Using this tutorial as a guide, I have put together simple DIY wind turbine capable of giving around 2.5V - 3V output across the motor when spinning the fan blades. I can also light up some LEDs when connected directly across the output.

I have re-created this identical circuit, but did not include the schottkey diode: enter image description here

When connected via the DC booster, the USB output is a steady 5V. As soon as it is connected to a mobile phone, it shows a charging indication on the device and it stays that way as long as turbine is running. However, the phone battery does NOT charge. The phone goes into to "charging" mode (even with the device switched off), but fails to increase in battery percentage.

I have had the identical results with 3 different android devices and micro-usb cables. All seem to indicate charging has started, but the battery percentage does not go up at all, even if left running for hours. I also tried this with three different boosters: similar to one, two and three - all perform in the same manner.

The current shown on android apps varies wildly - most of the "battery charging / ampere" apps show a positive charging current of around 200mA ~ 500mA when the turbine is running. However one app (AccuBattery) always displays a negative charging current averaging around -200mA.

Any idea on what could be wrong with this setup or what can be done to improve things?

  • \$\begingroup\$ Please post a picture of your turbine. How big is the blade? What is the voltage on the boost converter output when connected to the phone? \$\endgroup\$ – Mattman944 Jul 31 at 19:57
  • \$\begingroup\$ @Mattman944 I don't have a photo on me right now, but we have a 12V DC "hobby" motor and the fan blades were taken from an old PC case / cooling fan. \$\endgroup\$ – Noddy Jul 31 at 20:02
  • \$\begingroup\$ @Mattman944 I did measure the output on the booster converter (without the phone connected) and it was steady 5V. I will measure the same once phone is connected and post back here. \$\endgroup\$ – Noddy Jul 31 at 20:03
  • \$\begingroup\$ your DC motor must run in reverse ;) to generate power +current and + voltage. That's one reason why a diode is used. THere are more reasons. but a 50mW LED lighting up does not meet you can start a DC-DC converter with higher start current. All your problems can be solved by specs for motor RPM vs wind speed and load regulation of speed from motor power output. Do you have any test results. MPT will be around 66% to 82% of no load RPM. YOur results indictate only a mismatch of impedance vs Motor Voltage/Current= impedance vs windspeed vs RPM, which all change \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jul 31 at 20:22
  • \$\begingroup\$ So you cannot use a simple DC-DC converter but need specs for a MPPT controller then a DC-DC controller or combined. 1st give specs or test results with a different V , I, R loads vs RPM vs wind speed at 82% no-load RPM. Can U do this using a current + voltmeter and tachometer for both motor and windspeed and active current sink using NPN power BJT (Darlington) load biased by a Pot.?? Not that hard to do. Ask if you cannot find a solution. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jul 31 at 20:29

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