My Mugen 1800 mAH didn't work in my N810 until I added a shim made from card stock to the end of the battery. I don't know if this an issue with the battery size or perhaps where the batterry contacts are positioned. Also my made in China, model DPL-1688, wall charger works well and also sports a USB connector for charging. It came from http://www.dealextreme.com/details.dx/sku.4071 and only costed $3.96.