1. The problem statement, all variables and given/known data An automobile battery when connected to a car radio provides 12.5 V to the radio. When connected to the headlights, it provides 11.7 V. Assume the radio is modeled as 6.25 ohm resistor and the headlights are .65 ohms. Find the Thevenin Equivalent for the battery. 2. Relevant equations V=IR 3. The attempt at a solution The battery is modeled as an ideal voltage source, Vth, with an internal resistance of Rth, and the Rl is either the radio or headlights are the load across the terminals. I looked at the loop equations Vth-RthI-RLI=0 for both resistors, then tried to solve both simultaneously. I'm thinking my setup isn't reflecting the problem. Does the battery voltage matter? It seemed to cancel out. Help?