This charger is literally wallet sized.
Its based on a simple TP4056 charger module from Mountain Electronics. I used an empty pocket flavor strip container, (roughly the same size as a SD-Card container which can also be used)
couple pieces of wire, a penny, a neodymium magnet, some shrink tube. and 20 minutes of work to put it together.
Below photo shows how tiny this portable single cell charger is, (the positive lead stores inside the container when not in use)
- #1 showing the TP4056 and the energy strip container used.
- #2 TP4056 secured in the container with 5-minute epoxy. ( i cut an opening for the micro-USB port connector in the back)
- #3 sanded & soldered a penny to the negative lead on the TP4056, (with wire through the container cover) even a washer could be used, but copper makes a better conductor.
#4 the neodymium magnet is soldered to the positive lead, with red shrink tubing insulating the wire.
Below here is the charger in use charging a 18650 cell. (using a phone wall charger and USB cord.) can use a computer USB port, Power bank, Car USB adapter, or solar panel to power it.
(In a car, i used an elastic band to hold the charger on the base of the cell to keep it in place.) I also tested this to charge my 26650 & 32650 cells and charges them fine, though it takes longer to charge the larger cells as expected with the 1000ma version TP4056 module. Either way this simple, compact LiIon charger cost pennies to build, and works.
I thought about using micro-switches and the different resistors to modify a TP4056 so it has a switchable output to charge the smaller cells, (14500, 10440, 16340, etc.) or i could just order the lower-output resistored versions from RMM and build another for my smaller cells. (since these TP4056 charger modules cost only a buck 1.25 each.) these are great for traveling or camping with limited gear space to charge my flashlight cells in the field.
I'll take ten thanks. How much did you say? Buck fifty? Seriously though very ingenious. Would you believe I have a couple of those charger boards left and I ordered for no reason some micro usb cables the other day. Its a shame I have a light to finish before I start anything else.
That’s a stroke of genius! I was stumped on how to implement these in a nice way just a few days ago.
To make it current adjustable, you could use a 10K pot in series with the resistor, something like this sticking out of the side or top of the container.
It’s a little metal can with the wire soldered to that, and the magnet held in the can by a crimp.
NOTE, if you buy a single pair, you may get magnets that are both installed in the ‘can’ with the same polarity — if so they will leap to stick to each other, round-face to round-face. Guaranteed short circuit.
If you get two pair, and swap one of each, and shrinkwrap the magnets and wire, then the faces will both be the same polarity and repel. The magnets will still leap toward each other but the face of one will be pulled toward the rear-wire-connection side of the other — and your shrinkwrap will insulate them electrically.
I used some flux and a low-power 15w soldering pencil iron, ( so to not heat up the magnet to hot and demagnetize it) the button magnets i used seemed to have a nickel or chrome coating on them and the solder flowed quite easily to them.
its a matter of not getting the magnet to hot, but just hot enough on the surface of it for solder to flow/stick. The first one i tried demagnetized it quite a bit, the second one i made sure the magnet was stuck to a steel surface to help keep the open side cool when i soldered the wire to it.
im useing the “New” TP4056, its have Battery Protection, and have battery “in” and load “out”
its alsow have a micro usb wich make it even smaller
im goin to have few more soon and i was planing to build a balance charger for 3 cells in series.