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Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 02:16am 15 Jun 2019
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We need a nice steady constant dc load on the panel for our measurement, something that is readily adjustable over a very wide range of panel loading. And it also needs to be able to dissipate perhaps 200+ watts continuously.
The electrolytic sees a constant charging current from the panel, but a heavy intermittent pulsing discharge current of adjustable duty cycle. If the electrolytic is large enough, it will maintain a constant voltage, and present a very steady constant current load on the solar panel.
At 100% duty cycle the panel would see the full maximum 4.5 ohm load. At 10% duty cycle it would look like a constant steady 45 ohm load to the panel. At 1% duty cycle a 450 ohm load.
Just read the instantaneous watts coming from the panel, and tweak the duty cycle potentiometer for max power. You can then read the panel voltage and current that is the optimum loading under the current solar conditions. Sort of a manual do it yourself by hand mppt.
It will also demonstrate how critical (or uncritical) the whole mppt thing is. It would also be a handy little gadget to have for testing or comparing individual solar panels.
I just used what I had on hand at the time. The electrolytic is probably way bigger than it really needs to be. But for something just thrown together rather quickly as an experiment, and only ever used once, it all worked amazingly well. Edited by Warpspeed 2019-06-16Cheers, Tony.
azhaque Senior Member Joined: 21/02/2017 Location: PakistanPosts: 117
Posted: 08:00am 09 Aug 2019
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Hi all,
I am back.
Just two days before retirement I came down with Shingles. Apart from not being able to do much, I was left wondering about how the virus knew that I was about to turn 60 . Reading about Shingles on the Net tells you this fact that the Herpes virus reactivates when the host is between 50 and 60. Anybody having answers on this one please shoot .
So back to the drawing board again.
Mike. I have a question.
Although I subsequently altered the schematic, but I need you (or Tony) to please help me on the point raised by you above. My current understanding about it, is that because of the Schottky diodes installed in each panel, it seems to me that there is no need for making arrangements to stem backflow of current into the panel from the battery, after sunset.
TIA
azhaque
Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138
Posted: 08:25am 09 Aug 2019
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Shingles... Ouch, sounds bloody painful.
Just get a panel and try it, those internal diodes bypass the panel segments if shaded, they don't prevent back feed, certainly not on any of my panels any whey.
Cheers Mike
azhaque Senior Member Joined: 21/02/2017 Location: PakistanPosts: 117
Posted: 01:17pm 09 Aug 2019
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Yeah, it is indeed painful. Even the stream from a ceiling fan is painful.
The image copied below is from the page <https://www.electronics-tutorials.ws/diode/bypass-diodes.html>
I had the red diodes in my mind. You are probably referring to the green ones.
azhaque
Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138
Posted: 09:59pm 09 Aug 2019
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None of my panels have those blocking diodes in them as a default, unless you manually add them yourself, in which case then you wont require them in your controller.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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. Reading about Shingles on the Net tells you this fact that the Herpes virus reactivates when the host is between 50 and 60. Anybody having answers on this one please shoot 
.