Solar panel voltage drops when load connect

[rrat8277]

Dear all,

I have a solar cell of 5v 200ma X10no. I connect them into series & put them into full Sun light. When I connect the battery charger & battery (12v 16mah), The power is dramatically down to 0.2 to 1.2v. Can any one help in this condition.

Thanks in advance.

 

[rajkum1987]

Its a common phenomenon that solar panel voltage drops to load voltage when connected.

The power is not lost there, just measure the current.

The voltage without load is the Voc (open circuit voltage), which is always high.

 

[D.A.(Tony)Stewart]

The power transferred is a product term function of V * I on light source ( variable current source) applied to a PV cell array.
PV's are not ideal current sources.

Therefore, when designing the battery charger you want to continually adjust the current load according to the threshold voltage to get approximately 0.6V per cell in series. If you plot the VI curve of a PV array on a log-log scale for V-I then the constant power plot is a straight diagonal line .

I suggest you compare your results to this flat line and determine the input impedance of the charger for the same V vs I input and get the load line to match the PV array maximum power curve. It is also temperature sensitive for V has large NTC value in the ballpark of -10mV/'C about room temp so temp compensation is required for optimal power harvesting.

I recall reading the optimal voltage is 0.6V per cell for some PV's.

https://www.pveducation.org/pvcdrom/modules/bypass-diodes this link goes on to suggest that parallel diodes may be added to protect wounded or defective hot spot cells where the ESR is too high.

Getting back to matching load lines, I think you want to have the load match the source impedance with drops for rising solar power in a "leaky PV" solar array. but in an ideal current source, it does not matter.