Charging Times
What is the output of the charger (McGreggor (JR) do two types)
What batteries are we charging (capacity)
General rule if you are using the charger that came with the radio is 14 - 16 hrs and it sounds like its a trickle charger so you cant fry them but I would stop at 16hrs.
They should also be 'freshly charged' eg not last week. A battery checker and a monitor is a good investment for you RX batteries.
Nick