90% of the batteries in the pack are defective. I replaced the batteries in my toothbrush tonight which is only 2 months old (new batteries when I first used it). The replacement batteries did not work. Finally resorted to opening a pack of energizers and they work like a champ. This is not the first time that these batteries did not work. Air fresheners, wireless mice, the kids remote controls. the list goes on and on. I feel like I have thrown my money away!