MPPT 75/15, 100/20 Output Drops When Solar Power Drops

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troutm8 asked Jun 16, '24

MPPT 75/15, 100/20 Output Drops When Solar Power Drops

I have tried both models and have the same problem. The controller is connected to 12V 200Ah LiFePO4 battery, a 165W solar panel and a 12V Dometic CFX65DZ refrigerator connected to Output. The system works fine as long as the panel is providing power. With sunlight, the output to the refrigerator runs around 3.5A Once the sunlight goes away, the output is greatly reduced. It will allow LED lights that consume 0.1A, but not much more so the refrigerator turns off. The Trend graph shows the output amperage drops immediately when the solar power drops below roughly 25 watts. I have removed the jumper and have tried a variety of the output settings including Always On and the behavior is the same. When the refrigerator is connected directly to the battery, it's voltage doesn't drop below 13.1V after running all night. I have seen other people having this problem, but have not seen a solution.

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Answer 1 · 2024-06-16T20:49:24Z

kevgermany answered · Jun 16 at 08:49 PM

It's not clear what you mean by connected to output. Or where your measurements are taken and what is giving the measurements.

Please let us know what equipment is in the system, how it's connected (wiring diagram) and what the settings are on the solar controller (assuming there is one).

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Answer 2 · 2024-06-17T04:35:18Z

troutm8 answered · Jun 17 at 04:35 AM

I am not very good with this editor. Hopefully the attachments provide the detail you are looking for. My bad for using the term output when I am referring to the current outputed through the LOAD connection to the refrigerator. Does this help?

1718597969344.png (93.6 KiB)

1718598591480.png (23.7 KiB)

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Answer 3 · 2024-06-17T17:21:40Z

troutm8 answered · Jun 17 at 05:21 PM

Here is a screenshot of the Trends showing the LOAD output waking up as the PV gets sunlight:

1718644882439.jpeg (543.8 KiB)

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troutm8 commented · Jun 18 at 05:45 AM

Anyone figure out why LOAD amperage drops (0.1A) when sun sets but returns to normal (3.5A) when sun rises even though battery is full and LOAD set to Always On?

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Answer 4 · 2024-06-19T04:55:47Z

kevgermany answered · Jun 19 at 04:55 AM

Please post a screen shot of the load output settings. You'll find them by clicking on the cogwheel.

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