The dual slot charger is a good idea if you need to keep a hot second battery. I use mine with a StarTAC ST7867 and an extra Lithium Ion extra capacity main battery. The documentation that Motorola provides consists of a single sheet sectioned into 15 1.5&quot; x 2&quot; rectangles printed front and back in 27 different languages (this is not an exaggeration). Something that is not made clear is that there are two spring-loaded black plastic tensioners in the spare battery slot. Since they are not readily discernable, if you are not aware of them it will seem as if the extra capacity main battery will not fit into the slot. It takes some jockeying, but the plastic tensioners move toward the phone charger slot to make room for the spare battery, which is inserted contacts down and facing toward the power supply connector. After the battery is inserted, the tensioners keep pressure on the battery so that the battery contacts are held firmly against the charger contacts.