Battles that users do not need to manually close applications from the multitasking panel, have been going on for years. How many do not prove that this does not make sense, many still activate the multitasking mode, then "kill" each application. And repeat it sometimes several times a day. So is it worth it to close running applications on the iPhone / iPad for the sake of battery saving?
Applicants of Apple have already informed users that there is no point in this. The application does not select RAM, it "freezes" and does not use the resources of the smartphone when it is in multitasking mode. On the other hand, the system can receive information faster when the application is running, because it needs to be updated, not restarted.
And the other day independent developer Hiroshi Lockheymer noted that such a practice can be detrimental to a gadget. Restarting gives additional load on the processor, followed by faster battery discharge. As a consequence, manual shutdown of applications is fraught with faster discharge of the gadget with daily use and faster consumption of the battery itself. So no, multi-tasking applications do not interfere with your device.