My Skydat DX2 is giving me some problems. After about 30 or so minutes of use it start fading until it eventuall goes blank

My radio is also playing up. Seems it is not always charging from the mains. After a bit of flying the battery light start flashing.
Could both of the above be related to my battery being flat?
Plane does not want to start. So a few pulls and all ok, battery sometimes gets charged so it then starts with ignition but maybe only once. I wouldnt think that the battery effects the electrics once you flying as power comes from aerie?
Any input?
