# I Current at maximum power - PV cell

1. May 25, 2016

### Imperatore

Hello there !

I got question regarding PV cell.
The current at maximum power Im calculated from current-voltage characteristic doesn't equal to the one calculated from P(Ushunt, as you can see in the attached picture. http://prnt.sc/b864hx
Furthermore, the Im from P(U) characteristic is about 2 times greater.
This is rather strange result for me. I am of the opinion, that these currents should be approximately equal. Maybe I am wrong and you will say it's nothing weird about these results.I hope so :)

2. May 25, 2016

### Simon Bridge

To understand the result you need to know how the graph was arrived at.

3. May 25, 2016

### Imperatore

It is my graph ;)

The current from P(U) is the current through the shut resistance, and Im from current-voltage characteristic shows the current without shut resistance. It is that what you mean?
In here http://www.instsani.pl/images/PV8.ht4.jpg [Broken] you can see, that these currents are equal.
Little confused now.

Last edited by a moderator: May 7, 2017
4. May 25, 2016

### Simon Bridge

OK - compare the methodology: you should find you are measuring different things, or the same thing in different circumstances.

5. May 25, 2016

### Imperatore

Is it that difference?

6. May 25, 2016

### Simon Bridge

Why not check and see if your results are consistent with standard models?

7. May 25, 2016

### Imperatore

8. May 25, 2016

### Imperatore

From that I get:
1) Characteristic U(I):
IL=ID+ISh and ISh= 0, so IL=ID=0,5
2) Characterisitic P(U):
0,5=IL=ID+1,17(it's measured ISh), so ID=-0,67 mA

sth wrong

9. May 29, 2016

### Imperatore

aby book explainig that pheno? It is written in every book I' ve examined that these two currents should be approx the same, what in my case obviously is not met.

Last edited: May 29, 2016