How to prevent drain in a smartphone battery

Network use, videos, messaging - all are a drag on a smartphone's battery. To reduce drain, users should take advantage of all of the energy-saving functions of their device, Germany's Mobile Phone Information Centre (IZMF) advises.
For example, many Android devices have an energy-saving mode that disables power-hungry functions when they're not needed. Another piece of advice is to use wi-fi whenever it's available because it uses less power than 3G or LTE.