No, you don't need to buy battery, this 3in1 carbon monoxide detector is built-in high capacity 2400mAh battery, it can Continue working 90 hours with full power. 

yes 

We re-write the mode to a power-saved design. the CO detect's screen backlight will turn off if there is no operation after 1 minute, but the CO detector the carbon monoxide, humidity, termp in 2 seconds. Pls don't worry about it. If the CO detector is in low power, the alarm will sound ""di"" per 1 minute. This new poer-saved mode helps to increase the continue working time to 60 hours with full power. 

For the same size tripod, carbon fiber is about 30% lighter than aluminum. There are the advantages of the carbon tripod: more stable and not rusty. But it is more expensive than aluminum tripod. 

max load of this carbon fiber tripod is 10kg/22lbs