Check the listing for details. Goal Zero Yeti 400 Power Station With Auxiliary Battery And Charger. Condition: Used. Listed at 244.99 USD. The old internal lead acid battery was replaced for an upgraded LITHIUM Lifepo4 battery. The new battery is half the weight and can fully discharge down to empty without damage compared to the old lead acid battery. Added an additional outside battery that plugs into the side of the main unit. Combined watt hours is 512wh. NOTE: The only issue is that the inverter does not work, but everything else (12v cigarette lighter port and USB ports) work perfectly. Will include a wall charger as well. The Goal Zero Yeti 400 Power Station (AGM/Lead-Acid version) receives charge through three primary methods, typically using the 8mm blue-ringed charging port located on the front faceplate: Wall Charger (AC): Using the included AC wall charger, it can be plugged into a standard wall outlet.