Pro Charger delivers high-performance charging & 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 & visual alerts. A red light means that charging has started, & you will hear an audible beep when charging begins. A yellow light appears when charging is 50 percent complete & charging is continuing. A green light means charging is complete, & 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, & 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.