Along with the development of battery, the maintenance of battery becomes more and more important, performance measurement and capacity measurement of battery are needed. Moreover, the refreshment of the charge technique should not only feet the charge/discharge requirement of new battery, but also improve the quality of charge/discharge of battery, prolong the operation life span. The text discusses the choice and compare of several filters, on the basis of the demand of circuit in the process of charge or discharge. Finally, the T-filter is chose, the text analyze the dynamic response characteristic, especially when the load is capacitive load, analyze the response function, and the discussion of several physical quantity relatively. In order to eliminate the harmonic component and advance response speed, we design the filter parameter in particular