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Note: large panel (28 cells) and smaller panel (16 cells)
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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.
The DC Load was set at 30V, with the load being in constant voltage mode. At this voltage, we were NOT drawing any power
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
Solar panel output: 4A, 16.5V, P = 66 W
DC Load: 25 V, 2.4A, P = 61 W
MPPT Efficiency = 92.4%
It got slightly cloudier (for about a minute) during the same test as (2), and then got sunny again while we were taking measurements
Solar panel output: 1.2A, 18.7V, P = 22.44 W
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.
Sun was out and bright again. The film was left on
Battery pack: V = 25V, I = 2A, P = 50W
No record of solar panel output
At a similar light intensity, the film was removed
Battery pack: V = 25V, I = 2.4 A, P = 60W
We noticed that if you shade even one cell, it the current going through the batteries dropped form 2A to 1.6A
Setup: (to be added)
Stack 7 (7*4), film on: Voc = 18.6V, 4.7 A, P = 87.42W
(to be continued)