20x4 lcd display

Build a date/time clock with temperature/humidity sensor. All is working well if connected to usb. If connected to external 9 volts battery backlight fades and starts to flicker. Has anybody an idea how to fix this. It's my first prtoject.

You are almost certainly using a 9v PP3 battery. Get a proper battery, like 6xAA, PP3s have no power at all.

Thanks, I'll try.

Another option I forgot to mention is 2x18650. I have yet to use mine but I would guess they are the coming thing.