# Current at maximum power - PV cell

• I
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 :)

Simon Bridge
Homework Helper
To understand the result you need to know how the graph was arrived at.

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

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

Simon Bridge
Homework Helper
Why not check and see if your results are consistent with standard models?

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

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: