Through the years of development, network stability was only based on so-called conventional generation units. In recent times, when mankind is looking for more environmentally friendly and renewable solutions, energy produced by wind turbines seems to be the most promising of renewables, mainly due to the abundance of the wind resource. But, beyond its many advantages, wind energy brings new challenges for the stable operation of the power system. Wind turbines are producing energy only when the wind is blowing, and its power level varies significantly (to the third power), depending on the wind strength. Wind turbines' intermittent, partly unpredictable power production introduces variable power to the grid. That changeability has to be compensated by other (usually fossil based) conventional generation units in order to assure grid stability. However, the higher the percentage of installed wind capacity, the higher the problem of wind integration into the power system and the need for more conventional units that can handle the variable power production of wind turbines. Energy storage addition to wind turbines is one of the most promising solutions to problems related to integration of wind power into the energy network. Not only can it decrease the wind turbine's variability, but it can also decouple moments of energy production and generation. Lithium Ion batteries and especially Lithium Iron Phosphate (LFP) batteries can be characterized by high power densities, relatively long life-time, no maintenance and a lot of research currently being done on increasing their performance. Therefore, they seem to be a good choice for integration with wind turbines. However, the current Lithium Ion energy storage price and its limited lifetime are the main obstacles to the integration of storage technologies with wind turbines. That is why proper lifetime estimation of the lithium ion batteries, working with mission-profile characteristics for specific services, is very important, not only for optimisation of the revenues but also for correct scheduling of the maintenance jobs. This paper analyzes the connection of LFP battery storage systems into wind turbines, with a high focus on the lifetime of LFP batteries for selected services.