Controller section

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Leehamrick
Leehamrick Registered Users Posts: 17 ✭
in Solar Beginners Corner #1
In another post I gave the specifications on my panel and controller.
I found out that the PWM controller that I have will not work well with the panel I intend to use.
I would like to know if this controller would be suitable for this panel.
I will be using two 12 volt deep cycle batteries
Specifications on the Panel,,

Max power 235w
Max power voltage 29.44
Max power current 8.02 A
Open circuit voltage 37.21

12 volt 24 volt
Rated solar input 20/30A 20/30A
Rated load 20/30A 20/30A
load disconnect 11.1V 22.2V
Equalization voltage 14.6V 29.2V <30 min
Boost voltage 14.4V 28.8V <30 min
Float voltage 13.6V 27.2V

And here are the specifications on a mppt controller,,
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  • Leehamrick
    Leehamrick Registered Users Posts: 17 ✭
    #2
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    Re: Controller section

    opps
    And here are the specifications on the controller,,

    Category: MPPT solar controller
    Model: MPPT30 30A
    Rated Voltage: 12V/24V
    Max Load current: 30A
    Input voltage range: 12V~20V/24V~40V
    Length≤1m Charge loop drop: ＜0.25V
    Length≤1m Discharge loop drop: ＜0.05V
    Full charge cut: 13.7V~14.4V/27.4V~28.8V
    Low voltage cut: 10.5V~11V/21V~22V
    Temperature compensation: -3mv/℃/cell
    No load loss: ≤20mA
    Max wire area: 6mm2
    Ambient temperature: -25℃—+55℃

    will this work ok?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
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    Re: Controller section

    I've pasted in your panel specs from the other post as I assume that's what you meant to have listed there.

    Those specs on the "MPPT" controller indicate it does nothing for down-converting Voltage. It wants a 12 Volt panel for 12 Volts (Input voltage range: 12V~20V) and a 24 Volt panel for 24 Volts (Input voltage range: 24~40V). I'd say it's probably a Blue Sky or a useless piece of junk from China. It would not enable you to make full use of the Vmp of 29.44 of your panel on a 12 Volt system. After that point the rest of the specs don't matter much.
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  • Leehamrick
    Leehamrick Registered Users Posts: 17 ✭
    #4
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    Re: Controller section

    Ok so what would you guys suggest? Which MPPT controller would do the job?
    If possible I would like to say at or below $100 is this possible?
    You have my attention
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: Controller section

    Under $100 for an MPPT controller? I seriously doubt you'd find a real one that would work. Under $300, yes. There's simply too many components that go in to making one to allow for low cost. The cheapest 'real' MPPT controller I know of is the MS 15 MPPT: http://www.solar-electric.com/mosumpsochco.html
    It has limitations too. For instance that one 250 Watt panel will "max out" the controller because the current potential is about 16 Amps. Although this means you would have "full" current longer than you would with less panel (the controller will simply "clip" the excess power).

    Even Blue Sky MPPT controllers are over $200, and most of them have input or output restrictions that defeat some of the reason for getting that type of controller.

    Maybe it would be cheaper in this instance to get different panels? Like two 140 Watt "true" 12 Volt panels? Example: http://www.solar-electric.com/sosp140wamum.html

    If you have to spend $300 on just a controller, the "more expensive per Watt" small panels become a better deal for a small system.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #6
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    Re: Controller section

    The "cheapest" good quality MPPT charge controllers we have seen around here are around $225-$300+ or so... The MorningStar 15 amp 12/24 volt controller has a lot of pretty good history here. And Rogue's last two models were really nice (30 amp @ 12/24 volt) and Marc has a new version that should be available this month (March 2013--the older models are not currently in production, so have to wait).

    A good number of the $100 "MPPT" Controllers out there are not. MPPT requires a fair amount of copper (inductor) and electronics for basic operation, which costs money. And many of the inexpensive "MPPT" controllers simply are PWM controllers with "MPPT" on the label.

    We are staring to read about less expensive MPPT controllers coming out of Asia, but I do not remember really seeing any reviews here yet with actual production numbers (MPPT is fairly software/hardware intensive and there are quite a few things that can go wrong--So good customer support/lots of history is a big plus).

    Also, many companies tend to have lots of options (LCD displays, somewhat expensive temperature sensors, etc.). Marc's Rogue family (at least the earlier ones) had the LCD display and basic computer connections as part of the design.

    Otherwise, for larger units (45 to 60 to 90 amp) MPPT units are going to be in the $500 to $600+ range.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: Controller section

    Just to do the math for anybody reading this thread:

    Two Solartech 140 panels @ $263 each plus one MS 20 Amp PWM controller @ $78 = $604
    One Solarworld 250 panel @ $275 plus one MS 15 Amp MPPT controller @ $224 = $499

    Difference in output current between the two: <1 Amp on 12 Volt system.
    (The 140's put out 7.8 Imp for combined current of 15.6, the 250 would be limited to 15 Amps by the controller.)

    But sometimes you can get bargains if you look around. A couple of discontinued or blemished 140 Watt panels might be had for less than $1 per Watt which would turn the tables in their favour.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #8
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    Re: Controller section

    it may also be possible to get a remanufactured classic controller as they started selling them recently over at midnight solar.
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