LG VX-8100

I have had my 8100 for about 4 months now-coming from the 6000 and my biggest frustration is that when the battery is low and i am on a call, i get no beeps, no noises to indicate that the battery is low and then all the sudden it powers down WITHOUT NOTICE in the middle of my call. I have searched through all the tools/alert sounds etc and there is nothing for a low battery signal. does this exist? is there a way other than the blinking for the phone to tell me it's dying? HELP PLEASE!