Nickel Metal Hydride (Ni-MH) batteries are really popular for portable electronic devices because they have a great energy density and can be recharged.
To make sure these batteries last a long time and work well, it is super important to follow the right charging methods.
The circuit diagram shows a strong and effective charger made just for Ni-MH batteries using the LT4060 integrated circuit from Linear Technologies.
This special IC is designed to be a battery charger controller helping to charge 1.2V Ni-MH batteries efficiently.
In this article, you will find a detailed look at the Ni-MH battery charger circuit that uses the LT4060 including how it works, important formulas, building tips and final thoughts.
Circuit Working:
Parts List:
| Component | Value/Specification | Quantity |
|---|---|---|
| Resistors | 330Ω, 698Ω | 1 each |
| Preset 10k | 1 | |
| NTC Thermistor | 10k | 1 |
| Capacitors | Ceramic 1.5nF | 1 |
| Semiconductors | IC LT4060 | 1 |
| Transistor 2N2907 | 1 | |
| Battery | Ni-MH in series 1.2V | 2 |
The circuit uses a 5V DC power supply that connects to the Vcc pin of the LT4060 chip.
This chip controls the charging current through the DRIVE pin, which helps manage how the Q1 2N2907 transistor works.
The amount of charging current depends on the resistance of resistors R3 and R4.
There is also an NTC thermistor R2 that keeps an eye on the batteries temperature.
If the temperature gets too high the chip will stop charging to protect the battery from damage.
The IC LT4060 has a smart charging system that starts by sending a constant current to the battery until it reaches a certain voltage.
Once the battery is fully charged the chip switches to a trickle charge mode to keep the battery charged. Additionally, the timer capacitor C1 helps set the maximum charging time to avoid overcharging.
The exact time is figured out using a specific formulas mentioned below.
Formulas and Calculations:
The formulas with calculations for Simple Ni-MH Battery Charger Circuit is mentioned below:
Charging Current (Icharge):
The charging current is set by resistor R3 and R4:
Icharge = 1000 / R3 and R4 (in Amperes)
For R3 and R4 = 680Ω +18Ω
Icharge = 1000 / 698 = 1.43 mA
Timer Duration (Tcharge):
The charging time is determined by the capacitor C1 and follows the formula:
Tcharge = 3 × C1 × 10^6 (in seconds)
For C1 = 1.5 nF:
Tcharge = 3 × 1.5 × 10^(-9) × 10^6 = 4.5 seconds
Battery Voltage (Vbattery):
The Ni-MH battery pack voltage is calculated as:
Vbattery = N × Vcell
where,
N = 2 (number of cells) and Vcell = 1.2 V
Vbattery = 2 × 1.2 = 2.4 V
How to Build:
To build a Simple Ni-MH Battery Charger Circuit following steps must be followed for building and connections:
- Gather all the components mentioned in the above circuit diagram.
- Connect DRIVE pin 1 of IC1 LTC4060 to the base of transistor Q1, connect collector of Q1 transistor to BATTERY pin 2, and connect emitter of transistor Q1 to SENSE pin 3 of IC1.
- Connect pin 4 TIMER to one end of capacitor C1 and connect other end of capacitor C1 to GND.
- Connect pin 5 SHDN, pin 8 ARCT, and pin 9 SELO of IC1 to +5V DC.
- Connect pin 6 PAUSE, pin 10 SEL1, pin 12 CHEM of IC1 to GND
- Connect pin 7 PROG of IC1 to resistors R3 and R4 in series and GND.
- Connect pin 11 NTC of IC1 between one leg of VR1 preset and the other leg of VR1 to+5V DC and R2 NTC and other end to GND.
- Pin 13 ACP of IC1 is N/C pin.
- Connect pin 14 VCC of IC1 to +5V DC
- Connect pin 15 CHRG of IC1 to negative of LED1 and positive of LED1 to one end of resistor R1 and connect other end of resistor R1 to +5V DC
- Connect pin 16 GND of IC1 to GND of the circuit.
Conclusion:
The Simple Ni-MH Battery Charger Circuit is a dependable and effective way to charge Ni-MH batteries.
It comes with safety features like temperature checks and a timer to help keep the battery pack safe and lasting longer.
This charger is great for different uses that need rechargeable Ni-MH batteries including portable gadgets, toys and backup power supplies.
If you put it together correctly and follow the guidelines, you will have a strong and efficient charging system.