Data Center industry is booming as a result of dramatic increase in cloud computing bringing new challenges and opportunities. Data centers are important energy consumes, but as in many other cases, importance of quality prevails on quantity. To achieve a high tier classification, Data centers need redundant power supply and reliable backup power source which normally include UPS. UPS use batteries and numbers are impressive: a data center my easily need well over 10.000 batteries. How to monitor, manage and maintain batteries? How can we predict failure and how can we increase battery life and reduce cost? Shall we use traditional or Li-Ion based batteries? Why monitoring systems should be a part of EMS (energy monitoring system) and how can Artificial intelligence, demand modelling and green power sources help to reduce operating cost and improve reliability.