How to make a voltage indicator for 3.7V Li-ion and Li-Po batterys. Low and Full level indicator circuit.
Green & Red Led : https://s.click.aliexpress.com/e/_DcHLoyb
BJT NPN N5551 Transistor (BJT NPN BC548 Transistor can also be used): https://s.click.aliexpress.com/e/_DkFI9lZ or https://s.click.aliexpress.com/e/_DeEgAcj
1N4004 Diode (1N4001-4007 can also be used): https://s.click.aliexpress.com/e/_Dc65Dcf
220R resistor: https://s.click.aliexpress.com/e/_DmzbRRl
820R resistor: https://s.click.aliexpress.com/e/_DExoy3D
1K resistor: https://s.click.aliexpress.com/e/_DEb2xjN
Suitable for 1S (3.7V) LiPo and Li-ion battery.
For a 1S battery, the fully charged voltage value is 4.2V. This circuit activates the green led between 3.7V and 4.2V. This means the battery can be used. The voltage value that is considered empty is 3.3V. In order for a battery to have a long life, it should not be used at voltages below 3.3V
This indicator gives a warning between 3-7V and 3.3V by enabling both leds to be active together. When only the red led lights up, the critical level has been reached. In other words, a voltage value lower than 3.3V has been reached.
Digital Multimeter AC DC A830L : https://s.click.aliexpress.com/e/_DmjzgOJ
Digital Multimeter AC DC ANENG XL830L : https://s.click.aliexpress.com/e/_DEJiyIP
