Like many, I'm getting pretty poor battery life from my iPhone 4, so I've been looking at a simple replacement to see if this improves anything. Being loathe to pay the £100/$100 charged for the "full service", I've been looking at doing it myself. Having seen what's involved, I am happy that I can do the job but I do have some questions : 1. Supposedly genuine Apple replacement batteries retail around the £9 mark - how can I tell if it's "OEM"? 2. Like for like replacements retail for roughly half that price - what do I need to look out for here? Surely Apple simply buy their batteries in from a trusted and probably well known supplier? 3. My main concern of course is whether the cheaper replacements could "fry" or otherwise damage the phone. Does anyone have any experience of this? 4. The final question is about so called "high capacity gold" replacement batteries. The OEM iPhone 4 battery is apparently rated at around 1,240mAh whereas these claim up to 2,450mAh, ie almost double. These retail for little more than the OEM replacements. Does anyone have any experience about the effectiveness and reliability of these?