The battery Senco 6v 1500mAh 1.5Ah Ni-MH has a capacity of 1500 milliampere hours. This indicates the current of the battery and is indicated by Ah or mAh. Is the capacity high? Then it takes a long time before the battery of your 6v tool is empty. Is mAh lower? Then you will have to charge the battery more often. With more mAh your machine does not become more powerful!