Plantronics CS540-XD Wireless Headset Battery Li-Pol, 3.7 Volt, 140 mAh - Ultra Hi-Capacity - Replacement for Plantronics CS540 Rechargeable Battery Replacement Battery for Plantronics CS540- Li-Pol, 3.7 Volt, 140 mAh. 100% compatible with your OEM battery - 3 year warranty. Made with high quality Japanese cells. Synergy Digital is a Registered Trademark