During the field tests on prototype 1, the maximum voltage value obtained in the internal capacitor was approximately 22V. The wind speed recorded that day was 22km/h, with gusts of 26-28km/h.

In the lab, if we spin the generator rotor until we get that 22V, we could measure the maximum RPM reached during the field tests. Other values of electrical magnitudes could be determined to try to characterize the nema 17 stepper motor in its role as generator in this Wind Turbine.
To carry out the experiments, a three-phase induction motor was used, which could vary the frequency of the supply current with a Variable Frecuency Drive (VFD) and with it, the RPM of its operation. This motor was attached to the chuck of a drill with which the generator shaft would be fixed. Attached to this mandrel was a small magnet that would pass close to a 2000-turn coil of fine gauge wire, when the entire assembly rotate. This coil would be connected to the signal input of an oscilloscope where pulses would be detected. Measuring the time elapsed between pulses with the same phase and determining its reciprocal, the frequency expressed in Hertz (Hz) would be determined. In turn, a multimeter would be placed at the generator output and the voltage and current would be measured based on the RPM. At the end graphs of dependency of these magnitudes based on the RPM would be generated. One area of interest was determining the best series-parallel configuration of 18650 lithium cells to be charged by the generator. Two 1500mAh 18650 cells balanced at a voltage of 3.7V were used in the experiments. Conclusions:
• The nema 17 stepper motor (generator) apparently is not capable of supplying a short-circuit current greater than 0.65 A. From 500 RPM, a pre-limit value of 0.6A is obtained.
• The 22V obtained during the field tests correspond to about 870 RPM of the generator. Typical values would be between 500-700 RPM.
• The open circuit voltage has a linear behavior as a function of RPM. At 600RPM approximately 14.5V is obtained.
• At typical 700 RPM  you get 0.5A charging current on a 1S2P 18650 system, versus approx 0.26A on a 2S1P 18650 system.
• It makes no sense to use configurations of three or more 18650 cells in series. High RPMs are required that this wind turbine could hardly reach.
This is all for now, tell me your opinion!