Using a 36-V Motor as a Generator

AC or DC motor?

If it's a 2W motor isn't there an impliction there that you will only get about 2W out of it as a generator?

To try it out, connect an electric drill to the shaft and measure the output. most electric drills can be run in either direction, so you can test both...
Del

DC motors make poor generators. The brush alignment to the magnetic flux is wrong (never forget it was designed as a motor!!)

How many Amps/milliamps at what voltage do you need?

If the motor was designed with an adjustable brush system (assuming a Brush/commutator system and not brushless), you may be able to readjust the brush position to allow generation at a reasonable level of efficiency, but many motors are simply designed with a fixed position. If you have a lathe, you may be able to do something to change that. The point of least sparking should give the highest output.

Car Alternators provide the easiest way to generate around 14.4 volts and keep a 12 volt LA Battery fully charged. This may not be attractive for any number of reasons for you of course.....but Car Alternators can be found with outputs from 25 to over 120 amps at any breakers yard, and therefore very cheap.

Truck Alternators can easily be found for around 29 volts, good enough to charge two 12 volt LA Batteries in series.......

By the way, I am told that Stepper motors with magnets (they "cog" when turned by hand), when turned provide a reasonable small AC output at low voltages, but I have never tried that myself....a few diodes will give you DC, a cap or two will get rid of the lumps!!

Basically we need more detailed and accurate infos before we can really help.

A. Schade,

You're not giving us a lot of information here for an informed answer. Presumably your designation of a 4 terminal motor implies that one pair of terminals are the stator field while the other pair is the rotor field. This configuration would require brushes to connect to the rotor windings. Brushes might imply a preferred direction of rotation as somebody else posted. If commutation occurs with the brush contacts, then you might have a DC motor. But this might be an AC synchronous motor with two stator terminals. One AC stator field circuit is intended to be some angle (90°) from the other. A capacitor in series with one field can provide the correct current lag. Possibly the other wires are a starter winding only that still requires the angle offset but expect a centripetal switch to open upon reaching a suitable RPM. Answering which configuration you have will help solve your question. If the wiring is either of the

If "2W" does mean two watts then you should not expect more than 55 milliamperes of current or 2 watts of power. But I would expect this to be a rather tiny motor then and would not give you the idea of generator use.

After you discover how to get the motor to spin, the no mechanical load, RPM rate should be the prime mover rotation rate to produce 36 volts (minus the core and friction inefficiencies). The number of poles in the motor will now determine the ratio between RPM and frequency out. This does assume that this is an AC synchronous motor.