My #Librem5 extra #battery arrived and I put it into the no name charger I bought to charge it.
It'll take some time to charge it until full (calculated with complete ignoring voltage and loss it should charge from 0mAh to 4500mAh in 7.5 hours), but this allows me to use the phone on battery while charging the backup battery.
Nice to know I can run out of battery once away from home without loosing connectivity.