Alright I got two of these 8x8 led grids set up on a bread board http://dx.com/en/p/max7219-dot-matrix-module-w-5-dupont-lines-184854#.Uv2teP2FVSU and I have one of these lcd displays http://osepp.com/products/shield-arduino-compatible/16x2-lcd-display-keypad-shield/ I have two push button switches with a 10k ohm resistor each. Oh yeah lets not forget the smd uno board as well. everything is on a bread board. I attached a 9v battery to Vin and Gnd and I got 1.5 hours before I could no longer read the lcd display. I then tried 3 AA cells in series, I just soldered wires to make the connections, wrapped a bit of tape around the batteries to hold them together. Although the lcd wasn't as clear , as the 9v battery initially made it, the 3 AA batteries lasted for 3 hours, before I could no longer read the display. I know why the lcd wasn't as clear with AA battery set up, as it was with 9v.. 4.5 v only and not 5. So can anyone tell me why I got more duration from the AA batteries, then I did out of the 9v?
Thanks Larry, good link, that cleared it up for me. If I am going to calculate my load current I would have to add all the LED's of 128 and 2 max 7219 and 1 lcd screen, as well as the arduino?