How to make a mini 12 V uninterruptible power supply for a router

If there is a power outage at your home, this does not mean that the incoming electrical or fiber optic cable has lost internet. Most families have a central router at home that distributes the Internet to all mobile devices in the household. When the lights are turned off, it becomes especially sad and boring. To ensure that the Internet always works, I propose to assemble a simple uninterruptible power supply for it, which will ensure that the router operates offline for about three hours.

Will need

• Batteries 18650 series - 2 pcs - .
  
• Built-in voltmeter - .
  
• Boost Converter - .
  
• Charging module with 2S BMS protection - .
  
• Power supply 9 V 2A - .
  
• Plastic body - .

Making a mini uninterruptible power supply for a router

It was decided to take 18650 batteries from a failed laptop battery.
Let's disassemble the body.

We check that the voltage of each battery is not below 2.7 V, otherwise it will not work. Only two elements are needed.

We charge the batteries to ensure they are fully functional.

We take a plastic case. We cut holes on the side for the power supply socket and switch.

To prevent accidental short circuit of the batteries, which is very dangerous, the connection will be made through fuses.

We insulate everything with heat shrink. We fasten the elements together with electrical tape.

Cut out a window for the voltmeter.


We glue it with hot glue and use it to insulate the contacts on its board so that an accidental short circuit does not occur.

We glue the charging controller to the batteries using double-sided tape. Solder the wires to the board according to the diagram.

Uninterruptible power supply circuit on modules

We assemble a power supply circuit.

We solder a capacitor to the output to eliminate micro-surges and prevent transmission of the operating frequency of the converter.


Using a variable resistor on the boost converter, we adjust the output voltage to 12 V to power the router.

We assemble and put it on charge.

Device operation:

Previously, the router operated from its own 12 V unit. We replaced it with another, 8.4-9 Volt - this is necessary for the operation of the entire device.
So, with a working network, the power supply converts the mains voltage to 8.4-9 V, then it is supplied to a boost converter and a balanced battery charge controller. The boost converter raises the voltage to 12 V and supplies it to the router. The router is working. As soon as there is a power outage in the network, the charge controller switches its operation from charging to consumption, and a voltage from the batteries of 8.4 V appears at the output of the boost converter (if they are fully charged). And further operation of the router will be carried out from them.
Over time, the batteries will discharge and when their voltage approaches 2.7 Volts, the controller will turn off the elements, preventing them from being completely discharged.

The result of the work is as follows:

When the router consumes a current of 1 Ampere, the approximate operating time of the uninterruptible power supply is 30 minutes.

If the router consumes 0.5 Amperes, then the power will last for an hour and a half.

We measure how much our router consumes in real life.

Approximately a quarter of an Ampere, and therefore the source will ensure stable operation of the router for more than 2.5 hours.
Such a mini uninterruptible power supply can be used not only for a router, but also for a router, for a wired telephone station, for powering a removable hard drive, and for other purposes.

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