality, the Honda generators are cammed to run at 3750 rpm, and if memory serves, which it did not this morning, the Briggs motor is about the same.

    Just thought I quickly throw that in and correct myself.  Y'all have a great day!

              Bob

[smidy]

I made one gasalternator for a few years ago, it was made with a B&S 3,5 hp gasoline engine and a bosch 35A alternator. the engine and the alternator was bolted in to a steel frame, at once i engaded (power to fieldcoils) the alternator the engine died, it was not lack of power, it was someting strange with the ignition system on the B&S that did not could stand the alternator when it was charging, the solution was to insolate the engine frome the steelframe, dont ask why, it was fine for me when it was charging :-)  

[tnhomestead]

Thanks for the ideas -- back from the Dentist so will try the rheostat in the am. Why do all dentists go to the Marquis De Sade School of Dentistry and Sadism? LOL

The charger is just for secondary battery charging if needed and the semi isnt here(has a nice new aux motor) Appreciate the help, now onto the roof and some aolar panel work!

[suitep123]

Greg

Tell us what worked and all,

Maby a picture and description when you get it dialed in.

Bob