| Electronics > Projects, Designs, and Technical Stuff |
| CC Load to test Low Voltage/High Current Solar Cells |
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| BHopkins123:
Hello there - I am currently looking to design a variable constant current load for testing a solar cell, however these cells are unique in that they will have a Voc ranging from 0 to 1V and Isc ranging from 0 to 3A. I was originally designing a circuit based off the video Dave did in episode 102. I had been having some issues with that circuit that when I applied feedback to the opamp from the sense resistor, i would get no output from the opamp to the gate of the transistor. In trying to find out the problem for this, I found that those kinds of circuits require the DUT to have a supply voltage greater than the voltage at which you're driving your opamp. Which led me to finding a project where another individual was testing solar cells and they used some sort of large capacitor/relay/bleed resistor setup, which I am not familiar with at all. https://www.instructables.com/id/IV-Swinger-2-a-50-IV-Curve-Tracer/]See that here: [url]https://www.instructables.com/id/IV-Swinger-2-a-50-IV-Curve-Tracer/ [/url] At the end of all this, is there a way to achieve a CC load given the parameters of my cells? |
| cbc02009:
The link you share gives an IV curve for the panel, not a CC source. If you are trying to test long-term power generation, then I don't think that is what you are looking for. GreatScott on youtube has the design for a constant current load here: I've also seen some relatively cheap ones on amazon in the $20-$50 range if you search for constant current load, but I haven't tested them, so I don't know how accurate they are, or if they're any good. https://smile.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=constant+current+load Hope that helps! I'm also working on a solar project right now. |
| max_torque:
if you want you load to absorb current right down to zero volts (and are you sure this is the case?) then you're load will need a 'ground' reference that is less than zero volts, ie negative!! If say, more sensibly, you want to dump 3A at 100mV, then your load impedance clearly needs to be less (in total, including all wiring) than 33mOhm........ (which means careful design of your wiring and probably multiple control Fets and a very load value of sense resistor to avoid excessive burden voltage) |
| cbc02009:
Dave actually uses one in yesterday's mailbag video to test the USB charger: https://youtu.be/OyIgZ549D1g?t=596 |
| BHopkins123:
I'm sure it won't be 0v, maybe a few mV, I don't actually know yet. I doubt that it will be 0 volts though. |
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