Selecting a battery for a DIY project
I think I will go with a commercial OTS power bank.
This will probably solve my problem the easy way - since those already take care of charging and protecting the cells. There are still criteria the pwoer bank will have to meet: It needs to be able to be charged and discharged at the same time (bypassing the cell in this situation), and have a high output current. There are power banks especially made for notebooks that meet those criteria. A 70Wh power bank should give me at least 3 hours of operation. I may need a buck converter, as my boards need 5V, but laptop bower banks often provide higher voltages, up to 19V.