Most people will tell you that using a fully charged 6v battery on a reciever won't hurt the reciever.. I have done so and I think that I actually blew two of them in two separate planes.. When you fully charge a 6v you can get up to 6.8v(at least I have seen this with mine).. The more volts the better power and speed you will get out of your servos but I think I over did it on mine.. Especially if you have an older reciever I would say regulate your battery down to at least 6v so that a fresh battery wont fry the Rx.. This is my opinion and you will hear many..