The Goal Zero NiMH Rechargeable AAA Batteries (4 Pack) are designed for use with the Guide 10 Plus charger and form the basis of a very mobile power source for small appliances. The Goal Zero batteries are rechargeable up to 500 times before needing replacement. They will reach full charge in as little as 2.5 hours via a Goal Zero solar panel or a USB power source. These batteries have a low self-discharge rate so they can sit unused for 12 months before they start to lose effectiveness. Unlike alkaline batteries Ni-MH batteries will maintain almost full power throughout their usage cycle. This pack includes an adapter needed in order to use AAA batteries in the Guide 10 Plus charger.