2018 Compass. Cold wiped out the main factory battery so I replaced that and my car started. How the start/stop isn't working and about 1/4 of my screen inside is black. I've been reading that aux battery is likely the problem, either low or dead. I have a battery tender and was wondering if I could try to charge the aux battery. Is that a thing? Do I hook it up like I would to jump start the main battery? I know I could probably just replace it but want to see if charging is an option since I didn't have a problem until I changed my main battery.