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A quick and dirty way to implement Solar switching regulator MPPT?
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fourtytwo42:
The RUN pin is very useful for preventing complete PV voltage collapse and produces a kind of burst mode at low insolations but have you tried the MPPC pin as well to try and get it to regulate it's input voltage around where you expect VMPP to be ? This would prevent it taking excessive current when greater than the run threshold but still at low light conditions. You can only select fixed values for this chip as it has no tracking function so you have to choose where you want peak efficiency then either side of that the efficiency will fall off, so for example you might optimise it for low light knowing that at higher insolations you can afford to loose some efficiency (measuring efficiency as how much power you could have got with perfect PV operating conditions vs what you actually get).
depot:
Honestly I forget how well MPPC works.

I remember a satisfied feeling about it, because the system could run continuously in bright light, but that's likely because the solar panels give more power than needed.

I think the "dark" trickle charging times are quite interesting because I live in a place with frequent rainy weather. So I think that interacts with "RUN" well, where "MPPC" is intended for finding the real high-power point.


Are there any good sources for using analog parts and a switching controller to implement MPPT?


The next thing I think I'll try is to set up LTC3355 to have two "power points" based on the resistor to set a current limit for "ICHG". Full sunlight and low sunlight power levels, and select between them based on the input voltage. And if solar power is somewhere in between, I don't think I care much if it oscillates a bit, as long as it gets some trickle charging. In the low power level, I would check less frequently than the high power level, so in any uncertain case it's going to be in the low current mode for much longer.
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