Measuring solar panel output

Projects General Guidance
1

Hey guys im currently under a project that need to measure the solar panel output voltage, current and power.
i am able to measure the short circuit current and open circuit voltage. But when i connect it to a DC load my current drop from Isc 6A to 0.4A.
i connect my current sensor in series with the solar panel. i am able to get the voltage which i connect the voltage divider in parallel to step down voltage to below 5V to read by arduino uno r3 but the current seems to be acting very weird.
i am using a buck boost converter to step down my voltage from 40V to 12V so that i can run my motor.

i am connecting 2 x 50W solar panel
specification
50W
Isc, 3.02A
Imp, 2.81A
Vmp, 17.8V
Voc, 21.9V

Voltage divider, 10k and 100kOhm resistor

Current sensor, ACS712 20A

Buck Boost converter
MingHe D3806
Input Voltage 10-40V DC
Input Current 0-8A
Output Voltage 0-38V DC
Output Current 0-6A
Conversion Efficiency >80%

Please help. HOW SHOULD MY CONNECTION BE?
My current sensor is connected before the load but only able to get 0.4A, hence my power is barely 6-9W compare to the initial 100W peak power. I'm measuring at 12noon which is perfectly sunny and bright.

Isc and Voc is correct when i measure

sorry for bad english

2

You will get more help if you draw out your wiring diagram (even hand-drawn on a sheet of paper and photographed) and post it. Please also include the specifications of the motor you are trying to power.

Perhaps you are confused between the short-circuit current and the current actually used by the motor? Does the reading of 0.4A rise if you load your motor?

3

Its extremely difficult to run a motor with just a Solar panel.
The normal way is to run the motor off a 12V battery and use the Solar Panel to charge the battery.
The start current of the motor will collapse the Solar panel voltage, as Solar Panels behave like current sources.

4

Hi,
You need to research PV panels, you are trying to use it as a voltage/potential source.

A PV is a current source and behaves differently to a potential source.

Tom... :slight_smile:
PS. A circuit of what you are attempting would help.
Post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

5

pronoobi3s:
i am using a buck boost converter to step down my voltage from 40V to 12V so that i can run my motor.

That sounds like you have 2 x 20v solar panels connected in series. If so, why not connect them in parallel?

And I agree 100% with the need to have a battery (a big battery) to even out the current.

...R