Features of digital products are growing a lot which triggers the frequent usage of smartphones in many applications. Therefore battery backup time is getting declined. The time is to make a portable power bank circuit for mobile phones as a spare charging source for emergencies. In this article, we will discover with a Great simple .
The main factor to be supposed while working with lithium batteries is protection circuits and the quality of batteries. However, when this comes to 18650 cells the risk factor is less compared with pouch batteries. Good protection is offered by a few readymade modules available in the market.
Parts required For power bank circuit
- Slide switch
Circuit Diagram of Power Bank :
Here is the circuit diagram for our power bank.
18650 Lithium Cell:
Different capacities of cells are available in the market according to the applications. A 18650 is a lithium rechargeable battery with 3.7v DC output and has between 1800mAh to 3500mAh (mili-amp-hours). There are two types of 18650 cells/batteries first one is protected and 2nd one is unprotected. Its charge time is approximately 4-6 hours. Its charge time may differ with the capacity of the cell and charger.
The method of charging a single lithium-ion cell requires two-stage,
- Constant voltage (CV)
- Constant current (CC)
The charger should supply constant current with increasing voltage until the voltage limit during CC. Next: voltage equal to the maximum limit of the cell during the current declines steadily to the lower threshold current. The TP4056 module has all these operations with great performance.
This is a very low-cost power bank charging module that can charge lithium batteries perfectly ( Mobile batteries, 18650 NMC cells, Lithium pouch batteries and etc).
This module has two indications lights RED and Blue. The red color led indicates the ongoing charging condition and the blue color LED indicates the completion of charging. This module can bear a reasonable temperature while charging. The charging current is 4.2V adjustable by charging resistor. The default current is 1A.
Micro USB 3V to 5V Boost Converter:
We need 5V to charge a cell phone but lithium battery can provide only 3.7v, so we need a booster that can convert 3V to 5V. This booster module has high efficiency to convert 3v to 5v.
This technique inside the module is a non-isolated step-up converter. By default the output power of this module is 5W. The output current can be increased till 12v but the max current will be 400MA. This module is perfect for 5v and 1A. This module has a USB female connector to attach a mobile fone cable. This module can be operated on 40 to 85 degrees centigrade. This module has A indicator LED to indicates the presence of supply.