The connector for charging the Duo-Power is a microUSB connector.
An appropriate USB charger is not supplied. (Not only not as stated optimal 1.5A or more charger, but none at all)
According to this leaflet for only 500 charge cycles designed what something appears little. The limiting factor is, experiences of a friend after, but perhaps not the battery cells, but the built-in electronics.
So far, no defects occurred.
The bottom line is exactly what I was looking for.