These are rechargeable EH brand LiMn2O4 (commonly referred to as Lithium Manganese or LiMn) batteries. They are safer chemically than Li-Ion batteries and do not need a protection circuit. These cells can handle high amperage and are safe in series or in parallel. They can be charged with any Li-Ion battery charger with an output of 4.2V. These have a button top. They are 3.7V batteries that are rated for 2000mAh. Battery cover may vary but the batteries are always high quality and accurately rated.