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DIY Mini UPS for WiFi Router

A DIY uninterrupted power supply that can power up a WiFi-Router/Modem

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The pandemic COVID-19 outbreak forced companies to continue with work-from-home policy to maintain social distancing and for business continuity. More and more of us are working from home these days, and that means your home's WiFi networks are more important than ever.

Anyone with a fixed-line connection will know that their WiFi drops whenever the power goes out. It is annoying if you are in an important meeting/webinar through Zoom, WebEx, or MS-Team, and there is an interruption due to power cuts.

Features:

1. Light Weight ( 200 grams )

2. Output: 12V / 2A

3. Back up time up to 2 Hours

4. Uses 2 x 3400 mAh 18650 Battery

5. Battery Voltage Display

6. 3D Printed Enclosure

How the Circuit Work?

The working of the circuit is very simple, in normal condition, power from the mains is drawn by a 12V DC adapter to charge the 2x 18650 batteries 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. The voltmeter display is used to display the battery voltage level. The two diodes 1N5822 are used to block the reverse current flow.

In the schematic diagram, the two18650 batteries are connected in series and then they are connected to a 2S BMS board for protection during the charging and discharging.

The positive terminal input DC jack is connected to the positive terminal of the output DC jack through a Schottky diode ( 1N5822 ).

The 12V input power from the DC adapter is connected to the input terminal of the TP5100 module through a 5.5mm DC Jack. The output terminal of the TP5100 charging module is connected to the battery pack.

The battery positive terminal is connected to the boost converter LM2587 IN+ terminal through a rocker switch and the negative terminal is directly connected to the boost converter IN- terminal.

The boost converter LM2587 Out+ terminal is connected to the positive terminal of the output DC Jack through a Schottky diode ( 1N5822 ) and the Out- terminal is connected directly to the negative terminal of the DC jack.

The voltmeter positive terminal is connected to boost converter IN+ and the negative terminal is connected to IN-.


Disclaimer: Please note that you are working on a Li-Ion battery which is potentially very hazardous. I cannot be held responsible for any loss of property, damage, or loss of life if it comes to that. This tutorial is written for those who have ample knowledge of rechargeable lithium-ion technology. Please do not attempt this if you are a novice. Stay Safe.

DIY_UPS_V3.0_Main_Body.stl

3D Printed Enclosure Main Body

Standard Tesselated Geometry - 628.79 kB - 07/19/2021 at 19:24

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UPS_V3.0_TOP_Lid.stl

3D Printed Enclosure Lid

Standard Tesselated Geometry - 58.09 kB - 07/19/2021 at 19:24

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Adobe Portable Document Format - 704.73 kB - 07/19/2021 at 19:23

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Portable Network Graphics (PNG) - 305.99 kB - 07/19/2021 at 19:19

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Portable Network Graphics (PNG) - 131.19 kB - 07/19/2021 at 19:19

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  • 1 × XL4015 Module
  • 1 × XL6019 Module
  • 2 × LEDs:
  • 2 × DC Jack- Female
  • 2 × DC Jack- Male

View all 13 components

  • Version-3.0

    Debasish Dutta07/19/2021 at 19:38 0 comments

    The UPS V2.0 is upgraded to V3.0 by considering the inputs from the users.  Following are the important changes from V2.0

    1. XL4015 bulk converter is used for charging the battery pack in place of TP5100 

    2. XL6019 boost converter is used in place of ML2587

    3. 4 x 18650 batteries are used for more backup time

View project log

  • 1
    Prepare the Battery Pack:

    First, charge the two 18650 batteries by using a good charger. Here I am using a NITECORE charger.

    Clean the terminal of the 18650 battery by using a clean cloth, if required you can use fine sandpaper.

    Apply a small amount of soldering flux in all four terminals.

    Then make a series connection between the two batteries. Keep two batteries side by side, one battery positive terminal shall face towards the negative terminal of another battery. You can see the above picture for your reference. Then Join them together by using 3M double-sided tape.

    Solder a thick wire ( 20 AWG ) in the midpoint of the two batteries ( junction of the positive and negative terminal )

    Solder a black wire to the negative terminal of the first battery and red wire to the positive terminal of the second battery.

    Before soldering the wires to the BMS board, tin all the soldering pads for the good soldering joint.

    The red wire from the middle point of the battery pack is connected to the BMS MB terminal.

    The red wire is connected to BMS B+ and the black wire is connected to B-.

    At last, connect a red wire to the BMS P+ terminal and a black wire to the BMS P- terminal. These two terminals will be used for charging or discharging the battery pack.

  • 2
    Designing 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 dimensions of all the components are measured by a vernier caliper then the same were considered during the design.

    The enclosure has two parts:

    1. Main Body

    2. Cover Lid

    The Main Body is basically designed to fit all the components including the battery. The Cover lid is to cover up the main body opening.

  • 3
    Prepare the TP5100 to Charge 2S Battery Pack

    The TP5100 is a charging management module suitable for charging a single/double lithium battery (4.2V / 8.4V).

    The default setting of the board is suitable for charging a single cell ( 4.2V ) lithium battery. To set it for double cell ( 8.4V) charging, you have to short the soldering pad named as " SET ".

    Apply a small amount of solder to your soldering iron tip and then short the two soldering pad.

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Discussions

Kosma wrote 07/22/2021 at 13:43 point

in my opinion 4 separately charge and give power will be great

second idea add solar panel.

great idea

  Are you sure? yes | no

Ken Yap wrote 07/22/2021 at 14:23 point

A more general solution for people who have their own house and want to be more self-sufficient is to install solar panels and a house battery. Then you can continue with your life for some time. Doesn't help if the comms centre has a blackout though. Also this is not a cheap option but in the long run saves money.

  Are you sure? yes | no

Kosma wrote 07/22/2021 at 16:49 point

I was rather thinking about how a small device-sized panel would increase the battery life inside. And charging each cell separately will allow to use cells with different capacity (e.g. very old cells with half capacity)

  Are you sure? yes | no

Ken Yap wrote 07/14/2021 at 06:36 point

The problem though is that all the other equipment like the computer and monitor lose power in a blackout. So if a UPS is needed to keep those running, why not just power the modem/router from the same UPS?

I'd probably just fall back to a phone (or a tethered tablet) and mobile data. Fortunately these days I am NW@H, and blackouts are rare here. 😉

  Are you sure? yes | no

cirkutninja wrote 07/21/2021 at 15:53 point

While this is certainly true I think a large portion of the stay-at-home workers are utilizing laptops, myself included. So this solution is still pretty good at resolving the problem when power also takes out the router.

  Are you sure? yes | no

Ken Yap wrote 07/21/2021 at 16:35 point

Unfortunately that's not the only drawback that may occur. In my building and others the VDSL line is interfaced to fibre by equipment in the basement, and that will also lose power when there is a blackout. So potential users should look at the entire situation and not just the router's power supply.

  Are you sure? yes | no

jay wrote 07/21/2021 at 15:57 point

- The network equipment may be in a different room

- You might be working off a laptop so have no need to guy out and buy a larger UPS

- Larger lead acid battery UPS's are heavy, expensive, and take up more space

- This li-ion battery back is a DC-DC power transfer while larger UPS's convert from the lead acid battery's 12VDC to 120VAC through a sine wave generator so there is a significant waste in power in the conversion.

It doesn't take much imagination to think of plenty of use cases where a small battery pack is an ideal solution. But do we even need a reason other than building such things is fun and educational?

  Are you sure? yes | no

Ken Yap wrote 07/21/2021 at 16:37 point

See comment above.

  Are you sure? yes | no

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