The battery is built into the frame, into the down tube. This is practical, invisible and well protected from external influences. It is inserted through an opening on the bottom bracket shell. It can be removed in case of service, read more about this here.
The battery is charged via a charging socket near the bottom bracket.
It is a Li-Ion battery with 336 Wh capacity and an average range of 70 km. You can find out everything about the battery here.
The battery inside the Ampler e-bike is hidden in the down tube of the frame