The big problem with nanoVNA integrated batteries is the IP5303 charger current being fixed at 1A. 1 Amp is too much for any small "pouch" battery. IP5303 IC is designed for powerbanks, using one or more cylindrical 18650 cells that could take that amp.
My nanoVNA came with 0.8mm back and front PCBs, so the swelling is more evident than in other units with 1.6mm thick back.
I have finally replaced the 602040 450mA battery with a 800mAh Samsung AB463446BU. It's a bit thicker (4.8mm), so i had to add a washer over the hex spacers. Otherwise it fits nicely. I hope it can cope with the 1A charging current without exploding.
