Nitro/gas plane battery Help needed

I fly a lot of nitro and gas planes but have old NiCad batteries in them. I have now had 3 crashes on one plane because I did not know weather the battery was fully charged or not. I was wondering if I could use a life battery to power my receiver and servos without any work. I don't know anything about life batteries and think this would be a great answer to my problem. If any one has done this or something similar, please help.
Thanks