Hello,
Does the XBee respond to an ND request while sleeping?
For example: my application sends an ND request every few minutes. If any of my modules are sleeping at the time, will they then not respond to the request?
I don’t see how they could - sleep mode is the lowest power consumption, and having the receiver circuitry active would mean consuming power continuously.
When a module wakes from sleep, it can be configured to sample its active input lines and send a sample packet. If you configure all your end nodes to do this, you’ll find out who’s out there without needing the ND command. I haven’t tried this myself, but it looks as though it would work.
Makes sense. Thank you for the suggestion!
Any idea perhaps how long a module could last connected to a 9V battery when not configured for sleep mode?
Well, it’s easy enough to work out an approximation. The product manual says the receive current is 50mA for an XBee or 55mA for a Pro. Then you just need the battery capacity in mAH. For a cheap rechargeable PP3 battery, that would be about 200mAH, so you’d expect a battery life of 4 hours: less for a Pro, and less still in proportion to the amount of transmission done. Less again if the battery also has to power external circuitry or if the XBee is supplying current through its output lines.
Then again, a battery with a higher capacity would increase the figures in proportion.
So that should give you a rough idea - if you need something more exact, I’ll leave to you as an exercise 
Perfect. Thank you!