Wind turbine low voltage at high speed , low charge rate to battery

danair Registered Users Posts: 2
I have recently tested a few wind turbines (SMARAAD -CHINA) rated 400 to 1.5kw in winds of 5 to 15 kts
the voltage on MPPT on the lower W units has been disappointing at around 6v dc at 10kts
the 1.5kw system maintains a 12V output at 10kts but has a poor charge rate on a 12V battery as the wind is not consistent

a bit disappointed with wind performance so far  - any advice 


  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    Raise the turbines 30-50 feet above the tree line.

    Advice, Small wind sucks. Use solar?

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former, 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Are these Vertical Axis Wind Turbines (VAWT) or Horizontal Axis Wind Turbines (HAWT)?

    VAWT-- I have never read of an installation where they supplied any useful power--And the few that turned--Some had blade flex and failed.

    HAWT--There is a critical mix of blade design, tracking the wind, and alaternator/generator design. The alternator/generator cannot have too much torque, or the blades stall. Too much RPM required for proper voltage/current, and too large of diameter, the tip speeds are too high and fail to generate enough torque. Wrong tail design and they fail to point into the wind reliably... Etc.

    And there is location and tower height. As Photowhit says, the tower has to be high enough for the wind turbine to "fly" in clean/non-turbulent air. 10-30+ meters tall tower (I think you are in Australia--Possibly in the Sidney area???). Upwind obstructions (buildings, trees, etc.) that cause turbulence just destroy the energy content of the wind--And no turbine (HAWT or VAWT) can harvest much wind. Tall towers can be expensive, take a lot of concrete (if self supporting), required a crane or other method to lift/service turbine, etc...

    At this point--It appears that a well designed and constructed Do It Yourself (DIY) wind turbine is probably better (more harvest, more reliable) than 95% of the other factory built turbines out there...

    And location--There has to be enough and consistent wind to harvest... Most turbines don't begin to supply "useful" amount of voltage/current at a minimum of 12 MPH (10.4 knots) and usually seem to max out at ~25-30 MPH (22-26 knots) before they automatically shutdown or otherwise limit their output/RPM.

    Harvest energy from wind goes with the cube of the velocity... 10 MPH^3=1,000 units; 30 MPH^3=27,000 units-- Or ~27x more energy at high wind... At low wind speeds, there is just not enough energy to be worth harvesting (let alone turbine aerodynamic and mechanical drag and electrical losses). And at high wind speeds, HAWT can easily self destruct (over RPM, blade failures, etc.)--And should have multiple methods to shut down (feathering, furling, electrical/hydraulic brakes, etc.). (VAWT generally cannot over-speed, but that does not make up for other VAWT design issues).

    This is an old link--But does show that even in a reasonably windy area with no obstructions, the turbines rarely performed as advertised...

    Small windpower a scam ? Survey says SO

    And one of the best performing HAWT of the day had lots of other issues that cause poor reliability over time:

    Truth About Skystream & SWWP

    More wind links here (old post from 2009--Some links are now dead or have a new home link):

    One of the more interesting (engineering wise, well written, lots of history) sites--And still active: (Wind specifically)

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • danair
    danair Registered Users Posts: 2
    good advice thanks for the prompt reply
  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    One quick trick to see if the air your turbine is in is turbulent or laminar (smooth)--Try flying a kite at that location. In clean air a kite will hold steady... In dirty air, it will not.

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