OM System BLS-50 Lithium-Ion Rechargeable Battery

The BLS-50 is the small-body battery in the OM System and Olympus line, fitted to the OM-5 series, the E-M10 bodies and the PEN cameras. 1210mAh, and rated for up to 500 charge cycles, which on typical use is several years before capacity is noticeably down.

It charges in the BCS-5 external charger or in the camera over USB on bodies that support it. Compact enough that two spares add almost nothing to a bag, which is the usual answer for the smaller bodies whose battery compartment is sized for portability rather than endurance.