Automatic nimh battery charger circuit

A nickel-metal hydride battery, also known as NiMH, is a secondary cell.They are used in cameras and other electronic devices. They are widely used Because it’s cheap and has a flow rate capacity of the cells to be used as required. Can replace the generic battery immediately.

Important. Can bring to new charging hundreds to thousands of times. Make savings in the long run. and also help maintain the the environment.

Though we will generally choose to buy battery charger. Which is both fast and slow charging. Based on the budget, there, which is most expensive. We should build it up by yourself, because it’s cheap and good quality.

The project is the NiMH battery charger circuit on automatically shut off when fully charged. Can charge the batteries from 1-10 pcs. Depending on the input voltage.

In circuit has LED indicator are 2 LEDs. By showing the charging status and will be off when the battery is fully charged.
And the LED function indicator that the battery is connected correctly.

For input voltage is supplied to the charger circuit can be used for the power supply ranging from 12-16 volts and use current to charge to 800 milliamperes.

Operation of the circuit.

From the circuit in Figure 1. When connects the battery into both point P3 and P4. There is LED2 will glow In the event of connecting correctly of all battery. If battery reverse polarity, this LED2 go out, We need to check the battery correctly.

Some voltage from the battery is compared to the voltage at IC1-TL072. Which the TL072 is determined to compare the voltage between pin 2 and pin 3.

NI-mh-battery-charger-circuit-using TL072
Figure 1 Automatic ni-mh battery charger using TL072

In case the voltage from battery to charge each cell is still low. The output from pin 1 of IC1-TL072 will send to a transistor Q1, Which acts as switch on-off working to transistor-Q2 so the current can flow to the battery.
And when the circuit is charging there LED1 will show the charging status.

When the battery is full, its the voltage is compared at the IC1, will make an output at pin 1 of IC1 go to stop working of Q1-transistor, then also causes the Q2-transistor stop.

The end of battery charging, and LED1 indicator charging is off, to display that the battery is full enough.

The Amount of current in charging battery of the project is determined at 800mA. By there is R7-resistor is a current limiter as above.

The S1-switch is pushed for starting charging, in the event that the battery correctly. But not available charging so we can push it to recharging again. To test that this battery has Fully charged.

How to builds this project.

This project have a few components so easy to build. First make the single-sided PCB layout as Figure 2 or can also use easily the Universal PCB Board. Then assemble all parts on the PCB as Figure 3 Which We recommend detailed only because they think you can create your own.

Figure 2 The single-sided PCB layout of Automatic ni-mh battery charger.

Figure 3 The Component layout for the PCB.

The Detail Components
Q1______BC327__ 50V 800mA PNP Transistor ___________= 1 pcs.
Q2__________MJE2955___50V 3A PNP Transistor_________= 1 pcs
D1,D4______1N4148_____75V 150mA Diodes____________ = 2 pcs.
D2,D3______1N4001_____50V 1A Diodes_______________ = 2 pcs.
Electrolytic capacitors
C1,C4______1000uF 25V Electrolytic capacitors___________ = 2 pcs.
C5_____1uF 50V Electrolytic capacitors__________________= 1 pcs.
C2,C3______0.1uF 100uF polyester capacitors_____________ = 2 pcs.
1/4 watts 1% Resistors
R1_________10K_______________= 1 pcs.
R2_________1M_______________= 1 pcs.
R3,R9_______1K_______________= 1 pcs.
R4_________ 470 ohms__________= 1 pcs.
R5_________ 150 ohms 2 watts____= 1 pcs.
R6, R8______100K______________ = 2 pcs.
R7___________1 ohms 2 watts_____= 1 pcs.

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