Battery monitor

The old LED style battery monitor that I had fitted to the 12v system was fine but I found that it was hard to read and I had to remember the combination of flashing lights to work out battery voltage. I have now removed this and fitted a new much clearer voltage readout that will monitor my 12v system, or at least the battery plugged into the 12v circuit. When the rear door is fitted it is also much more visisble so monitoring battery voltage now should be much easier and also I can see when I have to switch batteries over to keep the draw on them even. The only thing that concernes me about this new monitor is that it is backlit, will this drain my batteries faster, the backlight might have to go?
The mini gun is virtually finished and all that I need to work on now is a more solid bracket to hold it to her shoulder.