ya the battery is 11.1v
nice, a 3s lipo by the looks of it 
do you want to consider powering your arduino and your motors with separate batteries? Just more juice so your thing won't suddenly drop out of the sky when the batteries run out! Also MCUs tend to do funny things when underpowered, so possibly a safety issue here (quadcopter = four high speed blades spinning = trouble!). Using another battery for your arduino could solve this problem, as with a central battery, you probably want to fly your toy till the batteries die, right? If your MCU shares this power and isn't getting enough once the four thirsty motors suck it all up, you could end up with a messy situation! However, if you give your MCU ample power by having a 2s 2500mAh lipo, for example, then your motors would drain their battery long before your arduino drains its. Worst case scenario, your quadcopter breaks. No ugly situations where it flies into someone! Just remember to charge BOTH batteries when you take it home though 