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MPPTs

29-06-2023: Preliminary MPPT Testing

The DC Load used in these experiment was Rigol DL3031 DC Electronic Load

  • Tested one of the MPPT boards using a power supply (Sparky) and load (Rigol DL3031)

  • Load set to 25V, power supply to 2A and set to ~8V (max 15V)

  • Power output around 16W, an efficiency of ~91-92%

Conditions: cloudy, no direct sun, ~22°

  • Replaced the power supply with a large solar panel

  • Voltage around 6V and current 7.78mA

  • Load: ~25V; 0.027A; 0.6-0.7W

  • Another panel connected in series, power output increased to ~0.8W

  • When the protective layer from the larger solar panel was removed, increased power output to 0.83W-1.0W

Note: large panel (28 cells) and smaller panel (16 cells)

17-07-2023 - Solar Panel Testing with MPPT

  • 23 degrees, pretty decent sun (see picture)

  • Using Stack 9 (7 cells * 4 cells) (with a bit of clouds Apple Maps that day said it was “Partly Cloudy”)

    • With the protective film Voc = 18.5V, Isc = 0.92 A, P = 17.02W

    • Without protective film, Voc = 18.7V and Isc = 1.22 A, P = 22.814 W

Setup: The positive and negative ends of Stack 9 were connected to the positive and negative terminals of the MPPT respectively. An electrolytic capacitor (the bulky ones from the DCDC board) was placed across the output (MPPT datasheet specification when testing with DC Loads), and the output was connected to the DC Load.

  1. The DC Load was set at 30V, with the load being in constant voltage mode. At this voltage, we were NOT drawing any power

  2. The sun then came back out (much brighter and beating down than when we were doing Voc and Isc tests). DC Load was set to 25V

    1. Solar panel output: 4A, 16.5V, P = 66 W

    2. DC Load: 25 V, 2.4A, P = 61 W

    3. MPPT Efficiency = 92.4%

  3. It got slightly cloudier (for about a minute) during the same test as (2), and then got sunny again while we were taking measurements

    1. Solar panel output: 1.2A, 18.7V, P = 22.44 W

    2. DC Load: 25 V, P = 50 W → wrong value since sun was coming back up. Can’t have output power more than input power

Setup: We disconnected the load from the MPPT output (consequently removed the capacitor) and instead connected a 25V battery pack to the output.

  1. Sun was out and bright again. The film was left on

    1. Battery pack: V = 25V, I = 2A, P = 50W

    2. No record of solar panel output

  2. At a similar light intensity, the film was removed

    1. Battery pack: V = 25V, I = 2.4 A, P = 60W

  3. We noticed that if you shade even one cell, it the current going through the batteries dropped form 2A to 1.6A

Stack 7 (7*4), film on, very bright day: Voc = 18.6V, Isc = 4.7 A, P = 87.42W

Setup: Stack 7 and stack 9 (each 7 cells * 4 cells) forming a combined 56 cells. Two MPPT’s were used - one MPPT for each stack. Let MPPT_9 be the MPPT connected to Stack 9 and MPPT_7 be the MPPT connected to stack 7. We connected the output negative terminal of MPPT_9 to the negative terminal of the DC Load, the output positive terminal of MPPT_9 to the output negative terminal of MPPT_7, and the output positive terminal of MPPT_7 to the positive terminal of the DC Load. Initially, we were getting a high frequency noise from the MPPT’s. This was because we forgot to replace the capacitor. When connecting to the DC Load, always place a capacitor across the MPPT output

  1. Under sunny conditions, with the film on both the stacks:

    1. DC Load: V = 50V, I = 1.898 A, P = 94.985

Setup: Same as above. Instead of connecting to a DC Load, we connected to the battery

  1. Slightly cloudly

    1. Battery pack: V = 50V, I = 0.7A, P = 40W

  2. Sun brighter

    1. Battery pack: V = 50V, I = 2A, P = 100W

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