Avaya 3910 Cordless Phone Battery Ni-CD, 3.6 Volt, 800 mAh - Ultra Hi-Capacity - Replacement for Uniden BT990 Rechargeable Battery Replacement Battery for Uniden BT990 - Ni-CD, 3.6 Volt, 800 mAh. 100% compatible with your OEM battery - 3 year warranty. Made with high quality Japanese cells. Synergy Digital is a Registered Trademark