When the float voltage is reached and the charging current drops to 1/10 of the defined circuit, the LTH7R IC automatically completes the charging process.

Features

• Programmable charging current up to 500mA
• No need for external MOSFET, sensing resistor, reverse diode
• Constant current or constant voltage mode operation, with thermal protection function Preset charging voltage
• Standby current is 20uA
• 2.9V slow charge voltage
• Soft start limits the inrush current
• Adopt SOT23-5 package, application line
  
  

Product application

• Microphone Battery
• Light Camera
• Mobile Phones, PDAs, MP3 players
• Bluetooth headsets 

External programming of the load current:

PROG (pin 5): Constant current load current setting and load current monitoring terminal. The load current can be programmed by connecting an external resistor from the PROG pin to ground.

In the pre-charge phase, the voltage of this pin is modulated by 0.1V; in the constant current charging stage, the voltage of this pin is fixed at 1V.

In all charging state modes, measuring the voltage of this pin can estimate the charging current according to the following formula:

General Formula:

I_bat = 1000 / R_prog

To use, for example, in a charger whose required current is 300mA, we can use the formula as follows:

• I_bat = 1000/ R_prog
• R_prog = 1000 / I_bat
• R_prog = 1000 / 300
• R_Prog = 3.3K

To use, for example, in a charger whose current required is the maximum current, 500mA, we can use the formula as follows:

• I_bat = 1000/ R_prog
• R_prog = 1000 / I_bat
• R_prog = 1000 / 500
• R_Prog = 2K
  
  

We leave just below a small table ready with five models with the standard currents for the battery charger.

Model	R_prog	I_bat
1	10K	100mA
2	5K	200mA
3	3,3K	300mA
4	2,5K	400mA
5	2K	500mA

The Circuit Schematic

In Figure 2, below, we can see the schematic diagram of the Automatic Programmable 4.2V Battery Charge, Current up to 500mA using LTH7R IC.

All circuit components are SMD, the power supply input is done by soldering on the PCB. This type of miniaturized SMD circuit is great to be implemented in circuits with small spaces.

The capacitors are SMD electrolytic, but if you have tantalum capacitors, you can put them on, it will help with the plate height, but if you can't find them, you can use electrolytic.

The charger circuit supports voltage between 4.4V to 7V, the recommended is 5V, which is great news for us to be able to charge our battery in a PC USB port or even with cell phone chargers.

Fig. 3 - Automatic Programmable 4.2V Battery Charge, Current up to 500mA using TH7R 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. 4 - PCB Automatic Programmable 4.2V Battery Charge, Current up to 500mA using TH7R 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.

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My Best Regards!!!

• 3.7V Li-Ion Battery Charger Circuit using MCP73831 IC + PCB
• Simple 12V battery charger with automatic charging indicator + PCB
• Lithium (Li-Ion) Battery Charger using LP2951 IC + PCB
• 12 Volts Automatic Lead Acid Battery Charger Using LM350 IC with PCB
• USB 5V 4A Car Charger using 78S05 with PCB
  
  

The Power Transformer

The transformer should have as primary according to your local network, 110Vac or 220Vac. The secondary should be 12V, since when we pass through the rectification, this 12Vac voltage is transformed more or less into 16.9Vdc.

The transformer should have a current of 3 amps, in case you are going to use it with large batteries, such as 7A, 9A, etc… 

If you are going to work with smaller batteries, it is up to you to place a transformer proportional to the total power of the LEDs and the battery used. The transformer configuration diagram is shown in Figure 4 below.

Fig. 3 - Schematic Diagram Transformer 110/220Vac to 12Vac 3Amps

Component List

Fig. 4 - PCB - Rechargeable Emergency LED Light Using LM350 IC

Click on the direct link to download the files: Layout PCB, PDF, GERBER, JPG

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

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Fig. 1 - USB 5V 4A Car Charger using 78S05

L78S00 Description

Feature

• Output Current to 2A.
• Output  Voltage of: 5 ; 7.5 ; 9 ; 10 ; 12 ; 15 ;18 ; 24V.
• Thermal Overload Protection.
• Short Circuit Protection.
• Output Transistor SOA Protection
  
  

Circuit Operation

In Figure 2, below, we can see the schematic diagram of USB 5V 4A Car Charger using 78S05, the Circuit's operation is pretty basic, what happens is that when you plug your USB converter into the cigarette socket of your car, it converts this 12V battery voltage to a regulated 5V voltage.

Fig. 2 - Schematic circuit USB 5V 4A Car Charger using 78S05

The total output current of the circuit is 4 Amps, 2A for each USB port, this is enough current to charge any USB device today.

The circuit has overload protection, which means that if there is a short circuit on the output, or if a device with higher current is connected to the USB converter, it will shut down, until that current is reduced to a maximum of 2A.

Components List

• Semiconductors
• U1, U2 ...... 78S05 Integrated Circuit Voltage regulator
• LED1 ....  Light Emitter Diodo, general purpose
  
  
• Resistor
• R1 ..... 4.7KΩ (yellow, violet, orange, gold) 
• RP1 ......... 10KΩ Trimpot

• Capacitor
• C1 .......... 47nF Ceramic Capacitor
• C2 .......... 100nF Ceramic Capacitor
• C3 .......... 4.700uF / 35V Electrolytic Capacitor 
  
  
• Miscellaneous 
• F1 .......... 20A - 250V soldering Fuse
• P1 .......... 2-pin PCB soldering terminal blocks
• P2 .......... 3-pin PCB soldering terminal blocks
• Others .... Printed Circuit Board, heat sink, 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 - USB 5V 4A Car Charger using 78S05

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.

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My Best Regards!!!

You may be interested in: 

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

Working

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

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!!!

LP2951 Integrated Circuit

Features

• Low Quiescent Current 
• Low Dropout Voltage
• Low Temperature Coefficient
• Tight Line and Load Regulation
• Guaranteed 100mA Output Current
• Internal Short Current & Thermal Limit
• Error Signals of Output Dropout (8 pin Versions only)
• External Shut Down ( 8-Pin Versions Only)
  
  

The Circuit

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

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

Capacitor C1 and C2 act as an RF filter to eliminate spurious, capacitor C3 is for stability of the feedback system, the 50K potentiometer RP1 is to adjust the system according to the operating voltage of the cell.

The Li-Ion battery charger circuit can be powered by a DC voltage between 6 to 10V with a current equal to 1.5 times the capacity of the cells to be charged.

Charger Operation

When we connect the power supply to the circuit and insert the battery, the LP2951 IC checks the charging status and, when it detects a charge below the programmed one, it triggers the charging to complete the charge.

After the battery is fully charged, the circuit goes into sleep mode, it keeps checking periodically the status of the battery and if necessary it activates the continuity of charging. 

Components List

• Semiconductors
• U1 .......... LP2951 Voltage Regulator Circuit
• D1 .......... 1N4007 Silico Diode
  
  
• Resistor
• R1 .......... 2MΩ 1%  Precision Resistor (red, black, yellow, brown)
• R2 .......... 806KΩ 1%  Resistor (gray, black, blue, orange, brown) 
• RP1 ........ 50KΩ Potentiometer
  
  
• Capacitor
• C1 .......... 0.1uF or 100nF Polyester/Ceramic Capacitor
• C2 .......... 2.2uF / 16V Electrolytic Capacitor
• C3 .......... 470pF Polyester/Ceramic Capacitor
   
  
• Other
• B1, B2 ... 2-pin PCB soldering terminal blocks
• Others .... Printed Circuit Board, 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 - Lithium (Li-Ion) Battery Charger using LP2951 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!!!

This is a Smart Battery Charger, with fully automatic 12V battery charge indicator. It is an extremely simple charger that anyone with little experience can assemble.

The input voltage depends on the power supply you are using, 110Vac or 220Vac. The charging time depends on the power supply you are using and the type of battery you are charging.

To calculate the closest charging time, we can do a simple and objective quick calculation that does not take into account the variations of the resistance factors of the battery, the variations of the charger, the chemical depreciation factor of the battery and so on.

You may be interested in: 

The calculation is quite simple. Let us take an example: you have a UPS 12 volt battery with 7 amps, your power supply is 3 amps. 

So we know that the battery charge is "more or less" 7 Amps Hour, which means that to fully charge the battery, 7 constant amps are required. Since the power supply is 3 amps, we need to divide 7 amps by 3 amps of power supply.

To charge a battery without damaging it usually requires a current of 10% and a maximum of 20% of its current. For example:

If our battery is 7 amps, the most we need is a 1.4 amp charger, and normal charging consumption is 700 milliamps. This 10% is normally used in devices that are directly connected to the power, such as alarm systems, backup devices and others.

Let's do the calculations using the formula

• B = battery
• PS = power supply
• C = current

C = B / PS

C = 7/3 C = 2.33

Meaning:

Charge "C" lasts 2:33 hours

Two hours and thirty-three minutes to charge

If your PS is different, no problem, look at its supply current and put in the formula to see the approximate result.

Figure 2 shows the complete electrical schematic of the small circuit.

Fig. 2 - Electronic Schematic Simple 12V Automatic Battery Charger

It is important that the power supply delivers 20% more than the battery voltage, e.g. if your battery is 12 V, the power supply must be 14,4 V. You can vary a little, e.g. 13.2 V, "which is 10% of the battery voltage", but you cannot use a 12 V power supply to charge a 12 V battery as there will be no potential difference.

Here is how to use the charger:

When all the assembly is done, carefully check for wrong parts, reverse polarity diodes and shorts in the terminals after checking everything.

Connect the positive terminal of the power supply to the input of the +Vcc circuit and the negative terminal of the power supply to the ground circuit of the charger. 

With the potentiometer or trimpot you can regulate the output voltage of the charger, for example you have a 12V battery, normally 12V batteries UPS are charged at 13.2V at 14.4 volts.

Then use a multimeter on the DC volt scale, "it depends on the multimeter", on the output of the charger and set the voltage to the most desired, ie the maximum voltage for it to fire and the green LED will light up.

You can now use your new charger, insert the battery and let it charge until the charger reaches the voltage you set, "limit voltage", it will trigger the relay and turn on the green LED, indicating that the battery has been charged.

A good tip: If you have a spare 12v buzzer, or if you really want to add an audible indicator to your circuit, you can connect these buzzers, which you can easily find in electronics stores and are cheap, to the output where the green LED is lit, which is the full charge indicator, and you can turn on the positive buzzer on the relay output and the negative buzzer directly on the output.

Material List:

• Q1..................... General purpose NPN transistor, C1815, BC548 etc.
• D1, D2, D3 ...... Diodes 1N4001.
• R1 ..................... Resistor 1/8W 10K (Brown, Black, Orange)
• R2 ..................... Resistor 1/8W 100 Ohms (Brown, Black, Brown)
• R3 ..................... Resistor 1/8W 1K2 (Brown, Red, Red)
• VR1 ................. 10K Trimmpot or Potentiometer
• P1, P2 ............... KF301 2 Pin 5.08mm Pitch Plug-in Screw Terminal Block Connector 
• RL1 ................... Relay 12V 10A, 5 pins
• LED1, LED2 .... 3mm LEDs, one Red and one Green
• Others ............... Printed circuit board, soldering iron, tin, wire, etc.

Fig. 2 - 3.7V Li-Ion Battery Charger Circuit with IC MCP73831

Features

Components List

The PCB - Printed Circuit Board

Files to download, Direct Link: