Use outlets with APU turned off

Not when thy areally tied directly to the apu. You will need a separate inverter for that.

 

What type/brand APU do you have?

Typically if it's a generator driven type like the Comfort Pro from Impco, you have to have the APU on.

One way to get around that is to install an inverter

 

I know when the apu is off ( thermo pack ) in the truck I was in it would run the batt down .
Now I have no apu but in the bunk area I have a voltage warning indicator that warns me how much voltage I have when my truck is off and I'm using my invertor.
I honestly run my truck while my invertor is being used .

 

If you have to run the engine or APU to get sufficient output from your inverter, then sounds like they have you running on absolute minimum battery count (probably 3 small batteries). If you have 4 big batteries, you should be able to run a 1500 watt inverter for 5 hours before drawing down to any sort of a critical level. But if you only have 3 small batteries, then you might have to always have supplemental voltage to run the inverter (truck alternator or APU trickle)

 

Without causing harm to your batteries, you should set up your comfort pro's battery monitor. You'll need a decent volt meter but you should take a reading off your batteries, go to your display and you'll want to select "calibrate voltage," then set your battery monitor to the minimum voltage. When the apu drops below set value for 10 minutes the apu kicks on for 90 minutes.