It is not a model with a built-in battery, which can save a lot of worry, but: the built-in battery is a drawback 1. Generally heavier than the dry battery 2 battery life is fixed, not easy to replace 3, expensive advantages 1, worry ah 2, integral design is not prone to failure 3, beautiful use of two or three years can choose the whole battery, pay attention to light and long time use can choose the dry battery.