# Solar Plane, Voltage drop when under a load [closed]

This is a project with a group of high school kids who want to be engineers. The students have built a solar power airplane. We are using maxeon solar cells.

Here is a link to the test video from yesterday. Notice the voltage drop when we start the motor. The cells are rated at .58v (Vmpp) at 6amps (Impp).

Some of the cells have minor damage due to this being a group of high school kids, so that could very well be contributing to the problem.

Here is the video, any thoughts. Static Run Up

## closed as unclear what you're asking by Olin Lathrop, laptop2d, MCG, Dmitry Grigoryev, Kevin ReidMay 23 '18 at 19:36

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• Linking to a video in your question is generally not recommended; it's better that you describe what you saw and why you think it's a problem. – Hearth May 10 '18 at 14:28
• Yeah, but then someone who wishes to see the problem or the data can see the video evidence to help devise an appropriate answer to the question. I think in this case the video is appropriate. – Paul Kaup May 10 '18 at 14:39
• Perhaps so, but consider people who, for one reason or another, can't watch the video. Maybe they're deaf, maybe they're blind, maybe they're simply busy and can't spend however long the video is watching a video, but have a few seconds to read some text. – Hearth May 10 '18 at 14:52
• What's the current draw? What's the impedance of the cells? What's the volt drop in numbers? Have you applied V=IR? – Puffafish May 10 '18 at 15:04
• Do you have any link to the cell datasheet ? .58v seems a little high for voltage at max power for silicon cells. Also : do you have an estimate of the cell temperature ? Voltage decreases as temperature increases. – Charles JOUBERT May 10 '18 at 15:10

## 1 Answer

Some of the cells have minor damage due to this being a group of high school kids, so that could very well be contributing to the problem.

Very much so! A solar cell is basically a current source shunted by a diode (the latter is what determines Voc). If a damaged (or shaded) cell has a lower maximum current, it limits the current through the entire string, which has a huge effect on Pmax.

Test the cells individually (just connect an ammeter directly across each one), and eliminate any that can't deliver the full 6A.

• Totally think that you are correct. That was my guess. This was an incredable project to learn from. Myself and the students learned a ton from this project. I so look forward to revising the design and moving onto Solar Plane V2...thank you! – Paul Kaup May 10 '18 at 17:06