AvMap Power question

I just installed my AvMap IV in my panel via an AirGizmo mount. If I don't install the AA Nicad backup batteries in the device, when I turn on the avionics switch, the AvMap will automatically turn on also (if it was on when I last turned the avionics switch off). If I turned the GPS off prior to killing the avionics power, when I turn the avionics power back on, I have to manually turn the GPS back on.... this is all great and works the way I want it to. However, when I install the backup NiCad batteries, if I turn the avionics power off with the GPS still on, the GPS switches over to battery power and remains on until I manually turn it off which is kind of a pain. I would really prefer the unit only go to internal battery power if I manually turn the unit on and there is no external power present. Is this the same behavior every one else observes? Comments?

J.C.