Excellent article regarding lithium batteries.
As far as burning out your alternator, the most I have seen through the 7 way cable is 7A.
How to find happiness with lithium batteries
https://www.solacity.com/how-to-keep...tteries-happy/
Charging lithium in cold weather is a big deal. I added two layers of 1" pink styrofoam board insulation to the entire battery compartment. I also installed battery heaters (holding tank heaters, wrapped around the batteries) for when we are camping in cold weather.
When you reach your overnight stop you will need to warm up the batteries before charging them.
Maybe a small 300W plug in heater In that compartment.
I'm currently using one of these due to the extreme cold weather
Wall Space Heater 350W&450W Remote Portable Electric Heater with Programmable Adjustable Thermostat, Overheat Protection, Precise LED Display, CSA Certification Safe Heater for Office Dorm Room
https://a.co/d/8oCp7e3