Inverter and apu

[Jamescj212]

I have a 2010 prostar with cummins isx. This truck has a 1500 watt inverter i installed. It also has apu that came with international as stock. I have the inverter running off of the main batts and not those of the apu. However a couple months ago i had to replace the starter and didnt put in the 1 it called for which was very very expensive on the road. So, the voltage reads just fine at 14.1 would you run the inverter off the apu or the main truck batteries? There is no issues im aware of , just asking for gen knowledge. Thanks