12v DC wind turbine - and connecting straight to 2 large 12v batteries.

GonzoTheFreakGonzoTheFreak Posts: 1Registered Users
Hi, new here, quick question for all you guys in the know: I've got a 200watt solar power generator set up, can I simply connect the 12v DC wind generator to the batteries or must I buy a hybrid controller... Or even just double up the wires going into the charge controller for the solar? I'm new to this, got until the end of the month to sort it all out before I set up for full-time use. Thanks for any help in advance!


  • BB.BB. Posts: 27,882Super Moderators, Administrators admin
    It depends on your wind turbine... Some have internal battery charge controllers. Others need an external controller.

    The "typical" setup is Wind Turbine -> rectifier -> battery bank -> Diversion Controller -> resistance heater

    The idea being that most wind turbines will over speed in high winds if they are not loaded (connected to a working battery bank). When the battery bank is full, a diversion controller "turns on" and dumps current to an electrical heating element. When the battery is less than 100% full, then diversion controller turns off and the battery is charged again.

    And you would keep your solar panels+charge controller connected as it was (directly to the battery bank). The solar charge controller will turn the panels on/off as needed to keep the battery bank charged (assuming you have enough sun+solar panels).

    Wind turbines are not usually the easiest/best way to help charge your battery bank (a tower to hold the turbine, and the wiring+charge controllers for wind turbines are not cheap--plus most people do not have enough wind on site).

    But since you already have solar panels (and perhaps you may want to add more)--Experimenting with a wind turbine as an additional power source may be helpful for you.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • paulgilpinpaulgilpin Posts: 1Registered Users
    i want to horn in on this conversation, and hopefully bill will answer, as his reply was so measured.
    first this is a bonehead question/statement.
    if you have eight(8) six volt batteries in series for a 48v system, and let's say you want to buy a small wind turbine just for giggles ( yes i know, that's an expensive giggle ) and you buy a 12v wind turbine.  what happens if you connect the leads of the wind turbine across two of the six volt batteries?  a 12v potential difference.
    the reason i ask is because i have heard with some systems, in order to charge a 48v system the turbine has to be in gale force winds to start charging.  but if it's just a rectifier, it will start putting out 12v at slower wind speeds.
    either that, or i don't know how an alternator works.
  • BB.BB. Posts: 27,882Super Moderators, Administrators admin
    OK... Lots of questions there.

    If you put a charging source across the 12 volt segment of a 48 volt battery bank--You will simply charge just that segment of cells (assuming that both the + and - charging source leads are floating, and NOT ground referenced).

    Charging just a 12 volt segment of a 48 volt battery bank does not help much of anything... The rest of the 36 volts worth of cells have not been recharged.

    You do have options... You can charge a 12 volt bank and use a 12 volt to 48 volt converter to charge the whole 48 volt bank (you may be able to find a 12 VDC to 48 VDC converter and directly connect, and bypass the 12 volt battery bank).

    There is another "interesting" method of charging/discharging a "split battery bank". Used in heavy duty vehicles/RV conversions (bus/truck conversions)--24 VDC vehicle chassis and a 12 volt "house power" (RV inverter, solar/wind charger/etc.).

    You connect a 12 volt to 12 volt isolated DC converter across the A and B battery segments. The DC converter keeps "equal voltage" across the two halves of the 24 volt battery bank. This allows any combination of 12 and 24 volt loads/charging sources to use the bank "optimally" while the isolated DC to DC converter tries to keep the voltage of Bank "A" equal to the Bank "B" voltage. The DC converter can move energy in either direction.

    You do not want to "unbalance" a string of cells/batteries (tap 12 volts from a 24 or 48 volt battery bank). Very difficult to get the batteries back in balance... And the battery bank is only as good as the "weakest" cell/battery.

    The output voltage of an alternator is, more or less, proportional to RPM. Spin the alternator 2x faster, the open circuit output voltage doubles too.

    Current output is also proportional to RPM (faster RPM, higher output current). A 12 volt alternator can output 60 to 100+ volts if the RPM is high enough.

    Of course, you need the alternator to overcome rectifier/wiring resistance. So, while the alternator may generate (random example) 40 volts open circuit at 400 RPM, it will only output 45 Amps @ 12 volts at 400 RPM.

    http://www.windynation.com/jzv/inf/open-circuit-voltage-and-short-circuit-current (nice chart 1/2 way down page)

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • willsiowillsio Posts: 3Registered Users

    If your wind turbine already has a 12v DC output, is it possible to connect it directly to a 12v battery bank (considering that the battery bank is already connected to a solar charger controller)?

    Something like this:

    Wind turbine (12v) <---> Battery Bank (12v) <---> Charger Controller (12v)
    Solar Panels <---> Charger Controller (12v) 

    Thank you
  • BB.BB. Posts: 27,882Super Moderators, Administrators admin
    Assuming this is a horizontal axis wind turbine with a rectified (DC) output voltage connected to the battery bank, you would need a "dump" controller connected to the battery bank and a resistor (heater) bank to absorb the excess charging current from the wind turbine (battery full, need to dump power somewhere to prevent the turbine from overspeeding).

    And, yes this can be done in parallel with the solar charge controller.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • willsiowillsio Posts: 3Registered Users
    Thank you very much Bill :)
  • BB.BB. Posts: 27,882Super Moderators, Administrators admin

    As always, the devil is in the details. If you have more questions, I suggest you open your own discussion and we can help you there (easier to keep all questions and answers related to your needs).

    There are lots of rules of thumbs that we use to "size" and design a reliable/cost effective system. It is possible, if you do some of these wrong, to create a fire/safety hazard with your system (wind systems can be very difficult to make safe and reliable--Many times, adding more solar panels and/or a backup genset is a better solution).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • willsiowillsio Posts: 3Registered Users
    OK Bill, at this moment I have a small wind turbine and a solar panel, both working with grid tie inverters, so now I would like to know more about off-grid systems and probably I'll open some new threads.

    This forum seems to be a great place for sharing thoughts and learning good practices. 
    Thanks for your advices :)
    PS: By the way, sorry if my English isn't perfect, English is not my native language.

  • BB.BB. Posts: 27,882Super Moderators, Administrators admin
    No worries... English (or at least "American") is my native and only language--No good excuses why mine is so poor. :'(

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • akarshshastryakarshshastry Posts: 1Registered Users
    hi everyone can i connect a wind turbine directly to an inverter (wind turbine -12 v dc dc converter- inverter-cfl)?
  • BB.BB. Posts: 27,882Super Moderators, Administrators admin
    While it is technically possible to design such an off grid AC inverter--I do not know of any (perhaps somebody can let us know of any such inverters).

    There are Grid Tied inverters that can take output from wind turbines and connect them to the utility grid (or even "micro grid" installations that use a TSW off grid AC inverter).

    You want to run CFL lighting from the wind turbine? That seems to be something that is not going to be very successful. A wind turbine has highly variable output and the bulbs will flicker/dim/brighten/etc. depending on wind/gusts/becalmed conditions.

    If you want to discuss your needs/ideas in further detail, please feel free to start your own thread. It is usually easier to keep all of your questions and answers in "your thread".

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jonrjonr Posts: 1,073Solar Expert ✭✭✭✭
    I suspect you would be much better off using 12V LEDs.
  • censorcensor Posts: 1Registered Users, Users Awaiting Email Confirmation
    Please i'v got a problem folks. I got a 48-53Volts DCDU power source. Can i connect a 24Volts DC-AC Inverter to it? Please am on site, in need your help
  • BB.BB. Posts: 27,882Super Moderators, Administrators admin
    No, not easily... 24 Volt AC inverter needs ~21 to 30 volts DC to work correctly.

    You would need to "down convert" from 48 volts to ~27 volts via DC to DC converter or even use a MPPT type solar charge controller and a "local" 24 volt battery bank.

    Obviously, the best solution is usually to by a 48 VDC volt input AC inverter.

    Details matter... If you have more questions, please create your own "discussion" (thread) on the forum. We can talk about your needs there.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • GilbertGilbert Posts: 4Registered Users
    Plan to install hybrid wind/solar system on my roof. I knew from other discussions that installing horizontal axis turbine is not effecient due to turbelence caused by some obstructions, otherwise it will be installed high enough where a good quality or less turbulence of wind is experienced. What about installing vertical axis? I know that this cater or receive wind from all directions, do you think this is good to install? Plan only around 600 - 800 watts. Thank you.
  • BB.BB. Posts: 27,882Super Moderators, Administrators admin
    Several issues with your potential installation.

    First, wind turbines place a lot of stress on the building and transmit noise into the structure. For a wind turbine of any size, highly recommend that you do not mount to your home.

    Second, there just is not much energy in turbulent air at all. Horizontal Axis Wind Turbines certainly cannot track/change direction very quickly, but Vertical Axis Wind Turbines cannot pull energy out of turbulent air either.

    You can read about a large company that exited VAWT field last year after many issues:


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