Description:The battery charging circuit utilizes LM317 regulators, a TL431 Zener diode, and a PNP transistor with diodes to achieve efficient and reliable charging. The LM317 regulator is set up in voltage control mode to maintain a stable output voltage of 4.2V, regardless of fluctuations in the input voltage. This stable voltage is essential for proper battery charging. The TL431 Zener diode is employed to establish the charging threshold voltage. By adjusting the potentiometer, the reference voltage can be set to around 4.16V, slightly below the maximum of 4.2V. When the battery voltage surpasses this threshold, the TL431 activates and pulls the base of the PNP transistor to the ground, turning on the transistor. This action redirects the current through the diodes and bypasses the battery, thus preventing overcharging. During operation, when a discharged battery (e.g., 3.8V) is connected to the circuit powered at 4.2V, it begins to charge while the LED indicator stays off. As the battery voltage rises and nears 4.16V, the LED lights up, indicating that charging is complete. At this point, the current flows through the diodes and transistors, which protects the battery from overvoltage. Note that while the circuit effectively provides overvoltage protection, the current limit is fixed by the resistor in the current control LM317 and must be manually adjusted if changes are required. , C , Claims:1. A smart battery balanced device (100) comprising:
i. BD140 PNP Transistor (1);
ii. TL431 Zenner reference (2);
iii. 1N4007 Diode (3);
iv. Potentiometer (4);
v. LM317 (5);
vi. Li-ion cell 3.7 V (6);
vii. Bread board (7);
viii. Resistors (1,330,10k) (8); and
ix. LED (9);
2. A smart battery balanced device (100), as claimed in Claim 1, wherein the said invention is to charging circuit worked well, charging a battery from 3.8V to 4.11V;
3. A smart battery balanced device (100) as claimed in Claim 1, wherein the said invention is circuit kept a steady 4.2V output, and when the battery reached 4.16V, the LED lit up, indicating that charging was almost done;
4. A smart battery balanced device (100) as claimed in Claim 1, wherein the said the invention, the circuit automatically stopped sending power to the battery, preventing overcharging.