Mixing MPPT and PWM on same battery bank?

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2twisty
2twisty Solar Expert Posts: 199 ✭✭✭
in Off Grid Solar & Battery Systems #1
I have a Classic 150 that is the charge controller for my solar array. I am considering the purchase of a wind turbine that comes with a PWM charge controller. Ideally, I'd pick up a Classic Lite 150 and put it in Follow Me mode, but the funds are a bit low for that.

What problems, if any, would I experience from doing this? I'd still hook the PWM up so that the WhizBang Jr. can see the power going into the battery. I'm sure I'll wind up with the 2 charge controllers going into float at different times, etc. Is this a problem (i.e. bad for batteries) or just "less than optimal?"

My plan would be to later pick up that Classic Lite 150 when I had the money again, but it could be a while before that happens. Would I be doing substantial harm?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #2
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    Re: Mixing MPPT and PWM on same battery bank?

    What turbine and charge controller?

    Many setups like this "permanently" connect the turbine directly to the battery bank, and then use the PWM charge controller to "dump" excess current to a heating element/air or water heater/etc. Because the wind turbine cannot be "unloaded" when in medium to high wind speeds (Horizontal Axis Wind Turbines can over speed if unloaded in high winds).

    So--you can have a bit of an issue where the solar charge controller want to charge the battery (not yet floating) and the PWM controller may want to discharge the battery (floating) -- Dumping energy from both the wind turbine and the solar array (if the charge controllers "fight each other").

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • 2twisty
    2twisty Solar Expert Posts: 199 ✭✭✭
    #3
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    Re: Mixing MPPT and PWM on same battery bank?

    I'm considering one of the many units from Missouri Wind and Solar. Have not decided which unit yet, but it sounds to me like I need to just buy the turbine and rectifier and feed it into a Classic Lite in Follow Me mode.

    Question: Can the Midnite KID be slave to a classic? I may only want to buy a 600w unit, and I'm thinking of moving to 24v soon anyway -- the Kid at 24v would be able to handle the 600W.

    I'll have to look at the design of the kits they sell to see if the dump load connects to the batteries or the output of the rectifier. Might even be able to change that part, too. Just insert the dump load relay on the rectifier output rather than the battery....
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #4
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    Re: Mixing MPPT and PWM on same battery bank?

    You may not need another controller at all. I was investigating a similar setup myself a few months ago, and I _think_ you can use a solid state relay (SSR) connected to the AUX output of the classic to control the dump load. So the turbine would connect directly to the battery bank, and you'd configure the classic's AUX output to come on when the batt voltage is slightly higher than the target charge voltage. Then there are 3 ways to connect the SSR and dump loads:

    - get a 3 phase AC SSR and wire the dump loads across the phases from the turbine (this may not work well because the turbine frequency might be too high for the SSR)
    - get a DC SSR and wire it after the rectifier from the turbine
    - get a single phase AC SSR and wire it up with the output of your inverter and a regular AC load (this means that dumping is dependent on your inverter working, if it stops then dumping stops and you could get batt overvoltage)

    See the last few paragraphs here: http://www.homehydro.com/Classic%20Settings.pdf and also the classic manual's AUX section. There have been some discussions on this on the midnite forums.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: Mixing MPPT and PWM on same battery bank?

    Here's an idea: save your money and don't buy the turbine.
    Hint: Search the forum for the company involved.
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  • 2twisty
    2twisty Solar Expert Posts: 199 ✭✭✭
    #6
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    Re: Mixing MPPT and PWM on same battery bank?

    Coot,

    Please elaborate. I will search, but I have never found irrefutable proof that their current products are crap. I don't think they make the power they claim, but I do think they will make power.

    If you don't like MWANDS, then who? NAWS doesn't seem to sell any wind turbines, yet their name has "WIND" in it!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #7
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    Re: Mixing MPPT and PWM on same battery bank?

    We sort of just don't discuss MWANDS here--Pretty much every time, it goes down a black hole as people pick sides. If they do not generate the power they claim, then how much do they do they generate?

    NAWS has sold wind turbine before, and is selling some units now:

    Primus Wind Power Generators and Accessories (old Southwest Wind Power products)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Steve961
    Steve961 Solar Expert Posts: 93 ✭✭✭✭
    #8
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    Re: Mixing MPPT and PWM on same battery bank?
    2twisty wrote: »
    NAWS doesn't seem to sell any wind turbines, yet their name has "WIND" in it!

    It took me all of 20 seconds to find the wind turbines on their website.

    http://www.solar-electric.com/wind-and-water-products/wind/primus-wind-power-generators-turbines-accessories.html
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  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    #9
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    Re: Mixing MPPT and PWM on same battery bank?

    I'd be interested in an answer to the thread title, wind turbine questions aside. I have a 12V PV system with a PWM controller. Would it be possible to expand solar capacity by adding grid-tie panels and an MPPT controller, with both arrays and controllers feeding the same battery bank? Probably would be a 24V system, maybe 48V.
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  • 2twisty
    2twisty Solar Expert Posts: 199 ✭✭✭
    #10
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    Re: Mixing MPPT and PWM on same battery bank?

    Has anyone here ever purchased an MWANDS product and measured its output? I've seen plenty of videos on YouTube both for and against MWANDS, and I've never seen anyone do what I consider to be a fair and balanced test: I.E. Measure wind speed and then measure WATTS out at that speed using an agreed-upon tool like a charge controller (my Classic shows watts in....)

    The units that NAWS sells talk about how they can make 40kWh in a month, but that really doesn't help me understand what their instantaneous output is at a given wind speed. Sure, if I have 13MPH winds 24/7 for a month, I can make 40kWh? That's not much output if you divide it all out to figure what the instantaneous output is.

    Why will NOBODY produce (what seems to me) a simple chart of wind speed vs watts?
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