Update: Now with JLCPCB and 3D print files.
Some time ago the local danish supermarket chain Føtex held a loyalty campaign where you got a sticker to put on a collector card every time you purchase goods for 50 DKK and when you had e.g., 25 stickers you could buy a commodity with a discount. This time it was Black+Decker power tools and both my brother and I did this and bought some very nice 18V 5Ah Li-ion batteries pack and then we got the obvious idea that they could act as a power bank if only we could design a PCB that could connect to the battery terminals and 3D print a holder which could slide the PCB onto the battery pack and hold it in place. The PCB could then feed power to a car adapter outlet with QC (Quick Charge) and PD (Power Delivery) functionality which could provide lots of power e.g., a 65 Watt Baseus.
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3D printed holder in grey PLA, PCB is fastened with double sided adhesive tape