Design a circuit to recharge a battery

In summary, a circuit design is needed to recharge a 1.2-V Ni-Cd battery from a 12-V car battery with a current of approximately 10 mA. The solution involves using a resistor of 1.1 k-Ohms in a loop equation, knowing that modern car batteries are generally 12V and adding voltage regulation for a constant voltage in the charging circuit.
  • #1
VitaX
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Homework Statement



Design a circuit to recharge a 1.2-V Ni-Cd battery from a car battery with a current of approximately 10 mA.

Homework Equations





The Attempt at a Solution



I was looking in the back of the book on this one and it had a simple circuit devised with a 12-V battery and 1.2-V battery and a resistor of 1.1 k-Ohms. I know a loop equation is needed here, but shouldn't there be at least one more known in the problem? I don't understand how to find the voltage of the car battery as well as the resistance of the resistor, but if the voltage of the car battery is known, it becomes pretty simple to find the resistance of the resistor within the circuit. How should I go about approaching this problem?
 
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  • #2
Modern car batteries are generally taken to be 12V. There was a time when 6V batteries were common, too, and even today some trucks have 24V batteries. But today it's almost always 12V for a car battery.

Note that a car battery in a running car is being recharged by the alternator, and as a result can read something like 13.7V or so. But you shouldn't have to worry about this here -- no mention was made of a car in the problem, just the car battery.

If bonus points were available, you might add some voltage regulation after the car battery to ensure a constant voltage for the charging circuit :smile:
 
  • #3
gneill said:
Modern car batteries are generally taken to be 12V. There was a time when 6V batteries were common, too, and even today some trucks have 24V batteries. But today it's almost always 12V for a car battery.

Note that a car battery in a running car is being recharged by the alternator, and as a result can read something like 13.7V or so. But you shouldn't have to worry about this here -- no mention was made of a car in the problem, just the car battery.

If bonus points were available, you might add some voltage regulation after the car battery to ensure a constant voltage for the charging circuit :smile:

Wow I feel dumb now. I get 1080 Ohms, while the book gets 1.1 k-Ohms, guess they rounded but easy problem. Thanks for that.
 

1. How do I design a circuit to recharge a battery?

To design a circuit to recharge a battery, you will need to consider the voltage and current requirements of the battery, as well as the type of battery you are using. You will also need to choose a suitable charging method, such as constant current or constant voltage charging, and select appropriate components for your circuit.

2. What is the difference between constant current and constant voltage charging?

Constant current charging involves supplying a steady current to the battery until it reaches a certain voltage. This method is commonly used for charging lithium-ion batteries. Constant voltage charging, on the other hand, involves supplying a constant voltage to the battery until the current drops to a certain level. This method is often used for lead-acid batteries.

3. Can I use any type of battery in my circuit?

No, you should always use a battery that is compatible with your circuit's voltage and current requirements. Using the wrong type of battery can damage your circuit or cause it to malfunction. It is important to carefully read the specifications of your battery and choose a compatible charging method.

4. How can I ensure the safety of my circuit when charging a battery?

Safety should always be a top priority when designing a circuit to recharge a battery. To ensure safety, you should use appropriate components, such as fuses and voltage regulators, to protect your circuit from overcharging or short-circuiting. It is also important to follow proper charging procedures and never leave your circuit unattended while charging.

5. Are there any additional considerations for designing a circuit to recharge a battery?

In addition to voltage and current requirements, you should also consider the temperature range of your battery and choose components that can withstand the temperature conditions. It is also important to consider the charging time and efficiency of your circuit, as well as any potential environmental impacts of your chosen battery and charging method.

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