wind turbine mini recharge battery or not?

lindalufilindalufi Registered Users Posts: 1
Hi everyone.....

my teacher gave me project to make a small wind turbine to recharge battery (+- 9 volt), with speed of wind turbine is 200-600 rpm. and the power of motor is 0-20 volt.
but got a little bit confuse, is the wind turbine will product enough energy to recharge the battery or not?


  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    IMHO, answering the question should be a fail. There isn't enough info to answer (eg. battery chemistry, capacity, and state of charge, swept area of blades, wind speed, etc.). What grade is this teacher teaching?
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Super Moderators, Administrators Posts: 30,737 admin
    It is pretty difficult to design a "working"/"useful" wind turbine with the right components. With an unknown set of items, it is that much more difficult.

    For the "generator"... There are two major types. One is a DC brushed motor/generator that supplies DC voltage/current. Another is an Alternator that generates AC voltage/current.

    Assuming you have a DC brush motor (basically connect a voltage source like your 9 volt battery) to the leads and if the motor turns, then it is a DC Brushed (universal) Motor that can be (in theory) connected directly to the battery to recharge (you would need a diode to "block" backward flowing current (your wind turbine/generator becomes an electric fan).

    Somebody has told you that you need to spin the motor at ~200 to 600 RPM for the motor to generate more than 9 VDC output (needed to charge the battery).

    There are different "blade" designs. There are low speed types (lots of blades, not too aerodynamic) and there are highspeed designs (look more like an airplane propeller (just a few blades).

    If you have a low speed blade design (typically easier to make), then you may need a pulley system to take the low RPM spinning blades into a the high(er) RPM required for the generator.

    And there is also the amount of effort needed to spin the generator... Low voltage and low current, not too much torque is required (small/simple blade design). A larger generator (higher voltage and/or higher current), you would need a larger blade set to generate more torque (turning effort).

    And there are limits to how fast a typical turbine can spin based on the "tip speed" of the blades (very large turbine blade set turns at pretty low RPM. Small (short) blade set can spin very fast but not much torque).

    There is a pretty famous boy (now adult) that designed and built his own wind turbines from scrap bicycles and other parts. Search for:

    Malwai boy built wind turbines for village
    William Kamkwamba

    You can see some of his designs if you look around. They have relatively low output energy (12-20 Watts it seems). And these are relatively tall towers with significantly sized "fan disks". Relatively inefficient--But they did work for his needs.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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