Updated: Apr 8, 2019
In my locality, frequent load shading is a very common problem during the summer evening. I am really tired of this problem. I always wanted to have a mini UPS system which can power up my WiFi-Router/Modem for internet purposes and also charge my Smartphone. After some brainstorming and by using my past DIY experience, I have landed to this simple Mini UPS design . The best thing of this UPS is that it uses minimal components and it can easily fit inside my jeans pocket during the traveling.
It is capable of powering either a standard wireless router (that requires 12V DC), a Raspberry Pi/ Arduino, charging a smartphone or any 5V DC-powered device at up to 1A current
Step 1: Components and Tools Required
Components Required :
8. 18650 Battery ( Banggood )
Tools Used :
1.Soldering Iron ( Amazon )
2. Hot Glue Gun ( Amazon )
3. Wire Cutter ( Amazon )
4. Wire Stripper ( Amazon )
5. PCB Vise ( Amazon )
Step 2: How the Circuit Work?
The working of the circuit is very simple, in normal condition, power from the mains is drawn by a USB charger to charge the 18650 battery and to provide power to the router. When the mains power fails, the stored energy in the battery is used to power up the router.
In the schematic diagram, the 18650 battery is connected to a TP4056 charging module. The output of the TP4056 module is connected to the two boost converter modules: one to power the Router (12V) and another to USB Socket (5V) for smartphone charging. The output voltage of the boost converter (SX1308 module ) can be set by twisting the trimpot on the PCB board. In my case, I have set it to 12V. If your router is running at 9V, then set it to 9V. The output from the boost converter (SX1308) is connected to the external 5.5mm DC jack via an SPST switch.
Step 3: Selecting the Battery
First check the specs of your router/modem, you can get all the information on the specification sticker.
My router input power is 12V and 0.5 A. So,the power requirement for the router is 12 x 0.5 = 6W
I was considered a back up time for 30 minutes. So Watt Hour Required is = 6 x 0.5 = 3Wh
The 18650 Battery nominal voltage is 3.7V
Required Capacity = 3 Wh / 3.7V = 0.810Ah = 810mAh
The same battery also used for charging my smartphone . Let I need to charge my phone up to 35-40% for emergency use only. My Smartphone (One Plus 6) battery is rated for 3300mAh.
The final capacity required is = 810 + 3300 x0.4 = 2130 mAh
By taking the losses in the converter in to consideration, I have chosen a 3400mAh Panasonic battery for this mini UPS.
Step 4: Remove the Onboard Status LEDs
The charging status of the 18650 battery is indicated by two LEDs on the TP4056 module. My objective is that the led should be visible to the outside of the enclosure. So I desoldered the on board LEDs and soldered two 5mm LEDs ( Red and Green ).
Take fine tip soldering iron, and carefully remove the LEDs from the board by taking the help of a tweezers.
I have highlighted it in the pictures shown above.
Note: Be careful during the desoldering, otherwise you will damage the soldering pads on the PCB.
Step 5: Solder the Charging Status LEDs
I used 5mm red and green LEDs to indicate the charging status of the battery.
First I trim the legs of the LEDs as shown in the figure. The longer leg designated as the positive terminal.
Then solder 24AWG hookup wires to the LED legs. For solid connection and protection to the soldering joint, apply heat shrink tube on it.
At last, solder the LED terminal wires to the soldering pads of the onboard LEDs on the TP4056 module. The pads which are towards the TP4056 chip is negative terminals.
Step 6: Connect the 18650 Battery Holder
First, apply a small amount of solder to the B+ and B- soldering pads on the TP4056 module. Then solder the red wire of the battery holder to the B+ and black wire to the B- terminal of the TP4056 module.
Step 7: Connect the Boost Converters
Similar to the previous step, apply a small amount of solder to the Out+ and Out- terminal of TP4056 module.Then solder the wire from the Boost converters to the TP4056 Module as shown in the schematic.
VIN+ connects to Out+
GND connects to Out-
USB Boost Converter :
VIN+ connects to Out+
VIN- connects to Out-
You can see the above image for better understanding.
Step 8: Prepare the DC Jack and Switch
Solder wires to the terminal of the SPST switch and DC Jack.
The smaller leg of the DC jack is the positive terminal.
At this stage don't connect the DC jack and switch to the Boost Converter module, it will be done after installing them into the 3D printed enclosure.
Step 9: Prepare the DC Output Jack
Now you have to prepare the adapter to connect the UPS output to the router input. First check the specification of your router to confirm the size of the jack ( Sleeve size ) and the tip polarity. Your router will have a small diagram indicating the polarity expected by it; care should be taken to adhere to this, as an improper power supply may damage the device.
In my case the size of the jack is 5.5mm and the tip polarity is positive. According to the size, order two male DC Jack. Then solder red wire to the tip (smaller one ) and black wire to the sleeve.
Step 10: 3D Printed Enclosure
To give a nice commercial product look, I designed an enclosure for this project. I used Autodesk Fusion 360 to design the enclosure.
The enclosure has two parts:
1. Main Body
2. Cover Lid
The Main Body is basically designed to fit all the components including battery. The Cover lid is to cover up the main body opening.
I used my Creality CR-10S printer and 1.75 mm Grey and Red PLA filaments to print the parts. It took me about 5 hours to print the main body and around 1 hour to print the top lid.
My settings are:
Print Speed: 60 mm/s
Layer Height: 0.2mm ( 0.3 also works well)
Fill Density: 25%
Extruder Temperature: 200 deg C
Bed Temp: 60 deg C
Download the STL files from Thingiverse
Step 11: Installing the Components
Insert the components ( TP4056, Boost Converters, LEDs, Rocker Switch, and DC Jack) on the Main Body slots as shown in the picture.
At last, insert the 18650 battery inside the battery holder. Make sure you have to insert with the right polarity. The polarity is marked in the battery holder.
Finally, place the top lid and secure the 3M nuts at the corners.
Step 12: Testing and Conclusion
Plug in the UPS to standard micro USB mobile charger (5v/1A). During the charging process, the red LED will be ON and when the charge finished it will be turned off and the green LED will be switched ON.
Now connect the Mini-UPS the to router by using the adapter cable prepared in the earlier step. The router LEDs should lit up.
To test the USB port, I plugged in my smartphone, and checked the charging process by using Ampere app.
Thanks for reading my tutorial. If you like my project, don't forget to share it. Comments and feedback are always welcome.