Help!!!

[nutz358]

HELP!!! I have a Bosch alternator which I believe is from a B.M.W. I am using the alternator to make a generator. I need to know how to get voltage out of the alternator by just turning it. Max output from my alternator should be 14 v. From what I understand, I need to hook my alternator to a battery in order to induce it to start making a voltage. I need to know if this is correct. I believe I have sufficient R.P.M. through gear ratios, however, I am unsure the R.P.M. for optimum voltage output. Any input would be appreciated.
[/IMG]

[curtis73]

well, you can hook it up and spin it and measure output over a range of RPMs. You can also measure the crank pulley diameter, then the alternator pulley diameter. Divide the bigger by the smaller to get the pulley ratio and multiply vehicle RPMs by that ratio. The BMW probably had an inline 6 and their operating range is 500-6000 RPMs, and they cruise at about 2000. Multiply those RPMs by your ratio and that should give you a starting point.

You can't run an alternator without a battery. You can put a load on it, but the battery should be there to prevent spikes. Also, if you run an alternator without anything hooked up you can fry the alternator. The battery is always a wise idea

[nutz358]

Thank you so much for the input. If I hook the battery straight to the alternator, will it fry the alternator? Next question--- Will the alternator charge the battery or will the battery slowly die then need to be recharged?

[curtis73]

You would hook the alternator positive to battery positive and then a wire from the case of the alternator to the negative side of the battery. Alternators have regulated outputs, so as it approaches a set voltage (usually 14.4v) it reduces its output to maintain charge. Then as you draw juice out of the battery with whatever you're running, it supplies as much as is being taken out. And, since its hooked to a battery which completes the circuit, you won't fry the alternator even if there is no load being drawn.

For instance, if you hook up a 1200-watt appliance, its going to draw about 10 amps out of the system. The alternator's regulator senses this and starts supplying about 10 amps to the battery. In this way (just like in a car) the alternator only supplies what is needed to keep the battery full. If the battery is full, it supplies nothing (or at least very little). If the battery is dead, it will give its full effort until its charged.

Think of it like the water tank on your toilet. when you flush its like draining the battery. The float and valve are like the regulator in the alternator; they sense that its empty and open the water valve the whole way. It stays open until it starts reaching full, then it slowly closes the valve and stops when its full. If you compare that to your situation, you are slowly siphoning off some water out of the tank. The float falls just far enough to open the valve a little and it maintains the same rate of water in as you are taking out.

[nutz358]

thank you curtis I think that info will be extremely valuable.More questions will probably follow.