I bought a graco dual monitor monitor model 2795. I have plugged it in, put new batteries in the nursery unit and have been charging the rechargeable batteries for days. The side button is green, I assume meaning it is charged and or charging. The problem is when I take the dual monitors off the base charger, the unit goes dead and does not work. What am I doing wrong. I want to be able to take the portable monitor and clip it to my clothes to work around the house. Help and Thank You!