I swapped my original battery with this one, expecting to get longer battery life. My phone kept crashing re-booting randomly, and I also discovered that my iPhone would not charge. To double-check I swapped back to my original battery and everything was working fine. So I am staying with my old battery as of this review. I could not tell if the battery is defective, or if there is an issue with compatibility with this battery and the iPhone 3GS based on my experience. Therefore I would not recommend this product to someone if they have an iPhone 3GS.