Pixel Pro External Flash Battery Pack For Nikon SB-900 SB900 Flashgun as SD-9 TD-382 is a power battery pack for Nikon Speedlight flashgun . It uses two groups of symmetrical charge system and have more stable charging voltage. It charges time twice as fast as any other battery pack. Flexible and convenient design. You can use 4 or 8 AA batteries freely. It uses a new charging method. You get a fastest recharge when using 8 AA batteries. It saves more than 25% power consumption in stanb-by mode compared with other similar products.