Charging Board for Lithium-Ion Battery With Step-up to 5 Volts

I bought a couple of lithium ion 18650 batteries to power electrical projects. However, I needed something to conveniently charge and use the batteries safely. So, I used one of the inexpensive, widely available charger modules, threw in a few switches and a step-up module. With this set up, I never have to pull the battery out of the holder. I can conveniently charge with a USB cable, and the charger will stop before the battery is damaged from over-charging. I can connect it with either male or female header pins. Then because the current flows through the module, the module will shut off before the battery is drained and damaged from under-voltage. Plus, I can select either the raw battery voltage (usually 3.7volts but it goes from 4.2v down to around 3.0V), or the stable 5 volts from a small step-up module.

One important note, there is a rare chance of a Lithium-ion battery catching fire. It is rare however it is possible. So, I acquired a Lipo-bag and charge/store my batteries in there. I recommend one of those and I put the link of the one I got at the bottom of the components section. Stay safe!

Here are the components and tools you will use. I put a couple of links to one of my many favorite Canadian suppliers, and one link from Amazon.

• 18650 battery and battery holder
• 5 Volt step up regulator (link
  
• 3.7V Lithium Charger (link)
• SPDT Slide Switch (x2) (link)
• 4cm x 6cm Perf Board
• Male header pins (two pins x2) a pair of black and a pair of red
• Female header pins (two pin x2) a pair of black and a pair of red
• Hook up wire
• M2 screws (5mm long) and nuts (x2 each)

Tools:

• 2mm drill bit
• Soldering iron and Solder
• Flush cutters (link)
• Needle nose pliers
• File
• Indelible marker pens (one red and one black)
• Lipo Bag for storage and charging (link)

To mount the battery holder, I centered it by hand along the long edge of the perf board. It sticks out at either end, but I don’t mind that. I would rather that, than waste a larger board for this project which has so few components. On the underside of the board I selected two holes that would go close to the edges at either end of the battery holder and used the drill to widen the perf board hole and mark on the bottom of the battery holder. I then removed the board, and finished drilling the two holes in the holder. The two M2 screws can then be used to mount the holder and because of the round shape of the battery and the low profile of the screws, the battery easily fits without countersinking the screws.

Pins are usually bought in lengths of 40 pin. Make sure they have the 0.1 inch (2.54 mm) spacing. The male pins can be clipped to the right length with the flush cutter (or a wire cutter). In this case, two pairs of pins. I had some red pins so I have one pair of black pins and one pair of red pins.

For the female pins I only had black. To prepare them, count out the right number, the pull out the next pin (3rd pin in this case). Then cut where that pin used to be with the wire cutter, and file the cut end so it is smooth and will fit on the board next to the male pins.

In the drawings you can see one of just the main components, then one with all the connections. (Note: The colour of the wiring in the drawing does not correspond to the actual colours I used.) I won't go through how to solder, there are many tutorials on that. Just place the components on the board so that there is enough space for everything and solder the connections with the wire. The connection to ground has two female and two male pins all soldered together all in a row. The connection to the positive voltage has two (black) female and two (red) male pins are all soldered together in its own row. I placed the charger on the bottom right with the USB port out to the right side, and the on/off switch on the bottom left.

With the indelible marker, I marked the ends of the on/off switch with the red for on, and the black for off. I also marked the 5V/3.7V switch but could only fit a “5” and a “3” so I wrote on the board as well. I like to have a visual reminder on the board with red wire and red header pins for the positive voltage, and black wire and header pins for ground. I think the charge module has reverse voltage protection, but I don’t want to risk it!

I included the final pictures of the board in action with the switch off, the voltage from the fully charged battery, and the 5 volts while powering an Arduino and LED. It was a relatively beginner soldering project, but it has come in very hand.