Midnite Solar Kid

Saggys
Saggys Solar Expert Posts: 189 ✭✭✭
in Off Grid Solar & Battery Systems #1
Going to move to a 48 volt system this spring. Need a small charge controller that can accept 6-75 watt panels in series as my 2 small arrays are 6 panel configurations, so if I use 4 panels I will have 2 left over on each 6 panel array. The other array is a 12 panel tracker array so I could use multiples of 4 but that does not work on the 2 - 6 panel array set up. This is what Midnite Solar sizing tool has to say. I think it will work, barely....

MIDNITE SOLAR'S KID SIZING TOOL    
Temperature
C°  F° 
PV Module Data (STC)
(Found on back of module or spec sheet)
Power (Watts)
VOC (Open Circuit Voltage)
VMP (Maximum Power Point Voltage)
ISC (Short Circuit Amperage)
IMP (Maximum Power Point Amperage)
VOC Temperature Coefficient C°
(Default is -0.33%)		%
VMP Temperature Coefficient C°
(Default is -0.45%)		%
Environmental Data
Coldest Ambient Temp F°
Hottest Ambient Temp F°
Nominal Battery Voltage (Volts)                                                   48                             12                             24                             36                             48                
PV Array
Number Of Modules In Series
Number Of Parallel Strings
Total Modules
Reset
PRINT RESULTS
PV Array
Rated PV Array Power:1800Watts
Anticipated Array Power @ 98F:1705Watts
Rated PV Array Current:17.6Amps
Battery Charging Current @ 57.6 V:31.3Amps
VMP (Maximum Power Point Voltage) :102Volts
VOC (Open Circuit Voltage):130.2Volts
VMP @ -22 F°:127.2Volts
VOC @ -22 F°:153.6Volts
MNKID Selection
Max Operating Voltage150
Max Non operating VOC (HyperVOC) @ 48V Nominal Battery Voltage162
Maximum Number Of Modules In Series5
Max Allowable Output Current Per KID
Based On This Current Configuration		30
Max Allowable Wattage Per KID
Based On This Current Configuration		1752
Present PV Array Wattage Of This Configuration1800
Design Check
Max VOCMARGINAL
(HyperVOC)
Temperature The KID Will
Enter HyperVOC		-5.8 F°
Array Power (Wattage)EXCESSIVE
KIDs Required1.1
NOTE: MidNite Solar recommends a second controller be added after 1.2
WARNING: MidNite Solar makes no representation, warranty or assumption of liability regarding the use of the String Calculator. This tool uses data provided by other parties (such as PV module specs) and makes calculations based on assumptions which may or may not prove to be valid.

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Comments

  • Saggys
    Saggys Solar Expert Posts: 189 ✭✭✭
    #2
    Sorry, it did not copy and paste as anticipated, but there should be enough info.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    I am a bit confused... The work sheet says 1,800 Watts but 6x75w=450 Watts (or 2x arrays 900 Watts)... 4x arrays = 1,800 watts?

    I understand using your existing panels to support your upgraded system... See if you can buy some 200+ Watt panels at $0.50 per Watt Locally (avoid shipping charges?)... That would be 9 or few panels vs 24x 75 Watt panels to mount and wire?

    If you want to keep the existing panels, what are the Vmp/Imp/Voc/Isc rating of the panels?

    Do you have a long distance run from array to the charge controller (need high Vmp-array to keep wiring size small)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Saggys
    Saggys Solar Expert Posts: 189 ✭✭✭
    #4
    BB,

    2 individual 6 panel arrays and 1-12 panel array for a total of 24-75 watt Siemens SP75 panels. These are already mounted and wired for my current 12 volt system, just have to reconfigure at the combiner box.

    The SP75 specs: VOC 21.7, VMP 17, ISC 4.8, IMP 4.4 

    The longest run to the charge controller is about 20 feet.

    The reason for the hi VOC required is I want to use all the panels on the 6 panel arrays, these are pole mounted, The other 12 panel array is a pole mounted Wattsun tracker. Plus, -20 degrees F happens every winter.

    So 4 parallel strings of 6 panels in series with a VOC of 130.2 before adjustments for temperature and a VOC of 157.5 after adjustments.

    I do plan on upgrading my panels in the future, but not as this time, it takes a lot of time to do a code compliant install.  
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    Only "major" issue I see is that the controller will shutdown if the ambient temperature falls below -5.8F and will not restart until temperature rises above that point... Probably not a big issue--No sun=very cold panels in winter and controller shuts down (typically late night/early AM temperatures when there is no or little sun). Nice sun=Warming panels controller runs.

    -Bill

    PV Array
    Rated PV Array Power:1800Watts
    Anticipated Array Power @ 104F:1679Watts
    Rated PV Array Current:17.6Amps
    Battery Charging Current @ 57.6 V:31.3Amps
    VMP (Maximum Power Point Voltage) :102Volts
    VOC (Open Circuit Voltage):130.2Volts
    VMP @ -22 F°:127.2Volts
    VOC @ -22 F°:153.6Volts
    MNKID Selection
    Max Operating Voltage150
    Max Non operating VOC (HyperVOC) @ 48V Nominal Battery Voltage162
    Maximum Number Of Modules In Series5
    Max Allowable Output Current Per KID
    Based On This Current Configuration    		30
    Max Allowable Wattage Per KID
    Based On This Current Configuration    		1752
    Present PV Array Wattage Of This Configuration1800
    Design Check
    Max VOCMARGINAL
    (HyperVOC)
    Temperature The KID Will
    Enter HyperVOC    		-5.8 F°
    Array Power (Wattage)EXCESSIVE
    KIDs Required1.1
    NOTE: MidNite Solar recommends a second controller be added after 1.2
    doc.pdf 15.7K
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Saggys
    Saggys Solar Expert Posts: 189 ✭✭✭
    #6
    Thanks BB,

    I did not realize the controller would be off below -5,8 F, I know the chart says that but I was hoping it meant that it was above the 150VOC and would not shut off till above 162VOC?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #7
    Just to be clear (as I understand, I do not work for Midnite or NAWS), the controller will not provide solar power is the Vpanel-input is over 150 VDC.

    HyperVOC is a design that allows the controller to have "too high" of input voltage and still not be damaged (the switching transistors have a rating of 150 VDC).

    If the Vpanel is >150 VDC and under 150+Vbatt, then the transistors will not be damaged.

    150V + 12V = 162 VDC max "hyperVOC"
    150V + 48V = 198 VDC max "hyperVOC"

    The controller itself (electronics, communications, etc.) still works at >150VDC. Just will not convert solar panel power if >150VDC.

    Many higher end controllers will log the maximum voltage voltage for debugging/warranty issues.

    Here is the general information from Midnite:

    https://midnitesolar.com/pdfs/whyHyperVOC.pdf

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Saggys
    Saggys Solar Expert Posts: 189 ✭✭✭
    #8
    Thanks BB for the link and explanation.
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