The battery is built into the frame, into the downtube. This is practical, invisible and well protected from external influences. It is inserted through a lockable 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 an LG Li-Ion battery with 336Wh capacity and an average range of 70km. You can find out everything about the battery here.
The battery inside the Ampler e-bike is hidden in the downtube of the frame