Introduction: Pocket UPS for WiFi Router

About: Hardware design engineer who is fueled by hackathons and driven by innovation

In an emergency situation, is your commercial building or facility prepared? What would happen if a major storm hit your area with a large-scale power failure that resulted in complete loss of power? If your commercial facility is anything like many others across the nation, it is likely ill-prepared to handle a sustained power failure.In fact, most commercial facilities do not have sufficient backup power that would be necessary to keep the facility running in the event of a total power failure.

Due to the Corona virus, authorities have instructed working professionals to avoid offices and work from home. Majority of the cities world-wide have ensured a lock-down is implemented. But luckily, thanks to the internet, one can work easily. But wait! here's the problem...POWER CUTS!!

Buying an UPS might not be an affordable solution to all, instead what if we build our very own mini-UPS for our WiFi router. The reason why I decided to provide back-up to the router only is because these ADSL routers get an input from a telecom line or a fiber which is powered even during power-cuts since their units always have back-ups. Due to increased network traffic in congested metro cities, the mobile cellular data fail to provide sufficient internet bandwidth in order to connect to video conferencing calls. This eliminates the possibility of using mobile hotspots.

Finally, that leaves us to my solution.


1. 18650 batteries - 3 (3400mAh 3.7V)

2. Battery Balancer Circuit (3S 10A - HX-3S-01)

3. 2.1mm Jack male and female

Step 1: Conceal Your Hardware in an Enclosure

Since we are looking to make this circuit look like a pocket-able UPS, we must build its enclosure. Design it on having required dimensions to house three 18650 cells, battery balancer circuit and a 2.1mm jack. I designed it for 3S 18650 batteries if you want more backup time for different applications you can design it for the bigger pack by changing the z-axis height.

Please note, a plastic container would do the job too!

Step 2: Calculations and Connections

Let's do some math!

3 cells in series would give us an equivalent voltage of 11.1V (3.7V*3)

The total Watt-hour would be = 37.74Wh

Which is enough to run my 12W ADSL router for 188.7mins (37.74Wh/12W)

This is a lot of back-up time to complete your calls and get back to offline activities.

Now connect everything according to the image shown. Here you can observe that each cell's positive terminal is connected to the balancer circuit to have a proper battery balancing while charging and discharging.
Solder the 2.1mm jack to the input(INOUT-). Glue the female 2.1mm jack inside the 3D printed case. Then bring out 2.1mm male jack to connect to the router.

Connect your WiFi router/modem, sit back and relax because power cuts don't matter anymore...

There you go! your pocket UPS is ready!