Key Features For SKM 6000 and SKM 9000 Transmitters Rechargeable Lithium-Ion 5.5-Hour Operating Time The Sennheiser BA 60 is a rechargeable battery pack for the SKM 6000 and SKM 9000 handheld wireless transmitters. It provides up to 5.5 hours of operating time on a full charge. To recharge the BA 60, the L 6000 charger and LM 6060 charging module (both available separately) are recommended. As an alternative, the L 60 charger can also be used.