Many people are complaining about poor battery life after deploying the latest iOS 10.1.1 software update on their iPhone, which released for public consumption on October 31 and squashed bugs where Health data couldn't be viewed for some users.
Aside from this, it seems that iOS 10.1.1 is also causing some iPhones to shut down abruptly when the battery charge falls below a certain percentage, according to a thread on Apple’s support forums that at post time had thirteen pages.