Hello everyone, thanks for reading this thread.

For a few days now, I am struggling with getting my solar powered, 5V charger to work.
I am using 2 of these panels from which I removed the dc-dc converter, so the data on the image is correct. Not the data in the description.

Based on a previous thread I posted, I wire them in series. The open circuit voltage easily reaches say 8-10V in the sun. Which made me decide to hook that up to a dc-dc buck converter with a min input of 6V and a USB output of 5.1V with a max of 2A. Seems fine to charge a powerbank.
Now while this sounded nice to me, in reality when a load (powerbank) is connected. The voltage from the solar cells across the input of the dc-dc converter decreases to only 4.1V which hardly charges anything. The current seems reasonable.

So why this massive drop in voltage that causes it to drop below the minimum rating of the converter? I am probably missing a basic insight here. Is there anybody that can explain me this solar panel behavior and maybe come up with a nice solution? Would be highly appreciated! Thanks in advance.

PS I have some different dc-dc converters at hand, and don't mind 1 extra solar panel if it is needed.

 

I found this only is the case with one of my powerbanks. The rest does nicely charge at 5V. How can this be?

 

I found this only is the case with one of my powerbanks. The rest does nicely charge at 5V. How can this be?

The load on the cells will drop the voltage. Apparently one of the devices is drawing too much current. A third cell might be enough to deal with the load.

 

If you leave it charging does it eventually go up to 5V?

 

The open circuit voltage easily reaches say 8-10V in the sun

Seems rather low. According to the specs each panel should deliver 7.2 volts with no load in full sun.
You should be reading at least 14 volts with two panels in series.
Panels are rated 6 volts at 1 amp in full sun.
So either the panels are defective or not getting enough sunlight.
SG

 

Those panels were designed for 5V output... do you have them wired in parallel? Doesn't look like you need regulator for it if you go parallel. Nevermind you wires in series and removed the converter.... Why not just wire two in parallel with the built in converters?

 

Those panels were designed for 5V output... do you have them wired in parallel? Doesn't look like you need regulator for it if you go parallel. Nevermind you wires in series and removed the converter.... Why not just wire two in parallel with the built in converters?

View attachment 173444

You are correct. After all I should have done that haha. But "after all" doesn't get me anywhere now...

 

Seems rather low. According to the specs each panel should deliver 7.2 volts with no load in full sun.
You should be reading at least 14 volts with two panels in series.
Panels are rated 6 volts at 1 amp in full sun.
So either the panels are defective or not getting enough sunlight.
SG

Yes that's right. As there is no sun in the Netherlands at the moment I couldn't test it. But I am 100% sure the panels are working. Easily reached 12.5V in semi-sun.