The intelligent managing circuit has been widely applied in battery and battery pack design. The usual intelligent managing circuit protects the batteries by controlling over current, over voltage and temperature. It works well for the battery packs which have fewer batteries in series/parallel connection. However, for battery packs with more batteries, the design of intelligent managing circuit should also consider the battery capacity balance function. It will help to eliminate the negative influence which is caused by the difference of self-discharge, temperature sensitivety, charge efficiency and capacity performance of each cell after repeated charge/discharge process. It also helps to improve battery packs’ performance and life time. The LED display of capacity (voltage and current) could also be added in the managing circuit according to customer’s requirement. The following figure shows how four Li-ion batteries been put in series with protect circuit (IC model MM1414):