UPS for Wifi Routers V3

Last year, I successfully made a router UPS v2 for my router and fibre convertor. It was able to provide two outputs at 9V and 5V with a backup time for 5 hrs.. I made this for a friend, who was facing frequent electricity cuts

He needed UPS that could support 12V 2A, in this instructables I will share how I modified my previous circuit to work as single output...

In this project i am using inexpensive, standard modules that are easily available and relatively simple to build the whole UPS

Update : After 1 month of usage, my MT3608 modules burned out. We need to replace it with better module that can handle 12V and 2A....

Alternately : Use 3S config and remove the MT3608 entirely

Update

I have been making and using DC Lithium ion battery UPS for few years now. Based on requests from friends and family, I have been modifying these circuits to support different setup and I think after 3 years, I have all the combinations as below, depending on your power requirement you can choose which version you want to make...

• Version 1 :Link (5W)
  • Single Output 9V and 0.5A
  • Can be modified to set output to 5V, but not 12V
• Version 2:Link (15W)
  • Dual Output 9V/0.5A and 5V/1.5A
  • Can be modified to supply two 5V outputs
• Version 3: This Page (24W)
  • Single output 12V/2A
  • Can be modified to step-down to 5 or 9V
• Version 4 : Link (36W)
  • Dual Output 12V and 5V
  • Output can be modified to both 5V or 9V
  • Or Single output at 12V

Step 1: What Do We Need ?

Material

• SMPS 12V 3A ( Amazon )
• Step UP converter MT3608 (Aliexpress)
• CC CV Step Down Lithium chargers XL4015 Aliexpress
• 2S Li-ion battery protection WH-2s80A ( Aliexpress)
• 18650 Li-ion batteries ( I extracted them from old laptop)
• Switch
• Wires
• 2 pin AC plug
• MDF wood for box ( I made my custom box)

Tools

• Hand Saw
• PVA glue ( Fevicol)
• Drill
• Hot Glue gun
• Soldering Iron
• Sandpaper
• Black Acrylic paint

Step 2: Circuit Diagram

We do not have any 2s lithium ion battery charging boards, like TP4056 that can supply constant voltage, current and provide battery protection on single module.

So have to break it into two

WH 2S80A: 2S 18650 battery protection, capable to divide voltage across two batteries, overcharge protection, short circuit protection etc. Battery once charged does not draw current and this module will prevent overcharging. This is key for this circuit to work as UPS

XL4015 : Is used as Li-ion charger and for 2S config we need it to provide 3A constant current and 8.4 constant voltage

Note

Green light : When Battery is completely charged and / or no current drawn from SMPS

Blue light : Current is being pulled by XL4015 to supply CC of 3A or has a load connected at the output

Step 3: Testing SMPS

Tip : It is easy to configure and troubleshoot each module separately. This prevent unwanted overload or short circuits

• Connect the SMPS to AC mains and make sure that the SMPS is supplying 12V DC
• Using Ammeter check that the SUpply is capable to provide 3A

Step 4: Config XL4015

• Connect the output from SMPS to XL4015 as input
• There are two variable resistor on the module ( as in the picture) which we need to adjust current and voltage
  • Turn Anticlock : reduces voltage / current
  • Turn Clockwise : increases voltage / current
• We need to set voltage at 8.4 first then set current to 3A
• I need 2A as output and setting 1A for charging, the batteries
• Based on the your lithium ion batteries, these value may vary. please check datasheet before setting these value

• Tip : If the variable resistors do not respond, disconnect power and turn clockwise till you hear "click" sound or the end. Note that now you have max current (5A), make sure your ammeter can take more than 5A

Step 5: 2S Li-Ion Battery

• I am using WH2S80A module as BMS for 18650 battery pack in 2s config
• Make sure that both the batteries are fulling charged
• Soldier connections as shown in circuit diagram

Step 6: Config MT3608

• Connect the Battery pack to input of MT3608
• Adjust the variable resistor to set as 12V ( Turn anticlock)
• Sometime one needs to turn several times before the voltage starts to climb

Step 7: Charge the Battery

• Connect the to the output of XL4015 and charge the batteries
• The blue led on XL4015 will turn green when the battery is fully charged
• We can test the whole circuit now and make sure that the output voltage at each module is correct
• Do not test current !!! this will cause short circuit

Step 8: The Box

• I have used 12mm MDF strip and 4mm MDF sheet for the case
• The Box is 200mm x 45mm x 110mm
• I have used PVA glue to stick the whole thing
• Drill holes for wires and switch as shown
• Paint the box with black acrylic paint and the varnish it

Step 9: Finishing

• Carefully place all the components inside the box
• Test the output again
• And then close the lid to the box
• Replace the existing power adapter with the new UPS

That's it : We are done!!!

Please share comments, questions and suggestions

Comments

[fiza786]

Hi. need some advice. We have power outages twice, sometimes thrice a day where I am. 2.5 hours at a time. I want to build a UPS using a 3s x 3p for more capacity. so 3s (12,6v) x 3p (7500mah) which will give me about a 22500mah UPS . want to make a few of them, some 12v and some 9v for my routers and mesh nodes but all single voltage output. what would be the best way to go about doing it?

[Amit_Jain]

Hi Fiza786,

If you make a single battery pack, then output is approx 12v.. you step it down to 9v
You can follow https://www.instructables.com/id/UPS-for-WiFi-Router-V4/

Just that your battery pack is 3s3p

Option B

Make multiple battery packs 3s 2p and 3s to make a 12v and a 9 v battery

[fiza786]

Hi. need some advice. We have power outages twice, sometimes thrice a day where I am. 2.5 hours at a time. I want to build a UPS using a 3s x 3p for more capacity. so 3s (12,6v) x 3p (7500mah) which will give me about a 22500mah UPS . want to make a few of them, some 12v and some 9v for my routers and mesh nodes but all single voltage output. what would be the best way to go about doing it?

[Dumfuk]

Thnku for these ups instructs. They r super helpful for a novice.

You said u had to use a WH2S80A and XL4015 in place of a TP4056. So if I used a TP4056, does that mean i dont need a bms.
Also if your power supply is putting out 12v already can u go around the modules & reconnect to the circuit at the last output jack? In some kind of parallel formation?

Thnx!

[Amit_Jain]

Tp4056 has batter protection, so you donot need a seperate BMS for single or parallel batteries. There is a limit of charging current of 1a. And for output as well. Will have to verify from the datasheet.

In ups node we have to charge and use at the same time. We cannot put batteries in parallel and series at the same time. Will cause short circuit.

I have seen a project few years back for a battery backup. Charging is done in parallel. But disconnected from charging and used in series as 12v backup using toggle switches

Share more info what you want to do...

[JulianD2]

Hi I am doing a project to automatically unlock a door with an electric motor in the door. When the door is closed I can connect 12v which is needed for the motor. However as soon as the door is opened the 12v connection will be lost and the motor still needs power to reset the lock. Can I use this solution so that the motor runs from the battery which can be charged when the door is closed.

[Amit_Jain]

If your overall requirement is 12v 2a then yes

[JulianD2]

Thanks Amit, why do you have a switch in the circuit, I assume that the battery automatically powers the router when there is a power cut?

[Amit_Jain]

I usually switch off my wifi in the night. This prevents batteries from draining by switching off

[stefanossts]

Hello. How long does the battery last for 12V v3?

[kishore007]

Hi, i have a router which needs same 12v 2a, but u said this circuit wont work for long term, can you please help with final circuit.

[Amit_Jain]

I have not shown battery connection, rest you can follow the circuit... Set current to 12.6v and constant current at 3amps

[rosekreuze]

i have made a 3s setup. but the balancer seems not working. i measured each cells individually. seems a bad bms

the only missing is the charger. can i use a laptop charger and a step down buck converter LM2506 instead of SMPS?

[Amit_Jain]

Yes. You can use laptop charger, but use XL4015 to step down with constant current settings

[johnc495]

Hi, when you say "with constant current settings", would it not be more appropriate to say a power supply with a current limit. So, I could use a 3A or an 8A supply as the batts only take what they need anyway. The load demands of course can vary.
This may seem a play of words, but when I first read about your UPS found the wording misleading "with constant current settings". In that you were relating the constant current mentioned to the typical method of charging li-ion batts.

Anyway, built it and will defo use thanks! PS. used BMS from Ebay... https://www.ebay.co.uk/itm/2S-8A-7-4V-8-4V-18650-Li-ion-Lithium-Battery-Charger-BMS-Protection-PCB-Board/254200499858?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

[rosekreuze]

sorry late reply but iv already ordered 5 lm2596 overseas and already on its way.

[Alex in NZ]

This looks really clear and do-able. Thanks for sharing your work :-)

[Amit_Jain]

You are welcome