There are several signs that your car battery may need to be replaced, including slow cranking, dim headlights, and a dead battery. If the engine takes longer than usual to start, or the headlights appear dimmer than usual, this may indicate that the battery is losing its charge or capacity. A dead battery, which can occur if the battery is drained or damaged, may also require replacement. If you suspect that your battery needs to be replaced, it is important to have it tested by a professional to ensure that it is functioning properly.