2S4000-LiFE : 6.6volt 4000mAh rechargeable Li-FE battery for RC hobby. Includes JR-HiTEC-Futaba-SPEkTRUM receiver connector, Red T power connector, and white Balance Charge connector.  This battery can typically be re-charged with an RC Smart Charger designed to be capable of charging Li-FE batteries. These Lithium Polymer batteries HOLD THEIR CHARGE when not in use.
Specifications:
Capacity (mAh) 4000mAh
Number of Cell(s) 2
Dimensions 135 x 63 x 14 mm (5 1/2" long, 2 1/2" tall, 1/2" thick)
Recommended Charge Rate 8A (2C)
Balance Connector XH (also called JST-XH, Align type, the most popular type on the market)
Power Connector T Plug (Deans Ultra compatible)
Net Weight 225g, 7.9 oz

Recommended charger: H6AC (works for Li-FE, Li-ION, Li-PO, NiCd, NiMH)