I bought a charger for the batteries at
https://www.subtel.ch/index.php:
Charger VW-BC10 for Panasonic VW-VBT190, -VBT380, -VBK180, -VBK360, -VBY100 (HC-V777, -V757, -V380, -V270, -V160, HC-VXF999, HC-W570, -W580) Charging cable Power supply unit.
SKU: 916211
I find it more practical anyway, especially on holiday - you can charge the 2nd battery while using the camera :-)