Solar panel phone charging

Thread Starter

Patrick Babic

Joined Jan 23, 2019
7
Hi!
I am making a diy project, in which I will wire a 5v solar panel directly to my usb-c port on my phone. So, if the solar panel is plugged in but there is no sunshine, will my phone think the solar panel is a power output and start wasting power trying to push current through the solar panel? My phone is the Google Pixel XL.
Thanks
Patrick
 

wayneh

Joined Sep 9, 2010
16,114
Hi!
I am making a diy project, in which I will wire a 5v solar panel directly to my usb-c port on my phone. So, if the solar panel is plugged in but there is no sunshine, will my phone think the solar panel is a power output and start wasting power trying to push current through the solar panel? My phone is the Google Pixel XL.
Thanks
Patrick
I'm not 100% sure but I doubt the phone will provide power to the panel. There are devices that can be attached to a phone and will draw power from it, though, so I suppose it's possible.

But that's all moot because I don't think your panel charger is likely to work. If it's a bigger panel with a built-in regulator that holds a steady 5V, it can work. But if the panel output is a nominal 5V, that's measured under peak light without a load.
 

sghioto

Joined Dec 31, 2017
1,038
As wayneh said above depends on the panel. You could install a diode between the panel and the phone for isolation but that will drop the voltage below 5 volts. It may still charge the phone but probably slower. Some of the 5 volt panels I've seen already have the diode installed. So what panel are you thinking about?
SG
 
Last edited:

wayneh

Joined Sep 9, 2010
16,114

Thread Starter

Patrick Babic

Joined Jan 23, 2019
7
I don’t see any diode or regulator, so you may want at least a blocking diode to prevent reverse current. Use a Schottky diode, since this will have the minimum voltage drop. For example SB140.

The panel might be capable of more than 5V. I think you’ll have to experiment.
Ok, will try! Thanks!
 

Thread Starter

Patrick Babic

Joined Jan 23, 2019
7
So, I received the panel and some schottky diodes, and I started experimenting. I attached a picture of my setup. I connected the panel series with the diode and my analog amp meter. It's winter, and I live in Finland so there is just not enough sunshine. So I had to use some powerful lamps and got a short circuit current of about 11ma. That's not much because the sun is just much brighter, but I gave it a try. My Pixel XL didn't really want to charge it just said it charged and then it said it didn't and this just repeated, but it drew only about 5ma and the voltage didn't drop more than half a volt, but if I tried to charge my old phone, it charged no problem. So, what can I do about this?
Thanks
Patrick
 

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wayneh

Joined Sep 9, 2010
16,114
My Pixel XL didn't really want to charge it just said it charged and then it said it didn't and this just repeated, but it drew only about 5ma and the voltage didn't drop more than half a volt, but if I tried to charge my old phone, it charged no problem. So, what can I do about this?
The newer phone probably tries to draw a higher current and when it does, the voltage drops and it stops charging. Repeat. The older phone may be more passive and takes what it gets. I wouldn't worry too much unless you think you are simulating sunlight intensity. Solar panels really do like having full sun.

If you want to do something more, I'd suggest another panel. That one in the photo is pretty small compared to the power needs of modern phones, especially for a guy in Finland. Oh, and try it without the ammeter in place. It may be adding enough resistance to cause a reduction in charging current.

By the way, I've been to Finland! In July. I loved it except that there was no air conditioning and yet it was quite warm. The company I was working for had plants in Hanko and Jämsänkoski, up in the woods. I'll never forget how long the evening sunset lasted - hours.
 

Thread Starter

Patrick Babic

Joined Jan 23, 2019
7
The newer phone probably tries to draw a higher current and when it does, the voltage drops and it stops charging. Repeat. The older phone may be more passive and takes what it gets. I wouldn't worry too much unless you think you are simulating sunlight intensity. Solar panels really do like having full sun.

If you want to do something more, I'd suggest another panel. That one in the photo is pretty small compared to the power needs of modern phones, especially for a guy in Finland. Oh, and try it without the ammeter in place. It may be adding enough resistance to cause a reduction in charging current.

By the way, I've been to Finland! In July. I loved it except that there was no air conditioning and yet it was quite warm. The company I was working for had plants in Hanko and Jämsänkoski, up in the woods. I'll never forget how long the evening sunset lasted - hours.
Nice! Thanks for the answer. Finland is very cold in winter about -20°C in the coldest days, but summer is great! Back to the topic. I already tried it without the ampmeter, same result. My setup isn't as bright as the sun, but it's close enough for a test. A second panel is not an option for me, because I am planning on making a phone case out of this. They state on ebay that the panel could provide 160ma which would be enough, but it will probably be about 100ma in the end which still should be enough.
Thanks again!
Patrick
 

Thread Starter

Patrick Babic

Joined Jan 23, 2019
7
I received all the mandatory stuff for this project. Put it all together, and we actually got a bit of sunlight here! I went outside and pointed the panel at the sun, and it worked! No problems with pulsing. Thanks for helping me with this project ;)!

Patrick
 
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