I am relative new to flying, but I have found that charging the xmtr and RX batteries overnight with a wall wart, doe's the trick.
Another atvanatge is to install a Volt watch meter. It tells you battery status, but that all. You need to chek the actual battery charge capicity with a Sentry, which put's a small load on the rx battery. It will tell you go or no go.
Just my 2C's worth.