Solar panel + powerbank charging phone problem

[Asaak]

Hi all!

I have spare parts all around my place and I want to try somehting which I know it is already functioning as commercial product. Anyways, where is the funif you don't try to build it on your own?

The thing is that I have a 12V/10W solar panel:

• Open circuit voltage : 22.3V
• Max power voltage = 17.8
• Short circuit current = 0.61A
• Max power current = 0.56A

I also have this DC-DC converter


If I connect it directly to my phone under proper sunlight it works just fine. The thing is is too sensitive to sun conditions so I was wondering If I could use my Xiaomi powerbank 10400 and use its pass-through-charging feature. Again, if there is enough sunlight I can connect solar panel to dc-dc 5v usb converter and this to the micro-usb charging port of my powerbank. At the same time I can plug my phone and both the powerbank and the phone charges.
However, here comes the problem. If suddenly a cloud pass by so there is not enough light, the phone stops charging and the powerbonk doesn't start to charge it using its internal batteries as it is supposed to. It seems that when there is not enough sunlight, the voltage drops and the DC-DC converter puts 2-4V on the USB connections so the powerbank still believe that the external power charger is connected.

My question then is, if there is something to unplug the solar panel to dc-dc converter when the voltage supplied by the solar panel drops under certain voltage ( I guess, 20V which seems to be the threshold ). This way the powerbank knows there is no longer an external power source so it activates and starts powering the phone on its own.

Do you guys think it is the best to use the powerbank as a way to keep charging the phone when there is no sunlight? Apparently the most common system used is a charging controller device and lead acid battery, so this way you can charge the battery through the solar panel and use the battery to provide energy to the phone plugged. What do you guys think?

Thanks a lot!

 

[BradtheRad]

Do you know the characteristics of batteries in your phone? It is risky to attach any other charging source than the one it was designed for.

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Powerbook... powerbank

To ask a related question, what is the replacement cost if your homemade charger were to ruin your equipment?

As it appears, your plan is to hook up several items. Some are storebought, some not. I think you will need to test every item (in many ways under many conditions), before you can know what they deliver, and what they can endure.

Then you must test how they cooperate (in many ways under many conditions). Etc.

Apparently the most common system used is a charging controller device and lead acid battery, so this way you can charge the battery through the solar panel and use the battery to provide energy to the phone plugged.

The PV panel is unpredictable as you state. So, if you charge a battery from it, then that gives you a predictable power source, by means of free energy from the sun. Having constant voltage will make your design effort easier.