Difference between the 2018 standard and 2019 Premium both with manual transmission

[Rod Las Vegas]

My question: What is the difference from the 2018 standard model and 2019 Premium both with 6 speed manual transmission. I have a 2019 Premium and using it as a tow car (4 wheels down) behind my motorhome. I'm having problems when I tow it the battery goes dead. I tow it with the key turned to the ACC. My friend has the 2018 standard with manual transmission and he can tow it all day long with no battery drain. Why is that?
I've installed a charge line from my motorhome to the crosstrek hoping that will take care of my drained battery problem.

Does anyone have any ideas. I don't want to tow it and then have to jump the battery at the end of the day.

Thanks
Rod