Introduction: Inexpensive Solar 18650 Battery Charger

About: Let's not take life too serious. Enjoy any bright spots that happen to come by.

Having recently completed my 20w solar charge controller well almost, I still have to finalize the power output. As it stands I'm able to charge such items as battery banks & cellphones via 5v usb. To charge 3.7v 18650 batteries the voltage has to be reduced from 5v. A simple matter with TP4056 lithium battery charge module.

3.7v 18650 rechargeable batteries can be purchased through a variety of distributors or salvaged from discarded laptop batteries. When the battery in a laptop can no longer keep the laptop charged properly, the fault usually lies in only one or two of the group of 18650's found bundled together to supply the needed voltage. Instead of discarding these very useful batteries they can be salvaged & used in e.g. flashlights (either diy or bought off the net), arduino or other electronic projects.

This instructable explains a simple & inexpensive way of solar charging 3.7v 18650 batteries.

Read On.....

Step 1: Parts List

In the picture above I'veincluded on the right a prior version of this project. In this earlier version I mounted the solar charge module & the battery holder onto a thick piece of plastic. This time we'll omit the plastic piece & glue the solar charge module directly to the back of the battery holder


3.7v 18650 battery holder with 6" leads from ebay roughly 50 cents to a buck - I would pay more for a more "robust" battery holder if I could find one. These are very flimsy but do the job.

TP4056 mini USB Lithium Battery Charging Board 1A 5v again about a dollar, less if you buy more than one

usb to mini or micro usb cable depending on which TP4056 charge board purchased


Hot glue gun to attach TP4056 charge board to back of battery holder & keep wires in place
Soldering iron

A word about buying from the Chinese market vs buying local. Fantastic bargains can be had when purchasing from the Chinese marketplace. How they can deliver to my door for the cost of not much more than the price of the postage in some cases mouth-watering electronic goodies is beyond my comprehension! Being new to electronics I do make many dumb mistakes, converting brand new parts into smoldering piles of useless stench! Point being even those of us on limited incomes can afford a mistake here & there when the parts are cheap to purchase.

The reasons we must buy local are many. Sure when comparing prices local can be a bit pricier. But with that bit of markup come benefits. Better packaging, faster delivery, understandable specs & instructions, better quality along with product guarantees, & what about the jobs of the people involved in manufacture & sales?

I've barely touched on this topic as it's much too large an issue to get into here. Something to keep in mind when buying parts.

Step 2: Solder Then Glue

There is very minimal soldering in this project. The positive & negative wires from the battery holder need to be soldered to the TP4056 after trimming off a couple inches from the ends of the wires. Once soldered hot glue the TP4056 module to the battery holder. Then add more hot glue to better adhere the module to the battery holder & to keep the wires firmly in place.

Please work safely being mindful of hot surfaces. Especially true for the hot glue as it can look cool to the touch when in fact it can cause a serious burn to one's probing fingertips!

Step 3: Done

Allow the glue time to harden. Doesn't take long. Attach the mini usb cable & slip in a battery that's in need of charging. While this project is all about solar charging 3.7 volt 18650 li-ion rechargeable batteries, the usb cable can be inserted anywhere 5 volts (& 500mA to 1 amp) are available - be it laptop, pc, power bar, battery bank, etc.

Thanks all for taking the time to read my instructable. Please inform me of any errors should you find any &/or any improvements you come up with. Happy Tinkering!

Step 4: Solar Charging

That's it. Since they're cheap to make it wouldn't hurt to make a couple or three.

I've entered my instructable in the MAKE ENERGY: A US-MEXICO INNOVATION CHALLENGE. A vote for my project would really be appreciated! Cast your vote at the top of this page if you please! Thanks!

Step 5: UPDATE:

Couple items

Found same board but with circuit protection on ebay for about 50 cents US apiece but you need to buy 5, I'd say that's a great deal!

If any of you like this project but don't have the time or inclination to put this together I've found on ebay someone has put together a version of this project & are selling it here for under 5bucks US.

Since posting this instructable I've found others also posted li-ion battery chargers using tp4056 here & there on the internet. Proving it's a simple, functional design worth repeating! Truth be told, they were posted before mine! lol

MAKE ENERGY: A US-Mexico Innovation Challenge

Participated in the
MAKE ENERGY: A US-Mexico Innovation Challenge