STK's Panasonic P-P511 NiMH 2200mAh Phone Battery - for Panasonic P-P511, Energizer ER-P511, ER-P507, and these Panasonic cordless phones 2200 mAh NiMH = longer talk time!!! Over 100% MORE POWER!!!!! NiMH does not have the memory effect like NiCAD 3.6 volts. Compatible 2.4 GHz and 5.8 GHz Phones Quality Products @ Great Prices .... Guaranteed SterlingTek!!! Serving You Since 1999! 1 Year Warranty: We will replace this or any other item that you purchase from us. We always sell new high quality items and we are willing to back them up @ SterlingTek!