This is weird issue that came up with some of my 128x64 ST7920 LCD's. I have the LCD 5v running off of the nano and the back light running off of the 3.3v on the nano. When I run the nano & LCD's off of my power supply or USB from the computer they work fine but when I hook them up to a 3s 12.4v lipo something changes. When first turning it on from the battery the lcd pixels will all light up white(blue background lcd). Then when I turn it off and back on it will be dim and I have to readjust the intensity control on the back. This seems really weird. Any ideas why display would do this?