Build a Compact WiFi UPS at Easy

In areas with frequent power outages, maintaining a stable internet connection can be a challenge. Most WiFi routers stop working as soon as the power goes out, disrupting everything from video calls to smart home systems. To solve this problem, I built a compact DIY WiFi UPS (Uninterruptible Power Supply) that gives up to 8 hours of backup using just two 18650 lithium batteries!

This UPS automatically powers your WiFi router when the electricity goes off and recharges when the power is back. It’s lightweight, affordable, and uses easily available components like the XL6009 boost converter, 3S 20A BMS, and a 0.28” voltmeter for battery monitoring.

You can use this UPS not only for your router but also for other 12V devices like CCTV cameras, small modems, or even LED lights via the 12V sockets.

Let’s build it!

1. 3x 18650 Li-ion batteries with holder
2. 1x XL6009 boost converter (adjustable 5V–35V)
3. 1x 20A 3S BMS (Battery Management System)
4. 2x 12V DC socket (for router/modem output)
5. 1x 0.28” digital voltmeter (for battery voltage display)

1. Identify the OUT+ and OUT− terminals on the XL6009 module.
2. Solder the center pin (+) of the 12V socket to OUT+.
3. Solder the outer pin (–) of the socket to OUT– (GND).
4. Use a short copper wire or jumper to strengthen the GND connection, as shown in the photo.
5. Make sure all connections are solid and insulated properly.

📌 Tip: Adjust the XL6009 output to exactly 12V using a multimeter before connecting any device.

1. Take a new 12V socket and mount it (e.g., on the case side for charging input).
2. Solder the + pin of the socket to the IN+ of the XL6009 module.
3. Solder the – pin of the socket to the IN– (GND) of the XL6009.
4. Use short wires or copper bridge for clean connections.

📌 This socket is for input power—like charging from a 12.6V charger or solar adapter.

1. Use a small drop of hot glue near the XL6009 (like beside the potentiometer) to fix the voltmeter onto the board or case—only for holding, not locking the screw.
2. Connect OUT+ of XL6009 to the V+ and V (sense) pins of the voltmeter (they’re usually internally shorted or can be bridged).
3. Connect OUT– to the voltmeter GND (–) pin.

1. Glue the 3S BMS to the backside of the case using hot glue.
2. Make sure the pads B+, B–, B1, and B2 are clearly visible.
3. From the 3-cell 18650 battery holder:
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5. Connect the first cell’s + to B+.
6. Connect the between first and second cell (middle wire) to B1.
7. Connect the between second and third cell to B2.
8. Connect the third cell’s – to B–.

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1. Design your PCB in software (like KiCad, EasyEDA, or Eagle)
2. Export Gerber files
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1. Take two wires (red for +, black for –).
2. Solder one end of red wire to P+ terminal of the BMS.
3. Solder one end of black wire to P– terminal of the BMS.
4. Solder the other ends to the IN+ and IN– pads of the previously fixed XL6009 module.
5. Ensure solder joints are clean and not touching nearby components.
6. Use short, thick wires for better current flow.

1. After completing all wiring and soldering,
2. Cut 4 pieces of 3mm acrylic sheet to fit the sides of your circuit like a box (front, back, left, right).
3. Cut 1 acrylic piece as the base plate (bottom), and 1 for the top cover.
4. Use strong glue or hot glue to fix the circuit board onto the base acrylic sheet.
5. Then glue the side panels around the base to form the box walls.

📌 This gives your DIY UPS a clean, strong, and portable enclosure.

1. Insert 3 fully charged 18650 batteries into the 3-cell holder, following correct polarity.
2. The BMS will now start supplying power to the XL6009 boost module.
3. Power up the circuit and watch the 0.28” voltmeter display.
4. Use a small screwdriver to carefully turn the potentiometer screw on the XL6009 module.
5. Adjust slowly until the voltmeter shows a stable 12.0V output.
6. Once set, avoid touching the potentiometer again to keep the output fixed.

📌 Always check output with a multimeter if voltmeter is not calibrated.

1. Fix the completed UPS on the wall near your router/modem using screws, tape, or wall hooks.
2. Make sure the ventilation is clear and sockets are accessible.
3. Disconnect your router’s original 12V adapter from the power input.
4. Plug that 12V adapter into the input socket of your UPS (to charge the batteries).
5. Use a 12V male-to-male DC cable to connect the UPS output socket to your router’s power input port.
6. Now, when the main power is ON, the router runs normally and batteries charge.
7. During power cuts, the UPS instantly powers the router from batteries (12V output remains stable).

📌 Test backup time by removing adapter plug—router should stay ON without any delay.

Benefits of This DIY WiFi UPS:

1. Keeps your WiFi router or modem powered during power cuts—no internet disconnection.
2. Uses rechargeable 18650 batteries – eco-friendly and easily replaceable.
3. Built-in BMS protects against overcharge, over-discharge, and short circuit.
4. Boost converter gives stable 12V output for routers, cameras, or small 12V devices.
5. Compact, wall-mountable design made with acrylic—safe, clean, and portable.
6. Affordable and easy to build with basic tools and common parts.

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Watch the Demo Video:

See it in action and learn how it works!

📺 [CLICK HERE]