Bests & Worsts Reviews from Amazon

If you're wondering how it is possible to cram more juice into the same sized battery as stock, that's because this is using a different technology- Lithium Polymer as opposed to Lithium Ion. The Polymer batteries can chemically store slightly more energy in the same size cell, resulting in this boost of power. Don't be fooled- there are plenty of "fake" extended batteries that just have a capacity printed on a sticker in China but don't actually offer any additional battery life. This one, however, is the real deal. Accubattery is reporting somewhere around 4085 mAh capacity in the battery health section, which means this pack is within 99% of the rated capacity. My original OEM v20 battery's health has depreciated to around 2800mAh and can barely make it to dinner time without a recharge. This Perfine 4100 now gets me enough juice to last the entire day with some left over when I go to bed at night! Generally I end the day with about 3.5-4 hours of screen on time and 20-30% left on the battery, and plug it in around midnight. On days that I use it extensively (5+ hours of screen time) I might need to top it off in the car on my commute to last until bed time, but that honestly hasn't happened yet. The battery is THAT good! I particularly like that I can use factory sized cases with this battery so that I can use it in a wallet style holder. NOTE: The first one I got was a tight fit. The back didn't really want to stay on, but I saw some people recommend carefully removing the sticker from the back and lo and behold, that's all it took to be svelte enough to fit in the stock back! I received a second one and this one actually managed to fit without removing the sticker so apparently there's some sample variety in manufacturing or something like that. Luck of the draw, you might get one that fits without doing anything or you might need to peel off the label sticker to make it fit.