During summer, There is frequent power cut in many areas (in India). Due to this we loss internet connectivity. So I decided to built an 12v UPS with Li-ion battery. You can find these battery in your old laptop battery or mobile power-bank.
- 3.7v Li-ion or Lipo battery x2 (18650 battery)
- LM2596 Step-Down module (buy LM2596)
- MT3608 Step-Up module (buy MT3608)
- 2s BMS (Battery Management System) (2S BMS)
- 3A schottky diode (IN5820/IN5822/SB360)
- DC male and female power jack
- Red and Black wire for connection
- Multi-meter (for testing)
Make battery bank
You can easily get 18650 Li-ion battery from old laptop battery or mobile power bank. Or can buy new from online store. first connect these battery in series. and connect 2S BMS to its Like this
Make 8.4v charger for 2S BMS
To do this we will use LM2596 step-down module (buck converter) to convert 12v to 8.4v. First connect 12v power supply to Vin pins of LM2596 module and multi-meter to Vout pins. Then rotate LM2596 potentiometer until you get 8.4v. After that connect LM2596 Vout pins to BMS P+ and P- pins. And use 3Amp schottky between +ve Pins. This will ensure to flow current in one direction only (from LM2596 to Battery bank).
Convert 8.4v from BMS to 12v
To do this we will use MT3608 step-up module (boost converter) to convert 8.4v to 12v. First connect Vin pins of MT3608 to BMS P+ and P- pins. Then connect multi-meter to Vout pins of MT3608 and rotate MT3608 potentiometer until you get 12v. After that connect DC male jack to Vout pins of MT3608.
Complete circuit diagram
You can use this setup for any DC device with input voltage between 9v to 27v. To do this rotate MT3608 potentiometer until you get your desired voltage.
Don’t use this UPS for device that use more than 1amp of current. This may overheat your modules or blowup.
It is recommenced to use heat-sink on LM2596 module.