Blue sky solar boost 50

CBHunter
CBHunter Solar Expert Posts: 39 ✭
in General Solar Power Topics #1
Need some advice here. I have a Bluesky solar boost 50 voltage controller. I'm adding some solar panels soon. Right now, I'm going in the controller at 24v to charge 12v batteries. This works fine. Now I'm addind 2 more panels, it will come to 4 solarworld 175 watts.
Should I wired them in parrallel and then series to come in at 48v?
The owners manual is confusing, there is a dip switch setting to accept 24v in and 12v out. They say nothing about a setting to accept 48v, however in the spec sheet they say that the controller can accept up to 57v input??????
HELP!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Blue sky solar boost 50

    According the the Blue Sky product blurb (PDF Download Here). You have a maximum Solar Panel Input voltage Voc = 57 volts (Voltage, open circuit)...

    You have to be careful when looking at Vmp and Voc... Over a wide range of temperatures, Vmp (on a hot day) can be about 1/2 Voc (on a very clear and cold day, and battery bank fully charged).

    So... Using that rule of tumb, if you are using "12 volt" panels (really Vmp~17 volts)... I would not put more than two "12 volt" panels in series... If you ran 4x 12 volt panels in series, you would over voltage the solar panel input to the charge controller on a cold day with a charged battery bank (probably over 60 volts Voc).

    If you have the brand/model number for the solar panels and the min/max temperatures (early morning, late afternoon) for your area--you can look up the Vmp and Voc at ~77F... And use the V per degree F/C offset for hot and cold panels (is a pain to do--but must be done to prevent damage to the charge controller).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • CBHunter
    CBHunter Solar Expert Posts: 39 ✭
    #3
    Re: Blue sky solar boost 50

    I shall do that, thanks very much!
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
    Re: Blue sky solar boost 50

    definitely do not put those pvs in series with your sb50. it shall have to be in parallel or risk blowing out the controller. you will also be near the controller's max with those 4 pvs. 4 x 4.89a = 19.56a. 19.56a x 2 for downconversion = 39.12a. 39.12a + 10% typical mppt gains = 43.032a. now that's if staying lower for nec specs that would be 40a under the nec, but the controller can output up to 50a safely and more is just self limited to that same 50a. it wouldn't make much sense to design beyond the controller's ability anyway as that would waste valueable pv power.
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