Pro Charger delivers high-performance charging and great savings over disposable batteries. Paired with long-lasting Energizer Recharge batteries you can charge two or four AA or AAA batteries in just 3 hours. The charger is equipped with audio and visual alerts. A red light means that charging has started and you will hear an audible beep when charging begins. A yellow light appears when charging is 50 percent complete and charging is continuing. A green light means charging is complete and the batteries are 100 percent full. You will hear an audible beep upon completion. If a bad battery is detected a red X will illuminate and the charger generates a repetitive audible beep upon detection. The Pro Charger charges two or four AA/AAA NiMH rechargeable batteries in three hours or less.