Solar charging batteries

OK guys, I’m trying to figure out how to do this and wanted to see if anyone figured it out. I want to be able to hook my 18650 charger up to a small solar panel. I have these components now but it isnt working:

Solar Panel -

Charger -

Both components work seperately but not together and I cant figure out why. They connect by a simple USB. Should be easy right? Has anyone figured this out?


Very curious to hear an answer myself on this!


I wonder if that since that panel is a ‘charger’ and not a traditional power supply, it simply can’t keep up as a charger powering a charger charging batteries.


I’m not too well versed in this subject, but it looks like your solar charger puts out the 5v necessary, but only 300mA. Your battery charger needs 5v 2A. 300mA is 0.3A


In short, you’re not providing the charger itself with enough power to even turn on most likely.

It’s almost asking too much from a dinky solar panel (with an output of 300ma) to even charge a battery through the mod (think as in while camping, or hiking), and that’s without a charger adding additional power demands on the solar supply…

Lithium batteries are basically things meant for use in the digital world.

Solar panels are intended for the analog world.
(Unless you have a very special and purpose oriented design built to accommodate a specific use scenario.)


ALL solar panels are nothing more than chargers.
(Usually the equivalent of a trickle charger)

Unless you buy a “system”, that happens to include a solar panel as part of the system as a whole, the panel itself still *only functions as a charger. :wink:


I sort of clunkily meant that. Some people have a way with words; others not have way.


Alone, you not are.


Thanks guys. What you are saying makes sense. Obviously I’m not an Electrical Engineer! What Plunderdrum said kind of explained it to me as a novice and then Sprkslfly cemented the idea (though the solar panel does turn on the charger). When you say Solar panels are meant for the analog world…it will charge my cell phone though.

I “think” I have figured out a workaround though. It seems my solar panel will charge my lipstick battery which, in turn, I can then use to charge my 18650s. I’m in the middle of testing that now. Anyway, this isn’t intended to be for everyday use, my attempt at doing this is in case of a pwer outage or “grid down” scenario. I’m certainly not powering up a generator to charge my mod! LOL!


@RusUSA… I carry a few portable power banks… from there the solar panel will keep them charged up… I don’t even plug in my cell phone to it…

with the mvp5 tho… it can charge my phone :slight_smile:

Haven’t yet gotten into solar… but I do what to take a course in it @tech one of these days… when my schedule opens up. I love to go camping and fishing… hiking… loosing myself. :wink:



I’d check what voltage and amperage the solar is putting out.


I do quite a bit of solar panel installations on a larger scale, a solar panel really is Not a charger, just like a 110 volt outlet in your house is NOT a charger.You need a controller, solar panels put out about 17 to 21VDC (times wattage based on size) the controller reduces that down to typically 12VDC and a good controller can usually increase the wattage. I suspect these small solar panels without controllers just use simple circuitry with resistors to reduce the voltage down to 5VDC and losing wattage, may be able to charge an iPhone (slowly) but not power a battery charger.:ok_hand:


Ok… Perhaps I oversimplified. (Especially given that folks here hear charger and think "the thing I put my batteries in’.)
I was trying to point out the difference between a ‘trickle charger’ and a proper power source, but failed.


Assuming it was tested in brilliant direct sunlight, I suspect it is due to the “iSmart” technology embedded into the USB port outlets. It’s designed to deliver the optimal charging current to connected devices with batteries (i.e. a mobile). It will try to “read” the connected devices requirements, and will undoubtedly have various protections (anti surge etc) which may be causing the issue.

Although the numbers appear to suggest it is possible, in a real life situation you may find yourself asking a bit too much of the solar cell.

If I was designing this from scratch I would take the native voltage from the solar cell (very probably 12v) to storage cell, then a circuit to allow the 18650’s to be charged from that.

In your case that means chopping the USB ports off your (rather beautiful)solar panel, and cracking out the soldering iron, and binning the charger etc…

Even I would be reluctant to do that, and I think given those components I would just add a USB power bank. Charge that from solar cell, then run the charger from that. They are available at 20,000mah up to 50,000, and will deliver 2.1A (so you won’t be “fast” charging 4 batteries at once).

You retain the ability to use the solar to charge your phone, and you can charge your 18650s using the charger from the power bank (charged from a wall outlet), whilst out and about, until the zombie uprising occurs.

Source: I am an electronics engineer lol


Not sure I follow this, Solar cell directly to storage cell? Add a means to precisely time the explosion and I’m sure al-Qaeda would be interested in this.

More like 20 to 22 VDC, I typically see 14V output in the shop under fluorescent lights.
Your NEED a charge controller to use solar cells to charge batteries safety, 12V battery banks are charged at 13.6 VDC the controller first bulk charges, monitors and drops down to float charge when appropriate.
Alot of vape chargers have optional 12V cord to use in vehicle, best to get a decent size 12V solar system (with controller) and go from there!

I have worked on some pretty large battery systems, Nuclear Submarines (Yeah, they are battery powered)


Literally an $.0.50 LM317, a couple of diodes and a transistor to avoid the explosion, simpler than a timer.

Thought solar cells were typically under a volt, so depends upon how the panels are constructed, no?

Small world, I’m a consultant engineer working on the electronic protection systems for a facility that supports our SSBNs.


Correct, single cell is about 1/2V, panels are most typically constructed for 12V which is 17V nominal, full sun is usually 20 to 21V

Haha yes, Former NQC inspector General Dynamics, I may have inspected some of your designs after installation if it was back in the 80’s- 90’s


I’m on the other side of the pond!


Greetings from the US,

SSBN= Submarine/submersible ballistic nuclear

HMS= Her Majesty’s Ship

TMB= Thats a my boat


Unlike Johnny5… Lucy5 was declared brain-dead and bereft of life upon arrival. Visitation will be unavailable, because there was no body. lol