Capacity Extension: Compatible with Jump 600X. Expandable capacity to 939Wh. Super Safety: The Jump 600X Extra Battery is a built-in premium LiFePO4 Battery. Besides, it has LIFEBMS that can provide multiple protection for the battery. Durable & Economical: With an extra battery, it can provide more juice to run your essential devices and appliances for hours. How To Charge: Connect the extra battery with the Jump 600X power station, then recharge the extra battery through the power station. Easy To Carry: With a sleek, streamlined frame design and a durable, solid handle, its easy to carry around.