So I've bought batteries from LIDL labeled PAPS 208 A1

The specs are quite nice for the application I have in mind:.. a DIY ebike !

• 20V 8Ah (6S2P) 21700 type cells 
• High current < 100A
• Bluetooth :
  • Settable discharge min discharge of the cells, 
  • Settable maximum output current
  • Reading of charge / discharge current
  • Reading of temperature
• 60 Euros in France.

I've also bought a dual fast charger (not "smart") for 28 Euros.