Simply remove the two screws on the bottom, remove the battery connector and plug in the new one. Then revive your robot.
LabTEC 14.4V 4000mAh Replacement Battery for Eufy RoboVac TW4-11 11S 12 15C 30C
2x Zeee 6S Lipo Battery 4000mAh 22.2V 100C EC5 Softcase for RC Airplane Heli Car
Gtech CLM 36V 4Ah Lawn Mower Battery Model 121A0025 4000mAh
Digital TV Video Player 4000mah Battery 10 Inch Portable Digital TV For Car Home