Hi Tangogow,
I want to replace the battery in an Alta HR.

Bought two batteries:
Aliexpress: 45mah Ersatz batterie für Fitbit alta hr WL-FBT07 2-Draht
Amazon: Ersatz für Fitbit FB407 für Smartwatch Uhr Fitnessarmband (45mAh, 3,7V, Li-Polymer)
Seems both are the same and for Alta, not Alta HR.

Need information about type of battery and where to buy. Can you or someone else help to get the nessesary information or send me a link where to buy?