As an aside, pretty much all the g604 is will end up with double click reliability issues or an inability to hold down the mouse button and drag. But you can easily replace the switches or there's vendors on eBay and AliExpress that I'll sell you a circuit board with the switches pre-soldered for replacement.
My Logitech G604 works fine on NiMH. The calibration for reporting battery charge as a percentage is off, but it runs for months.