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Introduction:
The 12V Battery Auto Cutoff Protection Circuit is designed to protect lead-acid or similar rechargeable batteries from overcharging, ensuring they operate safely and extend their lifespan. When charging a battery, continuous power flow after the battery reaches full capacity can lead to overheating, overcharging, and eventual damage. This circuit automatically disconnects the charging source when the battery is fully charged, preventing further current flow.
The core components of the circuit include a TL431 voltage regulator, which acts as a precision voltage sensor, and a MOSFET (IRFZ44N), which serves as a switch to control the connection between the battery and the charging input. The circuit also features LED indicators (green and red) that show the charging status, helping users easily monitor whether the battery is charging or has reached full capacity. Additionally, a diode (1N5408) ensures reverse polarity protection and voltage regulation.
This type of circuit is ideal for automotive batteries and other 12V systems where automatic cutoff and voltage monitoring are essential for safe operation.
Component Required:
| S.No | Components | Value | Qty. |
|---|---|---|---|
| 1. | Mosfet | IRFZ44N | 1 |
| 2. | Shunt Regulator | TL431 | 1 |
| 3. | Resistor | 15K, 2.2K, 1.5K 1K, 330 ohm | 1,1,1, 1,1 |
| 4. | Diode | 1N5408 | 1 |
| 5. | LED | Red, Green | 1,1 |
| 6. | Input Supply | 14V DC | - |
| 7. | Battery | 12V | - |
IRFZ44n Mosfet Pinout:
IRFZ44N Pin Configuration (TO-220 Package):
- Pin 1 - Gate (G):
The gate is the control terminal of the MOSFET. A small voltage applied to this pin (relative to the source) switches the MOSFET on, allowing current to flow between the drain and the source. - Pin 2 - Drain (D):
The drain is the terminal through which current flows into the MOSFET when it's turned on. This pin is connected to the load in a typical circuit. - Pin 3 - Source (S):
The source is the terminal through which current flows out of the MOSFET. In an N-channel MOSFET, the source is typically connected to the negative side of the circuit (ground).
Circuit Diagram:
Circuit Explain:
This 12V auto cutoff battery protection circuit is designed to automatically disconnect the battery from the charging source when it reaches full charge, preventing overcharging and extending battery life. At the core of the circuit is the TL431, a programmable shunt voltage regulator that monitors the battery voltage. When the battery is being charged, the IRFZ44N MOSFET (U1) is turned on, allowing current to flow to the battery.
A red LED (LED2) lights up during this charging phase, indicating that the battery is being charged. As the battery voltage increases and approaches the preset cutoff threshold, which is determined by the resistor network (R1, R2, R3, R4, and R5), the TL431 adjusts the voltage at its reference pin. Once the battery reaches the full charge level, the TL431 sends a signal to the gate of the MOSFET, turning it off. This stops further current flow into the battery, effectively disconnecting it from the charging source. When this happens, the green LED (LED1) lights up, signaling that the battery is fully charged and the circuit has cut off the input to prevent overcharging.
The 1N5408 diode (D1) is placed in the circuit to protect against reverse polarity and ensure proper current flow during charging. Overall, the circuit provides simple and effective battery protection by automatically controlling the charging process based on the battery's voltage.
Applications:
- Battery charging systems
- Uninterruptible Power Supplies (UPS)