18650 lithium ion battery pack 11.1V 3200mAh is rechargeable and safe
Amazon.com: Rechargeable Lithium Ion Battery Pack - VIDAR 3.7V 10400mAh High Capacity Li-ion Battery Pack with JST PH2.54/2P Plug-in(Customizable) for Electronics,Toys,Lighting,Equipment : Health & Household
Canon Rechargeable Lithium-Ion Battery Pack for LP-E12 6760B002 - Best Buy