Electrochemical batteries are of great importance in various technical systems. The stored chemical energy can be converted into electrical energy and supplied to the consumers on demand. Lithium-ion batteries are common in a wide range of commercial applications in the low power range like portable electronics. Recently this battery technology is propelled by applications in the higher power range like energy storage in electric vehicles and renewable energy generation. In particular electrochemical batteries play a key role in the successful integration of renewable energies into the power supply market. In this paper a simulation model of a lithium-ion battery which is integrated into a hybrid power generation is discussed. Special attention is paid in the evaluation of the electrical behavior. The modeling approach as well as the comparison of simulated and measured results is presented.