Vtech BT291665 Cordless Phone Battery Li-Pol, 3.7 Volt, 240 mAh - Ultra Hi-Capacity - Replacement for Plantronics BT-191665 Rechargeable Battery Replacement Battery for Plantronics BT-191665 - Li-Pol, 3.7 Volt, 240 mAh. 100% compatible with your OEM battery - 3 year warranty. Made with high quality Japanese cells. Synergy Digital is a Registered Trademark