solar control question





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  1. #1
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    Default solar control question

    Hi guys i got this solar charge controller.
    model SK20DU the only name on it
    Rated current 20A
    Rater voltage 12v/24v
    max pv voltage 50v
    max pv input power 260w 520w 24w

    i want to connect 4x solarworld sw 50 poly rma panels to the controller to charge a Royal 1150k 12v battery to runn my national luna 110 letter fridge freezer

    will this work or am i wasting my time with this controller
    if it dose work can i add another battery

    thanks

  2. #2
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    Default Re: solar control question

    Your controller is good for your 4 panels.

    Your battery will "tell" the controller it's 12v, so good.

    Your open circuit voltage on those panels are 22.1v, so you could wire the panels in one of two ways. 2x2, meaning two in series, and then those two "banks" in parallel. That will give you higher voltage (44.2v open circuit) which works better when you have less than ideal light, or you can wire them all in parallel, giving you 22.1v open circuit, with max amps. In your case this will be 2.75x4 (at 1000W/m2 test)

    If my calculations are correct, both of these conditions will not pose any risk to your controller, or your battery.

    How many batteries you want to add is not a problem. Keep them in parallel, and ensure that they are the same spec, and not too big an age gap.
    Sakkie Coetzee

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  3. #3
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    Default Re: solar control question

    thanks for the info.

  4. #4
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    Default Re: solar control question

    Should you find when you connect up and the controller cuts out within a few seconds then the oper circuit voltage is too close to the max of 50V.

    I had it once with a cheaper controller. When I changed the controller within minutes the new controller charged 100% without cutting out.

    @Sakkie - would 2 panels in series and then 2 in || giving an input of 44V not cause the controller to switch off most of the time (PWM) where 4 in || at 22V not charge a 12V battery better?

  5. #5
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    Default Re: solar control question

    Quote Originally Posted by ekkekan View Post
    Should you find when you connect up and the controller cuts out within a few seconds then the oper circuit voltage is too close to the max of 50V.

    I had it once with a cheaper controller. When I changed the controller within minutes the new controller charged 100% without cutting out.

    @Sakkie - would 2 panels in series and then 2 in || giving an input of 44V not cause the controller to switch off most of the time (PWM) where 4 in || at 22V not charge a 12V battery better?
    I'm not sure what you mean by the controller switching off at 44V input, but if you wire the batteries all in parallel and increase the current (double that of a 2 series, 2 parallel connection), you will have 4 times the loss through your cables if using the same size wire for both connections, so if you do go 4 parallel, be sure to size the battery cables appropriately.
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  6. #6
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    Default Re: solar control question

    i did a test this morning. connected two of the solar panels in parallel to the controller. the controller turned on no problem hocked up my 105 battery and the camping fridge for 2 hours
    ran fine.
    i will add another battery soon

  7. #7
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    Default Re: solar control question

    Quote Originally Posted by petermoffat View Post
    I'm not sure what you mean by the controller switching off at 44V
    Controllers get damaged very easily when the input voltage exceeds the design level. In my case the controller switched off about 4 times and can only think it was because of the input voltage.
    Higher loss in // cables is better than things not working as they should. If it was a MPPT then no problem but this is a PWM.

    Peter refer to the PM I sent icw 44V pulses vs 22V from the PWM controller.
    Last edited by ekkekan; 2019/04/10 at 09:46 PM.

  8. #8
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    Default Re: solar control question

    Quote Originally Posted by ekkekan View Post
    @Sakkie - would 2 panels in series and then 2 in || giving an input of 44V not cause the controller to switch off most of the time (PWM) where 4 in || at 22V not charge a 12V battery better?
    The 2 in series panels physically being unable to exceed 44.2v (that is why it is stated as open circuit) it won't put a 50v controller at risk. 5.8v I believe is more than enough safety margin.
    Sakkie Coetzee

    Some people say I have a "short temper"....I see it as swift and assertive reaction to Bull!

  9. #9
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    Default Re: solar control question

    Any comments on this.

    Click image for larger version. 

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  10. #10
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    Default Re: solar control question

    As much as we might look at lowering voltage drop I think it would be better to take a lead from Victron around the use of high voltage to charge a 12V battery via PWM. May be more disadvantages using 44V to charge a 12V battery than a bit more voltage drop.

    As Victron make both type of controllers here is their view.
    Click image for larger version. 

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  11. #11
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    Default Re: solar control question

    Thank for all the info guys.
    can i plug my camping fridge into the controller or is it better to run fridge off the battery using a hella socket.
    should i put a fuse on positive cable from controller to battery

  12. #12
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    Default Re: solar control question

    Quote Originally Posted by Mitchel View Post
    Thank for all the info guys.
    can i plug my camping fridge into the controller or is it better to run fridge off the battery using a hella socket.
    should i put a fuse on positive cable from controller to battery
    Most controllers have a "Load" connection

    Unless you want to make actual use of some of the features controllers have on that circuit you can connect directly to the battery (fused of course).

    Choose what would result in the shortest cable lengths and least cable clutter for your setup

    Always fuse between battery and controller on +Input line

    Your controller might be fused on the charge output to battery, if not, do fuse (in your case 25A)
    Last edited by Dungbeetle; 2019/04/28 at 06:47 AM.
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