Excess energy measurement

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buddhafragt asked Feb 10, '22

Excess energy measurement

Hello,
I have been thinking for a while about how a surplus energy control system could work.
I have tried a few things and have built a test circuit, which also works so far. You can see the scheme in the graphic.
The function is as follows:
ARDUINO
Turns on the relay 1 every 5 minutes for 0,5 seconds and measures the maximum available power with a test load (heater) at power meter 2.
When the battery is 90% charged + power meter 2 minus power meter 1 exceeds a certain value, relay 2 turns on an extra load. (in the Arduino the switching conditions can be easily adjusted as desired, this is just a simple example).
My questions:
Do you have any suggestions for improvement?
I have not managed to send values from the Arduino to the Venus GX and display them in the portal. How can I solve this?

MPPT Controllers Venus GX - VGX Energy Meter

leistungsmesser.jpg (122.0 KiB)

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Answer 1 · 2022-02-10T15:43:07Z

kevgermany answered · Feb 10, 2022 at 03:43 PM

Interesting. Another way would be to wait until battery 90%, then turn on the extra load. If battery starts to drop, turn off extra load. Can probably do this based on current through battery. Might need to build time delays in to prevent constant on/off etc.

Bear in mind you have an MPPT, this will self adjust depending on irradiance and load, so you may end up with conflicts. Best would be to identify the self adjust of the MPPT and check battery current immediately after. Only then disconnect extra load if needed. But I have a feeling this is too simplistic.

Maybe consider an ideal diode, like an argofet to disconnect the battery from the charge side when you connect the extra load. Battery won't go over 90%, but if you're on lithium, not a bad thing.

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Answer 2 · 2022-02-10T18:55:09Z

Mike Dorsett answered · Feb 10, 2022 at 06:55 PM

Main question is whether 0.5 seconds is enough for the MPPT's to settle at new power level...

I would put a small panel with a dump load ( about a few W) arranged so the small module is always at or below it's MPP voltage. Irradience can then be measured and averaged with an ADC. This can be compared with the expected production from the main array to control excess loads.

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Answer 3 · 2022-02-10T21:46:10Z

buddhafragt answered · Feb 10, 2022 at 09:46 PM

I think the MPPT works independently of the load, doesn't it? the MPPT should work independently of the power taken...

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