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