DIY Smart Battery Charger

In the world of electronics, ensuring a safe and efficient charging process is essential for maximizing battery life and performance. The 12V Hyper Battery Charger is designed to deliver precise voltage control, automatic charge regulation, and built-in protection mechanisms, making it a smart and reliable solution for charging 12V batteries.

It intelligently manages the charging process, preventing overcharging and excessive current flow, while LED indicators and a buzzer notify the user about the charging status. With an adjustable auto cut-off voltage, this charger supports Li-ion, lead-acid, and LiFePO4 battery packs, ensuring optimal charging for various battery types.

Whether for automotive batteries, backup power systems, or renewable energy storage, this charger is built to enhance battery longevity and safety. With a focus on efficiency, protection, and user-friendly operation, the 12V Hyper Battery Charger is the perfect blend of technology and practicality for all your power needs.

Required Material

1. Silicon wire
2. Crocodile Clips
3. 12-0-12 Transformer

Tools

1. TS80P Soldering Iron
2. MHP30 Preheater
3. Soldering Wire
4. Helping Hands
5. Screwdriver
6. Multimeter

Check BOM File for SMD & Through Hole Components also with designator.

Getting Started with design the simple circuit diagram in altuim 365 & converted it's Gerber file. 12V Hyper Battery Charger circuit efficiently regulates and controls the charging process while ensuring protection for the battery. It starts by converting AC power into DC using a GBJ1506 bridge rectifier, which is then smoothed by capacitors to provide a stable voltage. The LM317 voltage regulator, in combination with an MJD2955 power transistor, manages the output voltage and current.

To adjust the charging parameters, the circuit uses two potentiometers—one for voltage control and another for setting the current threshold. A relay plays a key role in switching the charging process, activated by a BC547 transistor when the battery needs to be charged. As the battery voltage increases, a sensing mechanism deactivates the relay to prevent overcharging. A buzzer and indicator LEDs signal the charging and full charge states, ensuring clear user feedback.

Additional safety features include diodes (1N4007) to prevent reverse polarity, and resistors for biasing and current control. The inclusion of a reset switch allows manual intervention when needed. Altogether, this circuit provides a reliable and intelligent way to charge a 12V battery while protecting it from overcharging and excessive current flow.

Below you can find the schematic that I followed when making all the connections.

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It's very important to first clean the PCB with some isopropyl alcohol. Then apply solder paste on the pads by using a solder paste syringe. It's a very good choice if you're using stencil to do this work. Place parts with tweezers making sure that resistor, diode, etc. are properly aligned. I like having a second board with no paste on it to see the alignment dots.

Now you have many options to cook the PCB like a hot air soldering gun, Hot plate, reflow oven, etc. I have used my Miniware MH30 hot plate to solder the PCB. Set the temperature according to your solder paste melting point and place the PCB on the hot plate.

It is important to look at the reflow profiles of all your components, to see how long you can heat your components for, and at what temperature. I usually just "wing it", and heat them at about 250C, for about a minute. You will see the solder melting, and the components being soldered into their respective places. Now you can turn off the hot plate and let it cool down completely.

The PCB has some through-hole components like- Capacitor, Bridge Rectifier, Screw Terminal and Relay.

First place all the components to it's place and mask it using masking tape. Now tun the first leg of all components for balance and then solder it one by one. To do this Soldering process, I'm using my Miniware TS80P Soldering Iron.

Once you have completed the soldering process it is important to remove the flux from PCB. Spray a small quantity of IPA (Isopropyl alcohol) Solution and clean it with cotton. Now the PCB boards are ready to use.

The transformer has three wire, Red-Blue-Red which stands for 12-0-12. Simply connect these three wire to PCB input Screw Terminal by using a screwdriver. PCB has already marked three polarity 12-0-12 for easy connection.

To create the charging clip, attach crocodile clips to silicone wires, ensuring a strong and secure connection. Use a red wire for positive (+) and a black wire for negative (-) to avoid confusion.

Once the clip is ready, connect it to the PCB’s output screw terminal using a screwdriver. The PCB is already marked with + (positive) and - (negative) signs. Securely connect the black wire to the minus (-) terminal and the red wire to the plus (+) terminal to ensure proper polarity.

To ensure proper charging, you need to calibrate the circuit by setting the charging voltage and auto cut-off voltage.

1. The first potentiometer controls the charging voltage. Slowly rotate it clockwise to increase the voltage and counterclockwise to decrease it. Adjust it according to your battery's required charging voltage.
2. The second potentiometer sets the auto cut-off voltage. Turn it slowly clockwise until the green LED turns on, indicating that the cut-off point is set. This ensures the charger stops supplying power once the battery is fully charged, preventing overcharging

With proper calibration, this smart charger will efficiently and safely charge your battery.

Before testing, ensure all connections are secure. Connect the transformer's AC input wires to a 220V power source, ensuring proper insulation for safety. Attach the charging clips to the battery, checking the polarity, red to positive (+) and black to negative (-) to avoid damage.

When charging begins, the red LED will glow. Avoid touching exposed wires during this process. Once fully charged, the green LED will light up, and the buzzer will sound, indicating completion. If the charger needs to be restarted or a fault occurs, simply press the reset button to restore normal operation.

Never leave the charger unattended. Use insulated tools, keep it away from water, and avoid charging damaged batteries. After charging, disconnect the power to ensure safety and longevity.

In my conclusion, this project aimed to design overcharge protection, status indicators, and a buzzer alert, ensuring safe and efficient battery charging.

However, during testing, several issues were identified, including incorrect voltage regulation, potential relay switching failures, and improper charge detection. To make the circuit fully functional, it is essential to verify component connections, ensure correct resistor values, and check the relay and transistor switching mechanisms.

With proper debugging and minor corrections, this circuit has the potential to become a reliable and safe 12V battery charger, suitable for various battery types while preventing overcharging and excessive current draw.