Rechargeable Standard Battery, 800mAh, NiMH 1.2V
From Amazon
ANSMANN AAA DECT Phone Batteries [Pack of 3] Rechargeable 800 mAh NiMH High Capacity AAA Type Size Battery For DECT Cordless / Portable Phones
Conrad Electronic
Ansmann DECT maxE HR03 AAA battery (rechargeable) NiMH 800 mAh 1.2 V 3 pc(s)