1. The problem statement, all variables and given/known data Design a circuit to recharge a 1.2-V Ni-Cd battery from a car battery with a current of approximately 10 mA. 2. Relevant equations 3. 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?