Newbie charge controller question

silent57 Registered Users Posts: 2
Hi everyone. I'm very new to the wind and solar power scene. I haven't bought anything yet, just trying to learn first. I have a question about charge controllers. Excluding MPPT controllers, do typical charge controllers (say from missouri wind and power) regulate the incoming voltage from the wind turbine? For example, lets say I have a turbine generator that used to be an old treadmill motor. Now lets say that this motor typically puts out 40 volts. Will a normal charge controller that's not MPPT take that 40 volts and make it suitable to charge a 12 volt battery bank? Remember, this is just a hypothetical situation. If it's too much voltage for a 12v system, I would also think that it is too much for a 24v system, but not enough for a 48v system.

A slightly different but similar question is, can a professionally made 48v PMA charge a 12v battery bank as well as 48v? Or can it only charge 48v banks? I appreciate any help on how a typical non MPPT charge controller works. I have done some research on my own, but all the information I find makes it sound like the charge controller only regulates the charge on the battery and not the incoming charge from the wind turbine. If I got a hold of an old treadmill motor and it creates 40v I just don't want to be putting 40v directly into a 12v battery bank. I don't think that's okay anyways.


  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Newbie charge controller question

    Welcome to the forum.

    The answer is "yes, but no". :p

    Typically a wind turbine controller does not interrupt power to the batteries thus regulating the Voltage. Instead the full output is put to the batteries, causing the Voltage to become a current and force the battery Voltage up. When it reaches a set level, the controller then connects to dump load which "drains off" the excess power keeping the Voltage at the correct level. This is known as "diversion control". You can see a basic diagram of this type of use on Page 2 of this data sheet from Morningstar:

    As such, having the Voltage potential of the turbine too far above the system Voltage can cause trouble in the form of too much current. Hence the need for a more complex set-up such as a MidNite Classic combined with their Clipper

    NEC regulations, btw, require redundant diversion control on turbines in case something goes wrong with one of them. Otherwise the turbine can "spin free" and really create problems.

    It is unlikely that a turbine made out of an old motor is going to give you much power or for very long. They simply are not designed to sit out in the weather and churn out power 24/7 no matter what modifications you make to them.
  • silent57
    silent57 Registered Users Posts: 2
    Re: Newbie charge controller question

    Thanks for the quick reply. The info helps a lot. I've heard of many people using treadmill motors as generators. I just wanted to save a few dollars, but maybe I should stick with a professional setup. Thanks again, I appreciate it.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,404 admin
    Re: Newbie charge controller question

    Please note--I am not a fan of small wind in general. In the right hands. There are a few vendors that make make good equipment, but one of the best installations I have read here was with DIY turbines (Chris Olsen is not your typical shade tree mechanic), and with 60-90+ foot tall towers and a really windy region, they can be a nice addition for off grid power).

    Marc's (Cariboocoot) suggestion of the Midnite controller system could be very good fit for a 48 volt turbine powering a 12 or 24 volt battery system. MPPT type charge controller can efficiently "down convert" high voltage/low current from the Panels or Turbines to low voltage/high current needed to run a battery bank.

    These are usually not cheap or small systems... And if you are looking at over 1,200 watt of average power from the battery bank and/or over a 600-1,000 AH 12 volt battery bank, you should be looking at 24 or 48 volt battery bus voltage.

    In general, if trees in your area are not "flagging" from prevailing winds, you probably do not have enough wind. Most turbines do not begin to produce any power until 10+ MPH is reached. And most turbines max out around 28-30 MPH (which, for many turbine designs, means they do not produce any useful power in very high winds as they need to shut down for protection).

    Even our own host, Northern Arizona Wind & Sun is looking for a good wind turbine that they can sell and support (by the way, the "moderators" here and the rest of the posters here are "volunteers" for the forum and have no direct connection with our host NAWS (Windsun is our Admin and is with NAWS)..
    Note: We are no longer selling wind turbines from Southwest Windpower. Unfortunately, they were not able to meet our needs and we are in the process of searching for a suitable replacement. Please email us if you have any questions.

    A note about wind generator power ratings.

    Nearly all wind generators have somewhat generous ratings, as the power output is usually specified as the MAXIMUM output. In real life you will almost always get less. Also, most people tend to over-estimate how much wind they actually get. Most wind generators require winds in the 12 to 25 MPH range - 25 MPH is Beaufort 6 - the stage where the wind starts to "whistle" on wires and structures.

    So, some quick links for you to look through:
    BB. wrote: »
    Add links about wind power:

    Wind Power Links (good forum for DIY Wind Power)
    Hugh Piggott - Scoraig Wind Electric site for tons of info (from mike90045) (added from "russ"--Like here but more wind/less solar)
    Small windpower a scam ? Survey says SO
    Truth About Skystream & SWWP
    Windmax HY-2000 2kW Wind Turbine (apparently, some vendors don't sell spare parts--just new turbines. However, the owner, Edward has been very happy with its performance from 2010-2012--BB. 5/31/2012)

    And a general DIY Solar Builder site:


    -Bill (Chris Olson's website--Real off grid with lots of power usage--even using electric stove and drier).

    In general, the recommendations for how to proceed:
    1. Conservation--Almost always cheaper to conserve power than to generate. This means measuring your power usage (kill-a-watt type meter, whole home monitoring system, etc.)
    2. Measure loads, figure out what your basic needs are and what are "optional loads" you can delay (such as washing machine, summer irrigation vs winter non-irrigation and such).
    3. Define the battery bank size
    4. Define the solar array size
    5. Define the inverter size
    6. Define the back charging system (grid+battery charger or generator+charger, etc.).
    7. Start looking at equipment that will meet your needs.
    8. Before your buy any equipment--Do a lot of paper designs. There are usually lots of trade-offs to be made, and many different ways to achieve your goals. Off grid vs Grid Tie/Backup power systems both will need a good back up generator for most applications. Generators are 'cheap to purchase" but costly to feed fuel. Sizing a generator to the battery bank/load of the system can save 50% to 75% or more in fuel costs vs getting a big old 8+ kW genset.
    9. Now look at wind turbines as a backup for poor weather (many regions simply do not have much sun during winter/poor weather season, and wind is probably the only possible option vs feeding fuel to a genset). Wind turbines need to be 60-90+ feet in the air, well above any trees/obstructions, and should be away from residences/building/places where kids play (wind turbines fail and can shed blades or even fall from towers/tower collapse). You also need to plan on (probably) accessing the turbine once a year for lubrication/inspection/tightening hardware. Also, keep in mind that if you are in an area with lots of lightning--Wind turbines are a lightning magnet (and their support electronics) and are frequently severely damaged if there is a near by or direct strike.

    Your thoughts?

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