Top 3 Autocut Charge Controller for 12V Battery

When it comes to maintaining the health and performance of a 12V battery, using the right charge controller is absolutely essential. A good autocut charge controller not only prevents overcharging and deep discharge but also extends the overall battery life while ensuring safe and efficient power management. Whether you are working with solar panels, inverters, or regular battery charging setups, having a reliable autocut system can save you from unwanted damage and costly replacements.

In this blog, we will explore the Top 3 Autocut Charge Controllers for 12V Batteries, compare their features, and help you choose the best one based on durability, efficiency, and affordability. If you are a DIY enthusiast, solar user, or just want a dependable backup power system, this guide will make your decision easier.

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Looking for a smart way to charge your 12V battery without overcharging? This project shows you how to build a DIY 12V trickle charger with an auto cut-off feature using the widely available NE555 timer IC and a few basic components.

Perfect for lead-acid batteries, this circuit will automatically stop charging when the battery reaches full voltage, extending battery life and reducing energy waste.

🔧 Components List (Line by Line)

🔧 Components List (Line by Line)

NE555 Timer IC – 1 pc

NE555 Timer IC – 1 pc

1. NE555 Timer IC – 1 pc

1N507 Diode – 1 pc

1N507 Diode – 1 pc

1. 1N507 Diode – 1 pc

1NB62 Zener Diode (6.2V) – 1 pc

1NB62 Zener Diode (6.2V) – 1 pc

1. 1NB62 Zener Diode (6.2V) – 1 pc

D36 Diode – 1 pc

D36 Diode – 1 pc

1. D36 Diode – 1 pc

10µF Electrolytic Capacitor – 1 pc

1. 10µF Electrolytic Capacitor – 1 pc

Resistor 1kΩ – 1 pc

1. Resistor 1kΩ – 1 pc

Resistor 62Ω – 1 pc

1. Resistor 62Ω – 1 pc

Resistor 4.7kΩ – 1 pc

1. Resistor 4.7kΩ – 1 pc

Resistor 10kΩ – 1 pc

1. Resistor 10kΩ – 1 pc

Resistor 12kΩ – 1 pc

1. Resistor 12kΩ – 1 pc

BC547 NPN Transistor – 1 pc

1. BC547 NPN Transistor – 1 pc

12V SPDT Relay (e.g., 650-1) – 1 pc

1. 12V SPDT Relay (e.g., 650-1) – 1 pc

Dual Color LED Indicator – 1 pc

1. Dual Color LED Indicator – 1 pc

Freewheeling Diode – 1 pc

1. Freewheeling Diode – 1 pc

15V DC Adapter or Solar Panel – 1 pc

1. 15V DC Adapter or Solar Panel – 1 pc

Optional: Terminal blocks, enclosure

1. Optional: Terminal blocks, enclosure

🧠 Circuit Overview

🧠 Circuit Overview

This project uses the NE555 IC as a voltage-level detector. When the battery voltage is below a set threshold, the output from the NE555 is high, which activates a transistor-driven relay to start charging the battery.

Once the battery is fully charged (typically around 13.7V to 14.2V), the NE555 detects the voltage via a resistor divider, switches the output low, and disconnects the charger via the relay, cutting off power to the battery.

⚙️ How It Works

⚙️ How It Works

🔌 Power Input & Regulation

🔌 Power Input & Regulation

The 15V DC input is passed through protection diodes and a Zener to stabilize the voltage.

1. The 15V DC input is passed through protection diodes and a Zener to stabilize the voltage.

This prevents reverse polarity and voltage spikes.

1. This prevents reverse polarity and voltage spikes.

🧪 NE555 Comparator Mode

🧪 NE555 Comparator Mode

Configured in comparator mode, the NE555 reads the divided battery voltage.

1. Configured in comparator mode, the NE555 reads the divided battery voltage.

If the voltage is below the threshold, the output goes HIGH, turning ON a transistor.

1. If the voltage is below the threshold, the output goes HIGH, turning ON a transistor.

🔁 Relay Control

🔁 Relay Control

The transistor switches the relay, which connects the charging source to the battery.

1. The transistor switches the relay, which connects the charging source to the battery.

A flyback diode is used to protect the transistor from voltage spikes.

1. A flyback diode is used to protect the transistor from voltage spikes.

🔋 Auto Cut-Off Logic

🔋 Auto Cut-Off Logic

Once the battery voltage exceeds the set point, the NE555 output goes LOW.

1. Once the battery voltage exceeds the set point, the NE555 output goes LOW.

The transistor switches OFF, the relay disengages, and charging stops.

1. The transistor switches OFF, the relay disengages, and charging stops.

🔎 Visual Guide

🧪 Testing

Connect your 12V lead-acid battery to the output terminal.

1. Connect your 12V lead-acid battery to the output terminal.

Power the circuit with a 15V adapter or solar panel.

1. Power the circuit with a 15V adapter or solar panel.

Observe the LED: ON = Charging, OFF = Full.

1. Observe the LED: ON = Charging, OFF = Full.

Once charged, the relay will cut the power automatically.

1. Once charged, the relay will cut the power automatically.

✅ Why This Project?

✅ Why This Project?

✔️ Protects battery from overcharging

1. ✔️ Protects battery from overcharging

✔️ Fully automatic – no manual switching

1. ✔️ Fully automatic – no manual switching

✔️ Works with solar or adapter input

1. ✔️ Works with solar or adapter input

✔️ Simple, modular, and upgradable

1. ✔️ Simple, modular, and upgradable

✔️ Ideal for UPS, inverters, and emergency battery banks

1. ✔️ Ideal for UPS, inverters, and emergency battery banks

📁 Final Thoughts

📁 Final Thoughts

This NE555-based trickle charger is a powerful little automation project for anyone managing lead-acid batteries. Whether you're running a solar setup or a DIY UPS, this build is cheap, effective, and simple to replicate.

In this post, we’ll design and build a 12V Battery Autocut Charge Controller using the ATmega328P microcontroller. The system integrates components like an LCD, a relay, and basic electronic components to effectively monitor and control battery charging. Let’s dive into the circuit design, components required, and the Arduino code for programming.

Overview of the Project

Overview of the Project

This 12V Battery Autocut Charge Controller automatically cuts off the charging when the battery reaches its full charge level. It protects the battery from overcharging, ensuring safety and efficiency. The ATmega328P serves as the brain of the circuit, controlling the relay and displaying real-time battery status on the 16x2 LCD.

Required Components

ATmega328P Microcontroller (28-pin IC Base)

1. ATmega328P Microcontroller (28-pin IC Base)

16MHz Crystal Oscillator

1. 16MHz Crystal Oscillator

10K Resistor (Pull-up for RESET)

1. 10K Resistor (Pull-up for RESET)

103 Variable Resistor (For LCD contrast adjustment)

1. 103 Variable Resistor (For LCD contrast adjustment)

Capacitors (1uF, 10uF, etc.)

1. Capacitors (1uF, 10uF, etc.)

L7805 Voltage Regulator (For 5V supply)

1. L7805 Voltage Regulator (For 5V supply)

BC547 Transistor

1. BC547 Transistor

1K Resistor

1. 1K Resistor

1N4007 Diode (Flyback protection for the relay)

1. 1N4007 Diode (Flyback protection for the relay)

Relay (5V)

1. Relay (5V)

1602 LCD Display

1. 1602 LCD Display

2-pin AC Terminal Block (Input)

1. 2-pin AC Terminal Block (Input)

LED (Indicator)

1. LED (Indicator)

Header Pins

1. Header Pins

12V Battery

1. 12V Battery

PCB manufacturing (from JLCPCB )

1. PCB manufacturing (from JLCPCB )

Circuit Diagram Explanation

Circuit Diagram Explanation

Refer to the circuit diagram above for visual guidance. The major steps are explained as follows:

Power Supply Section

A 12V DC power source is connected to the circuit via a 2-pin AC terminal block.

1. A 12V DC power source is connected to the circuit via a 2-pin AC terminal block.

The voltage regulator L7805 steps the input down to 5V for powering the ATmega328P and other components.

1. The voltage regulator L7805 steps the input down to 5V for powering the ATmega328P and other components.

Capacitors (C1 and C2) stabilize the supply voltage.

1. Capacitors (C1 and C2) stabilize the supply voltage.

Power Supply SectionA 12V DC power source is connected to the circuit via a 2-pin AC terminal block.The voltage regulator L7805 steps the input down to 5V for powering the ATmega328P and other components.Capacitors (C1 and C2) stabilize the supply voltage.

1. Power Supply SectionA 12V DC power source is connected to the circuit via a 2-pin AC terminal block.The voltage regulator L7805 steps the input down to 5V for powering the ATmega328P and other components.Capacitors (C1 and C2) stabilize the supply voltage.

ATmega328P Microcontroller

The ATmega328P is configured with a 16MHz crystal oscillator for precise timing.

1. The ATmega328P is configured with a 16MHz crystal oscillator for precise timing.

Pin PC0 (A0) reads the battery voltage through a voltage divider.

1. Pin PC0 (A0) reads the battery voltage through a voltage divider.

Digital pins control the relay and send data to the LCD.

1. Digital pins control the relay and send data to the LCD.

ATmega328P MicrocontrollerThe ATmega328P is configured with a 16MHz crystal oscillator for precise timing.Pin PC0 (A0) reads the battery voltage through a voltage divider.Digital pins control the relay and send data to the LCD.

1. ATmega328P MicrocontrollerThe ATmega328P is configured with a 16MHz crystal oscillator for precise timing.Pin PC0 (A0) reads the battery voltage through a voltage divider.Digital pins control the relay and send data to the LCD.

Relay Control

The BC547 transistor drives the relay, with the 1N4007 diode providing flyback protection.

1. The BC547 transistor drives the relay, with the 1N4007 diode providing flyback protection.

The relay toggles the charging circuit, cutting off power when the battery voltage reaches a threshold.

1. The relay toggles the charging circuit, cutting off power when the battery voltage reaches a threshold.

Relay ControlThe BC547 transistor drives the relay, with the 1N4007 diode providing flyback protection.The relay toggles the charging circuit, cutting off power when the battery voltage reaches a threshold.

1. Relay ControlThe BC547 transistor drives the relay, with the 1N4007 diode providing flyback protection.The relay toggles the charging circuit, cutting off power when the battery voltage reaches a threshold.

LCD Display

The 1602 LCD shows the real-time voltage and the charging status. A 103 variable resistor adjusts the contrast.

1. The 1602 LCD shows the real-time voltage and the charging status. A 103 variable resistor adjusts the contrast.

LCD DisplayThe 1602 LCD shows the real-time voltage and the charging status. A 103 variable resistor adjusts the contrast.

1. LCD DisplayThe 1602 LCD shows the real-time voltage and the charging status. A 103 variable resistor adjusts the contrast.

Battery Voltage Monitoring

The battery voltage is scaled using a resistor divider circuit and read by the ATmega328P ADC pin (PC0).

1. The battery voltage is scaled using a resistor divider circuit and read by the ATmega328P ADC pin (PC0).

Battery Voltage MonitoringThe battery voltage is scaled using a resistor divider circuit and read by the ATmega328P ADC pin (PC0).

1. Battery Voltage MonitoringThe battery voltage is scaled using a resistor divider circuit and read by the ATmega328P ADC pin (PC0).

PCB Design

PCB Design

For assembling the project, use JLCPCB for custom PCB manufacturing. Upload your schematic and layout files (generated using EasyEDA) to ensure high-quality and cost-effective boards.

Arduino Code for ATmega328P

Arduino Code for ATmega328P

Here’s the Arduino code to program the ATmega328P. It monitors the battery voltage and toggles the relay accordingly.

How It Works

How It Works

The circuit monitors the battery voltage using the ATmega328P's ADC pin.

1. The circuit monitors the battery voltage using the ATmega328P's ADC pin.

When the voltage exceeds the set threshold (e.g., 13.8V), the relay turns off, stopping the charging process.

1. When the voltage exceeds the set threshold (e.g., 13.8V), the relay turns off, stopping the charging process.

If the voltage drops below a minimum threshold (e.g., 12.0V), the relay turns on to resume charging.

1. If the voltage drops below a minimum threshold (e.g., 12.0V), the relay turns on to resume charging.

The 16x2 LCD displays the current voltage and the charging status, providing a user-friendly interface.

1. The 16x2 LCD displays the current voltage and the charging status, providing a user-friendly interface.

Assembling the Circuit

Video Reference:

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HW602/531 Autocut Charge Controller – Complete Guide

If you’re looking for a reliable and budget-friendly battery charging solution, then the HW602/531 Autocut Charge Controller module is one of the best options available for DIY electronics projects. This small yet powerful module ensures safe charging, automatic cut-off, and long battery life – making it perfect for solar charging systems, DIY inverters, UPS, and battery-powered projects.

🔋 What is HW602/531 Autocut Charge Controller?

The HW602/531 is a compact DC battery charging module that comes with automatic cut-off functionality. When the battery reaches full charge, the controller stops charging, protecting your battery from overcharging, overheating, and damage. Once the voltage drops below the set threshold, it automatically starts charging again.

This smart cycle improves the efficiency and lifespan of your battery, making it a must-have for 12V lead-acid, lithium-ion, or LiFePO4 batteries.

⚡ Key Features of HW602/531

✅ Automatic Cut-Off – Stops charging when the battery is full

1. ✅ Automatic Cut-Off – Stops charging when the battery is full

✅ Adjustable Voltage Settings – Set cut-off and recovery voltages as per your need

1. ✅ Adjustable Voltage Settings – Set cut-off and recovery voltages as per your need

✅ Digital Display – Shows real-time voltage for monitoring

1. ✅ Digital Display – Shows real-time voltage for monitoring

✅ Wide Compatibility – Works with 6V, 12V, 24V batteries (depending on model)

1. ✅ Wide Compatibility – Works with 6V, 12V, 24V batteries (depending on model)

✅ Compact & Easy to Use – Fits into small DIY projects and circuits

1. ✅ Compact & Easy to Use – Fits into small DIY projects and circuits

🔧 Circuit Connection of HW602/531

Connecting the module is very simple:

Input – Connect power supply (DC adapter, solar panel, or SMPS) to the IN+ and IN- terminals.

1. Input – Connect power supply (DC adapter, solar panel, or SMPS) to the IN+ and IN- terminals.

Output – Connect your battery positive and negative to the BAT+ and BAT- terminals.

1. Output – Connect your battery positive and negative to the BAT+ and BAT- terminals.

Load (optional) – Some versions support direct load connection.

1. Load (optional) – Some versions support direct load connection.

Once connected, set the cut-off voltage and recovery voltage using the module’s buttons. For example, in a 12V lead-acid battery, you can set cut-off at 14.4V and recovery at 11V.

⚙️ Applications of HW602/531 Autocut Module

🔋 DIY Battery Charger (Lead-acid or Li-ion)

1. 🔋 DIY Battery Charger (Lead-acid or Li-ion)

☀️ Solar Charging Controller

1. ☀️ Solar Charging Controller

⚡ Inverter Battery Protection

1. ⚡ Inverter Battery Protection

💡 DC Power Supply Projects

1. 💡 DC Power Supply Projects

🚗 Automotive Battery Charging

1. 🚗 Automotive Battery Charging

🌟 Advantages of Using HW602/531

Extends battery life by preventing overcharge

1. Extends battery life by preventing overcharge

Saves energy and electricity

1. Saves energy and electricity

Provides hands-free operation with automation

1. Provides hands-free operation with automation

Affordable and easily available online

1. Affordable and easily available online

Perfect for hobbyists, students, and professionals

1. Perfect for hobbyists, students, and professionals

📌 Conclusion

The HW602/531 Autocut Charge Controller is a simple yet powerful tool for anyone working with rechargeable batteries. Its automatic cut-off, adjustable voltage control, and digital display make it highly efficient and user-friendly. Whether you are making a solar charging setup, inverter, or DIY project, this module ensures your batteries are always safe and long-lasting.