I bet this has probably been asked here a thousand times before, but how do I make a Pro 106 display how much juice is left in its batteries? I always run it off of NiMH's and leave it plugged into the wall with the AC adapter that matches what's in the manual when I'm not using it, but I drove out to Lapeer from the Flint area yesterday (about a half hour drive) and had it on the whole time without it being plugged in and my batteries were about to die after about an hour of sitting in the car watching trains at the Amtrak station, so I had to plug it into the DC power supply. I thought this was odd because they usually last several hours. They're old (probably over two years, if not more), but I didn't think they'd die that soon. I did what's in the manual but all that says is volts left, and I'm looking for a percentage. Also the battery level icon always blinks an empty symbol when it's plugged in but it's gone completely when it isn't. I'm using the yellow battery holder not the black one like the manual says and have the settings at NiMH as well. Thanks in advance for any input.