You could do that to your transmitter if it has a voltage readout and turn it off when it gets to about 1.1 volts per cell(8.8 volts for an 8 cell battery). But I would not do that with the receiver because you risk discharging the batteries until they are completely dead which is bad for them. I would recommend investing in an inexpensive batter cycler so you can monitor how well your batteries are holding their charge. You can find good deals for a used one on ebay or some place like that.