Accumulator products of P.T. "X" that have accumulator of 221 CA can not fulfil Japanese, Europe and U.S. standards that require minimum cranking ampere of 275 CA. By using fishbone diagram suspected affecting factors to accumulator cranking ampere are obtained. Company chooses factors that are allowed to be experimented. There are 4 chosen factors. Each factors has 3 levels that are charging time interval (30 minutes, 60 minutes, 90 minutes), cell plate thickness (1.2 mm, 1.4 mm, 1,6 mm), material purity percentage (96%, 97%, 98%), and charging current (160 A, 170 A, 180 A). From the data, the experiment combination is done by using orthogonal array that is one of the Taguchi's method steps. From the analysis the best combination is obtained that is charging time interval of 60 minutes, cell plate thickness of 1.4 mm, material purity percentage of 98%, and charging current of 180 A. This combination can increase cranking ampere to 278 CA. Verification test proves that cranking ampere of 278 CA can be attained.