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Lithium battery Basic knowledge I

Lithium battery Basic knowledge I

May 29,2020

1. The lithium battery is a rechargeable battery: 

Generally, the full charge of the lithium battery is 4.2V, which also has other voltages. The capacity of lithium battery is xxmah, such as 1000mah, i.e. 1000mA power supply current can be used for one hour. 500mA power supply can last for 2 hours. And so on.

2. Life and charging mode of lithium battery: 

The life of lithium battery refers to the limit of the times when it is fully filled with light. Charging mode: fast charging, slow charging, trickle charging, constant current charging, etc.

3. The attention of lithium battery circuit design: 

Overcharge and over discharge of lithium battery will affect the battery life. Pay attention to the charging voltage and current of lithium battery. Then select the appropriate charging chip. Pay attention to prevent overcharge, over discharge and short circuit protection of lithium battery. After the design, it has to go through a lot of tests.

4. Design of lithium battery charging circuit: 

Tp4056 chip is selected as an example. The maximum charging current can be controlled according to the different resistance. The charging indicator can be designed, and the charging temperature can be designed, i.e. how many degrees to charge. The combination of chip dw01 and gtt8205 can protect short circuit and overcharge.

The circuit is mainly composed of the special integrated circuit dw01 for lithium battery protection, charge and discharge control mosfet1 (including two n-channel MOSFETs). The single lithium battery is connected between B + and B -, and the battery output voltage is from P + and P -. When charging, the output voltage of the charger is connected between P + and P -, and the current is from P + to B + and B - of the single battery, and then through the charge control MOSFET to p -. In the charging process, when the voltage of the single battery exceeds 4.35v, the OC pin output signal of the special integrated circuit dw01 turns off the charge control MOSFET, and the lithium battery stops charging immediately, so as to prevent the damage of the lithium battery due to overcharge.

In the process of discharge, when the voltage of single battery drops to 2.30v, the OD pin of dw01 makes the discharge control MOSFET turn off, and the lithium battery immediately stops discharging, so as to prevent the lithium battery from being damaged due to over discharge.

The CS pin of dw01 is the current detection pin. When the output is short circuited, the conduction voltage drop of the charge discharge control MOSFET increases sharply, and the CS pin voltage rises rapidly. The dw01 output signal makes the charge discharge control mosfe T is switched off quickly for over-current or short-circuit protection.