A technical small device no longer works, mostly the coin cell is empty and depleted. Of course, the appropriate Knopzelle is not strictly hoarded "Battery assembly camp".
Single button cells can be very expensive in consumer electronics store.
This coin cell range you are equipped for all cases. In most technical equipment is one of 12 different coin cell.
I've saved with this assortment a lot of time and money, because I just had the right button cell at hand immediately.
Absolute buy recommendation -> should be in every battery-collection.