Flashlight with high power are normally not usable with batteries as
they have only 1.2.
Normally in newer LED flashlights are high-performance special
Battery with a protective circuit.
After my reply that it (neither a high nor a flashlight so with LED) is a small children's flashlight, the answer came:
Nevertheless, this must be approved by the manufacturer for use with rechargeable batteries, as these only work with 1.2 volts.
Presumably, the electronics of the lamp is not designed for 1.2V.
Very professional, customer-friendly response of a "professional" company !!!!
No more battery-Online GmbH