To purchase this type of rechargeable battery mainly consider capacity and specifications and prices. First determine the size of the purchase of batteries, for the battery compartment relatively small equipment, or the need to place a plurality of battery devices, pay attention to the purchase of high capacity, the diameter of the thicker battery is suitable. The cathode of the rechargeable battery also has two different forms, one is similar to the ordinary battery with some protruding parts, to help with the battery box or other battery cathode contact good, there is a flat battery cap, more suitable for welding into battery block. It is recommended to use the previous form of rechargeable batteries better. Packaging rechargeable batteries are divided into industrial packaging and retail packaging, industrial packaging only monochrome plastic skin, the main supply of manufacturers to do battery block, a single battery on the production date in addition to no other information. and retail packaging looks more beautiful, there are detailed representations including brands, trademarks, capacity and Origin, and other information, and some with a simple charging method, suitable for ordinary users. The second is the choice of battery capacity. For digital cameras, flash, communications equipment, such as power consumption of equipment, from the working time and performance considerations, large-capacity Ni-MH battery is the preferred, large capacity of the battery can be used after a sufficient time for longer. The number 5th battery can reach the 1200-1300mah,7 number of 550mAH, almost twice times the low capacity Ni-CD battery.