How to Charge USB devices via Large Solar Panel in DC?

[cheez]

I have two panels (12V + 24V) panels in series. My only power source is DC not AC. (I don't want to go AC route)

How do I charge small electronic devices like a phone or Samsung Galaxy pad that uses either USB or USB-C? I tried to wire positive and negative wires manually to get an old iPod Touch (4th gen) to be charged from my scooter's 5V wires from the controller but it does not work.. Since that doesn't work, how am I gonna get the Galaxy pad to get the charge from battery pack or solar panel w/ step-down converter by wiring manually? I don't have the Samsung Galaxy pad yet. Planning to get one soon. Is the wiring wrong?.. or do I need special charging boards? I looked at those tiny charging circuits and they use USB as the input and battery + and - as output. That would not work as it's backwards. I need + and - as an input, and USB (or USB-C) as output, so I can charge my future Galaxy pad..



... or I could just get a $30- 40 battery bank to charge my devices but but.... how am I going to charge the battery bank? :wink: It has USB, Micro-USB, or USB-C to charge it. Would an USB female plug work? by connecting + and - ?

Anyone?

 

[JackFlorey]

How do I charge small electronic devices like a phone or Samsung Galaxy pad that uses either USB or USB-C?

Get an X volt to 12 volt DC/DC converter, then use a car USB charger.

If you have a 36V (nominal) solar array you will want a DC/DC that can handle at least a 72 volt input.

 

[harrisonpatm]

Feed the PV into a charge controller, then into a small battery bank, at least 6V. This could be separate from your main battery system, if you already have one.

Then put a + and - coming out of your battery bank into one of these:

https://www.amazon.com/HiLetgo-Module-6V-32V12V24V-Charging-Converter/dp/B07KWVL77T/ref=sr_1_7_sspa?crid=2OOJNIOFWF7W5&keywords=5v+2a+buck&qid=1667321899&qu=eyJxc2MiOiIwLjAwIiwicXNhIjoiMC4wMCIsInFzcCI6IjAuMDAifQ%3D%3D&sprefix=5v+2a+buck%2Caps%2C154&sr=8-7-spons&psc=1

Put a switch in between the buck converter and the battery, to prevent parasitic draw.

I suppose you could technically take the PV directly to the + and - of the buck converter. But it'd be rather inefficient at best, and will fry the converter at worst. Battery in the middle would be the way to go.

 

[cheez]

How do I charge small electronic devices like a phone or Samsung Galaxy pad that uses either USB or USB-C?

Get an X volt to 12 volt DC/DC converter, then use a car USB charger.

If you have a 36V (nominal) solar array you will want a DC/DC that can handle at least a 72 volt input.

Thanks for the info. I didn't know about the car USB charger. I will take that into consideration on future buying.

As for the DC-DC converter I have the 60V Input version, steps all the way down to 12 and 5V. But you don't need a 72V input converter to take 12V+24V panels...or even 2 x 24V panels. The load voltage drops down and won't go much past 60V it will still be within tolerance. But 72V converter won't hurt though. :wink:

 

[cheez]

Feed the PV into a charge controller, then into a small battery bank, at least 6V. This could be separate from your main battery system, if you already have one.

Then put a + and - coming out of your battery bank into one of these:

https://www.amazon.com/HiLetgo-Module-6V-32V12V24V-Charging-Converter/dp/B07KWVL77T/ref=sr_1_7_sspa?crid=2OOJNIOFWF7W5&keywords=5v+2a+buck&qid=1667321899&qu=eyJxc2MiOiIwLjAwIiwicXNhIjoiMC4wMCIsInFzcCI6IjAuMDAifQ%3D%3D&sprefix=5v+2a+buck%2Caps%2C154&sr=8-7-spons&psc=1

Put a switch in between the buck converter and the battery, to prevent parasitic draw.

I suppose you could technically take the PV directly to the + and - of the buck converter. But it'd be rather inefficient at best, and will fry the converter at worst. Battery in the middle would be the way to go.

Lol the link you put up there is exactly what I was looking at before I came here to check on the forum this morning.
Glad to know that is the one to get. Thanks. Price is good too.
Yeah I do have a step-down DC-DC converter (Input 60V, step down to 5V). I suppose those Solar charge controllers have USB output? I don't have those controllers. You can directly connect DC-DC converter to the solar panel as long as the voltage is within range.


cheez

 

[JackFlorey]

As for the DC-DC converter I have the 60V Input version, steps all the way down to 12 and 5V. But you don't need a 72V input converter to take 12V+24V panels...or even 2 x 24V panels. The load voltage drops down and won't go much past 60V it will still be within tolerance.

Ah, there's the rub. The voltage will drop as long as you have a load. But at some point you will disconnect the load without disconnecting the panels and poof!

Worst case is you disconnect the load one night, then the next morning sun hits the (cold) panels and you get high voltages.

To get the exact number you figure out the coldest the panels will ever be (Tlow), find out the temperature coefficient of the panels (Tc) then use this formula:

Voc_min = Voc * ( (25C-Tlow)*Tc +1)