Using a solar panel to charge 18650's

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bads3ctor's picture
Last seen: 7 years 1 month ago
Joined: 10/26/2012 - 11:20
Posts: 23

nickelflipper wrote:
Thanks for testing this battery box. It looks like you have found your solar charging solution.

Still interested in this one for a possible power brick replacement (i.e. 18V). So what is the T switch for the USB port? is it one of those buttons next to the USB port? Is there a printed manual link?

I had to Google-Fu a few hints plus a multimeter to figure out the switches.
Right switch:
Left switch:

Closest thing to a manual is this:

My search for how to get the 12V to 21V to work correctly got me this jewel:
DC Output: 3.6V/5V/6V/9V/12V/15V/16V/19V/21V, Max 3.3A(when need to output 12~21V, Please turn No.1 Voltage Adjuster to 9V Mode)

The 12V-21V output was putting out 5V so I was stumped until I set the “USB” switch(called the No. 1 Voltage adjuster) to “T” and then the output voltages worked as advertised and I could charge my powerbag with it set to 12V while the solar panel charged the box through the input port.

Just to clarify, I called it the USB switch because I thought it adjusted the USB voltage but I was wrong about that. From my tests it looks like the right switch sets voltage from 3.6V to 9V and if you want 12V to 21V, you set the right switch to the “T” setting and then adjust the left switch. A PITA to figure out without a manual.

nickelflipper's picture
Last seen: 3 weeks 6 days ago
Joined: 10/20/2012 - 09:31
Posts: 498
Location: Oregon

O.K. then, now that starts to make some sense about the switches. The T setting has got to be a boost mode setting. So not a buck/boost output driver, but either a buck mode driver “OR” a boost mode driver. Very interesting.

Looks like the power brick replacement could still be in play. Thanks for the detective work.


Last seen: 9 months 2 weeks ago
Joined: 06/22/2012 - 03:10
Posts: 395

I would check to see if that battery box has proper balance charging. If not i would ether not use it or use protected batteries in it.

Personally I own this one it fits my camera bag perfectly, at some point i will get some good measurements on it to see how much it looses in in the step down converter, I also have this box as well, it seemed to be a much simpler setup to me.

DBSAR's picture
Last seen: 23 hours 18 min ago
Joined: 02/11/2013 - 23:28
Posts: 6401
Location: Newfoundland, Canada

I took a couple photos today of two of my “off Grid” power systems we take on our back country camping trips and group canoe trips.

Below is a Solar system built from two 20-watt Crystalline Solar panels ( they fold face in on hinges to protect their surfaces during transportation) and a modified portable 12AH 12 Volt/300Watt 120 Volt power supply. The power supply has several 12 volt DC output ports, two 5 volt USB charging ports, and a built in 300 watt 120 volt AC inverter, front LED flashlight with its one charging port, voltage regulator, solar controller, and monitoring system, and a flexible LED top light. In the pouch attached to the back of the unit are all the 12 volt cords, adapters, connectors, etc.

Last spring on our 1-week long group camping trip this unit (along with three of the smaller ones below it) using only the 12 volt & 5 volt outputs it kept our Cellphones, GPS units, and my Nitecore I4 charging 18650s on the entire tri in the back country.

This smaller 2-Watt Solar/ 3.6AH 12 Volt system below is one of three systems we used to keep our cell phones/GPS units going for all 10 of us on the week long trip. ( along with the larger unit above to power the I4 charger, and our portable motor-pump camp shower)

I am currently building a couple more portable off-grid power systems, and may build a home made folding solar panel using a selection of the salvaged solar cells from Garden Solar lights. ( below is one of two boxes of various solar cells that could be used in series and parallel sets to produce either 5 v DC or 12 volt DC using a solar controller.

That Canadian flashlight guy & Lantern Guru -Den / DBSARlight

djozz's picture
Last seen: 5 hours 7 min ago
Joined: 09/07/2012 - 17:04
Posts: 18148
Location: Amsterdam

djozz wrote:

Inspired by Racer's solar panel I bought one too. The Levin and Poweradd panels are too expensive to import from the US into the EU, so I bought a X-Dragon 14W panel from China. I will give an impression when it arrives.

The 'XDragon' arrived two weeks ago, it works very well, in a dutch autumn sun it easily delivers 1.05A to my smarphone, and perhaps more without the charger docter clone in between. When overcast, it charges between 100 and 200mA, my phone still charges at that low current. The thing looks very well made as well.