Sennheiser SET100-J Cordless Phone Battery Ni-MH, 2.4 Volt, 80 mAh - Ultra Hi-Capacity - Replacement for Sennheiser BA90 Rechargeable Battery Replacement Battery for Sennheiser BA90 - Ni-MH, 2.4 Volt, 80 mAh. 100% compatible with your OEM battery - 3 year warranty. Made with high quality Japanese cells. Synergy Digital is a Registered Trademark