The EcoFlow RIVER Pro extra battery can double the capacity when connected to a RIVER Pro portable power station. This has the effect of you increasing the batteries capacity from 720Wh (standard) to 1440Wh (RIVER Pro extra battery). RIVER Pro extra battery Capacity: 720Wh. Features: Battery capacity 720Wh Doubles the capacity of the EcoFlow RIVER Pro Increase the batteries capacity from 720Wh to 1440Wh Silent & zero emissions rechargeable lithium-ion battery Fast charging via mains, 12v car adapter or solar panel (optional) Specifications: Dimensions: H:16.5 x W:28.8 x D:21.7 cm Colour: Black Guarantee:2 years Material: Plastic Casing / Aluminium Chassis Model Number: ECORPEB