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Hi.

I'm doing a lot of wilderness expeditions an needs the lightest gear possible. I want to make a solar charger (for my nitecore nb10000) that is as light as possible and has an USB output 5V and between 2 & 3A.

I'm considering buying 2 of these USB solar panels 2 x 70grams:

https://www.aliexpress.com/item/33047177046.html?spm=a2g0o.productlist.0.0.41d05a05d70gAr&algo_pvid=87608020-b1de-4a4b-b0bd-554d96f6ba2b&algo_expid=87608020-b1de-4a4b-b0bd-554d96f6ba2b-14&btsid=0b0a556f16108034779727362e6c52&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

and 1 of these USB y cables 30grams:

https://www.ebay.co.uk/itm/USB-2-0-A-Female-to-2-Dual-USB-Male-Hub-Power-Adapter-Y-Splitter-Cable-Cord/284145962396?hash=item42286b4d9c:g:xUgAAOSwiJRf~ejA

and connect them to get an USB 5V 2.4A output at a total of 170grams.

Some say it works, some say it only works if the 2 panels has the exact same output, some say it wont work, some say you can burn the weakest panel, some say you wont get the double amp output, some say you need to install a 2 or 3A voltage controler regulator module like this one :

https://www.ebay.co.uk/itm/3PCS-5V-2A-Solar-Panel-Power-Bank-USB-Charge-Voltage-Controller-Regulator-Module/202064833235?hash=item2f0c00aad3:g:JDAAAOSw3GtZxMIe

Can anyone help me what to do? Its very important that it works and doesnt break and is as light as possible, because my life depends on my gear and I have to carry everything.

Thanx

Thomas

I looked at the reference you gave and it didn't inspire much confidence. But first understand that 1.7 amps and 1700 milliamps are exactly the same thing. Next, 1700 mAh is an appropriate unit for a battery rating but is nonsense when applied to a power supply. The Isc of 1700 ma is a short circuit rating for the solar cell and tells the current which will flow if you connect a wire pos to neg of the cell. The 6.8 volts and Isc are probably the voltage and Isc generated when the cell is in bright sunlight. The 5v 1200 ma regulator sounds appropriate for the cell. What I would do is remove the the supplied 1200ma regulators from each of the 2 units, connect the 2 solar cells in parallel, each through a 2 amp or greater diode and feed this to the 2 or 3 amp voltage regulator you mention. The diodes isolate the 2 solar cells so that one cannot feed into the other in case they are not exactly matched. Use of one regulator removes any problems of 2 regulators disagreeing on the exact voltage to regulate.

Thanks Foxx. Yes I have thought about this solution, but forgot the diodes is nessesary. Thanks. The downside to this solution is that I cant use the 2 panels separate if needed. Thats one of the reasons that Im looking for a solution to parallel the 2 usb outputs. But if that is not possible or with risk, then thats how it is. Could you put 2 diodes between the panels usb and the Y-cable or will it give too much voltage drop? Do you know if you can buy diodes with low or no voltage drop? What 2 amp or greater diodes would you recommend for the panels put in parallel?

I like your idea, because it will give me the lightest possible solution.

If I decide that need to be able to use the 2 panels separate, could I then do exactly what you suggest except from removing the 2 1200mA regulators, so I can either use the 2 1200mA ports or use the single 2 to 3 amp port?

Its a little heavier but if it works gives me all the options I need.

Thanks again

Schottky diodes have substantially less voltage drop than silicon. Diode voltage drop will show up as requiring a bit brighter sunlight at the low end of the working range but it will not affect the regulated voltage in normal sunlight. I'm not going to recommend any particular diode as there are 1000's of them and availability can vary. The only things to worry about are voltage and current ratings; I would use 25v or greater 2 amps or greater. Trying to connect 2 voltage regulators in parallel is a no-no and I can only say that the results would be difficult to predict.

Thanks