There are several features related to the charging process of various battery segments and classes. 
The charging method for lead-acid batteries differs from NiCd batteries in the voltage limit, rather than the current limit to be used.

The charging time for lead-acid (sealed) batteries is 8 to 16 hours, depending on the capacity of the battery and the method used. 

With higher charging currents and multi-stage charging methods, the charging time can be reduced to 8 hours or less. 

For a multi-stage charger, three stages of charging application are required: 

The Circuit

In Figure 2 below, we have the schematic diagram of the lead-acid battery charger circuit. It is a very simple circuit, with few external components, easy to assemble, yet even with its simplicity it works very well.

Fig. 2 - Schematic Circuit 12 Volts Automatic Lead Acid Battery Charger Circuit

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How it Works?

The voltage regulation for charging the battery is done by the LM350 IC voltage regulator. The charging current control is done using the BC548B NPN transistor, it controls the demand current from the battery, causing the circuit to activate or deactivate the voltage required for charging the battery.

The potentiometer RP1 1K is used for fine tuning the battery charging voltage, which should be adjusted by using a multimeter to measure the output voltage, which should be at most 20% of the nominal battery voltage.

If you cannot find the description of the battery charging voltage on the battery itself, you can adjust the average charging voltage, which ranges from 13.8V to 14.4V.
It is necessary to use a heat sink in the voltage regulator, since the initial current to charge the battery is high. 

As the circuit charges the battery, it lowers the charging current until it reaches zero voltage, when the battery is fully charged.

Components List

• Semiconductors
• U1 .......... LM350 Voltage Regulator Circuit
• Q1 .......... BC548B NPN Transistor
• D1 .......... 1N5408 Silico Diode
  
  
• Resistor
• R1 .......... 100Ω Resistor (brown, black, brown, gold)
• R2 .......... 0.5Ω 5W Resistor (green, black, silver, gold) 
• R3 .......... 470Ω Resistor (yellow, violet, brown, gold)
• R4 .......... 120Ω Resistor (brown, red, brown, gold)
• RP1 ........ 1KΩ Potentiometer
  
  
• Capacitor
• C1 .......... 2.2uF / 25V Electrolytic Capacitor
• C2 .......... 0.33uF / 25V Electrolytic Capacitor
   
• Other
• P1, P2 .... 2-pin PCB soldering terminal blocks
• Others .... Printed Circuit Board, Heat Sink, tin, wires, etc.

Printed Circuit Board

In Figure 3, we provide the PCB - Printed Circuit Board, in GERBER, PDF and PNG files. These files are available for free download, on the MEGA server, in a direct link, without any bypass. 

All to make it easier for you to do a more optimized assembly, either at home, or with a company that prints the board. You can download the files in the Download option below.

Fig. 3 - PCB - 12 Volts Automatic Lead Acid Battery Charger Circuit

Files to Download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files

🌐 You can read this article in: Português | Español

In today's post, we will build a lithium-ion (Li-Ion) battery charger. The circuit performs controlled charging, which represents a longer lifespan for your battery and a full charge giving more autonomy to the batteries.

All of this in a simple way, as the external components are minimal, due to the IC having integrated in its package all the necessary components to perform the task.

🔬 Additional Features

The LP2951 has three additional features. The first is the Error Output that can be used to signal external circuits of an out-of-regulation condition or as a microprocessor reset activator. 

The second feature allows the output voltage to be preset to 5.0 V, 3.3 V or 3.0 V (depending on the version) or programmed from 1.25 V to 29 V. It consists of a fixed resistor divider along with direct access to the Error Input in the internal operational amplifier feedback. 

The third feature is a shutdown input that allows a logic level signal to turn off or on the regulator output.

Due to the low input-to-output voltage dropout specifications and bias current, this device is ideal for battery-powered computers, consumer and industrial equipment where battery life extension is desirable.

The LP2951 is available in eight-pin surface mount packages, SOIC-8 and Micro8. Devices with the 'A' suffix feature an initial output voltage tolerance of ± 0.5%.

#️⃣ Features

• Available in Pb-Free package

• Low quiescent bias current 75 uA

• Low input-to-output voltage dropout of 50 mV at 100 uA and 380 mV at 100 mA

• Output of 5.0 V, 3.3 V or 3.0 V ± 0.5% allows use as regulator or reference

• Extremely tight line and load regulation

• Requires only a 1.0 uF output capacitor for stability

• Internal current and thermal limit

• NCV prefix for automotive and other applications requiring site and control changes

• Error output signals an out-of-regulation condition

• Programmable output from 1.25 V to 29 V

• Logic level shutdown input

🔌Schematic Diagram of the Charger Circuit

In Figure 2 below we can see the schematic diagram of the Li-Ion battery charger, and the LP2951 IC is responsible for measuring the battery status through the voltage divider at the battery charging voltage output, and with this, control it to not emit unnecessary charge.

Fig. 2 - Schematic Diagram Lithium (Li-Ion) Battery Charger using LP2951 IC

• Very high output power, operating from a single low supply voltage
• Low power dissipation, when used for music signals
• Switches to low output power at too high case temperatures
• Few external components
• Fixed gain
• Differential inputs with high common mode rejection
• Mode select pin (on, mute and standby)
• Status I/O pin (class-H, class-B and fast mute)
• All switching levels with hysteresis
• Diagnostic pin with information about:–  Dynamic Distortion Detector (DDD)–  Any short-circuit at outputs–  Open load detector–  Temperature protection.
• No switch-on or switch-off plops
  
  

The Schematic

Fig. 2 - Schematic 14.4V, 70W High Efficiency Power Amplifier using TDA1562Q IC

Printed Circuit Board

In Figure 3, we provide the PCB - Printed Circuit Board, in GERBER, PDF and PNG files. These files are available for free download, on the MEGA server, in a direct link, without any bypass. 

All to make it easier for you to do a more optimized assembly, either at home, or with a company that prints the board. You can download the files in the Download option below.

Fig. 3 -  PCB 14.4V, 70W High Efficiency Power Amplifier using TDA1562Q IC

Files to Download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files

If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

Subscribe to our blog!!! Click Here - elcircuits.com!!!

My Best Regards!!!

🌐 You can read this article in: Português | Español

💡 Expert Tip: This project is ideal for anyone seeking a high-power amplifier with excellent sound quality for home audio systems, small events, or home recording studios.

🎯 Main advantages of this project:

• High power with relatively simple components
• Excellent sound quality with low distortion
• Integrated thermal and short-circuit protection
• Compact design ideal for space-limited applications

🔍 For the curious: What makes the TDA7294 special?

The TDA7294 combines DMOS (double-diffused MOSFET) technology in the output stage with bipolar circuits in the input stages, resulting in a chip that offers the best of both worlds: the linearity of bipolar transistors and the efficiency of MOSFETs. That's why this IC is so valued in high-quality audio projects!

⚡ Analogy to understand the Bridge configuration:

Imagine two pushers on a seesaw. Instead of just one pushing (simple configuration), both push simultaneously in opposite directions, effectively doubling the applied force. That's exactly what the Bridge configuration does with the audio signal!

📊 Performance comparison:

⚠️ Important warning:

Never use speakers with impedance lower than 8Ω in this Bridge configuration! This can overload the TDA7294 ICs, causing overheating and possible permanent damage to the components.

🔍 Schematic analysis:

The schematic shows two TDA7294 ICs configured in bridge. The first IC (U1) functions as a non-inverting amplifier, while the second (U2) operates as an inverting amplifier. This configuration creates opposite audio signals that are applied to both ends of the speaker, effectively doubling the voltage across it and, consequently, quadrupling the power (P = V²/R).

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• Semiconductors
• U1, U2 ........................ TDA7294 Integrated Circuit
• D1 ............................... 1N4148 Silicon Diode
• Resistors
• R1, R5, R6, R8, R10 ... 22K Resistor (red, red, orange, gold)
• R2 ................................ 20K Resistor (red, black, orange, gold)
• R3 ................................ 10K Resistor (brown, black, orange, gold)
• R4 ................................ 30K Resistor (orange, black, orange, gold)
• R7, R9 ......................... 680Ω Resistor (blue, gray, black, gold)
• Capacitors
• C1, C4 ......................... 1μF Ceramic/Polyester Capacitor
• C2, C3, C5, C6 ............ 22μF Electrolytic Capacitor
• Others
• P1, P2 ......................... 5mm 2-Pin Screw Connector
• P3 ................................ 5mm 3-Pin Screw Connector
• J1 .................................3-Pin Male Connector Set (Optional)
• Other ........................... PCB, Wires, Speaker, etc.

💡 Assembly tips:

• Use good quality solder to ensure reliable connections
• Check the polarity of electrolytic capacitors before soldering
• Consider using sockets for the TDA7294 ICs to facilitate possible replacements
• Test the circuit with reduced voltage before applying full voltage

Version 1 - 150W Output.

• Speaker should be 8Ω and the maximum voltage is ±25V

Version 2 - 170W Output.

• Speaker should be 16Ω and the maximum voltage is ±35V.

🔧 Power supply recommendations:

To get the best performance from this amplifier, we recommend a power supply with good regulation and low ripple. Silicon steel core transformers and high-quality filter capacitors will make a noticeable difference in the final sound quality. Consider adding decoupling capacitors near the ICs to improve high-frequency response.

🔧 PCB manufacturing tips:

• For better heat dissipation, consider using a PCB with thick copper (35μm or more)
• If possible, add additional copper areas under the ICs to help with thermal dissipation
• Check if the power traces are wide enough to support the required current
• Consider adding mounting holes near the ICs to facilitate the installation of heat sinks

Click the link next to it: GERBER, PDF and PNG files

1. Can I use this amplifier with 4Ω speakers?

We don't recommend it. This Bridge configuration was designed to work with a minimum impedance of 8Ω. Using 4Ω speakers can overload the ICs, causing overheating and possible permanent damage.

2. Is it necessary to use heat sinks on the TDA7294 ICs?

Yes, absolutely! The TDA7294 ICs dissipate significant heat during operation, especially at high powers. We recommend using adequate heat sinks for each IC, with sufficient area to keep the temperature below 80°C.

3. Can I convert this amplifier into a stereo system?

To create a stereo system, you would need to build two circuits identical to this one, one for each channel. Alternatively, you could configure each TDA7294 individually (instead of in bridge) to create two lower power channels.

4. What is the expected sound quality of this amplifier?

The TDA7294 is known for its excellent sound quality, with low harmonic distortion (typically less than 0.1%) and low noise. You can expect a clean and detailed sound, suitable for high-fidelity audio applications.

5. Is this amplifier suitable for guitars or musical instruments?

Yes, this amplifier works very well for guitars and other musical instruments. Its high power and low distortion provide a clean and dynamic sound. For guitar applications, you may want to add a preamplifier circuit or effects before this power stage.

🎯 Tips to get the best performance:

• Use good quality wires for audio and power connections
• Position the ICs as close as possible to the decoupling capacitors
• Consider adding a fan to improve cooling during continuous use
• Use a Faraday cage or proper shielding if there is RF interference

You might also be interested in:

• 170W AB Class Bridge Mode Amplifier using TDA7294 IC + PCB
• 24W Stereo Hi-Fi Audio Amplifier using TDA2616 + PCB
• 68W Hi-Fi Audio Power Amplifier using LM3886T IC + PCB
• 4 x 50W High Power Amplifier, 14.4V - IC TDA7563A + PCB
• 320W Power Audio Amplifier, Powered with 14.4V - 2Ω with IC TDA7560 + PCB
• 100W RMS Audio Amplifier IC TDA7294 + PCB
• 200W RMS Stereo Power Amplifier with IC STK4231II + PCB
  
  

If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

Subscribe to our blog!!! Click Here - elcircuits.com!!!

My Best Regards!!!