u/External_Key8021

So I got a message saying my start/stop was disabled. And the vehicle is having trouble starting. I took it to autozone to have my main battery tested and they said it was going bad and most likely the auxiliary battery was bad causing my main battery to drain. So I took everything apart (the hard way, by going through the fuse box not through wheel well) and discovered there was no auxiliary battery at all. Could I have just replaced my main battery to fix the issue instead of buying both batteries? Are those two red cables that are attached to my main battery terminal normally supposed to go to the auxiliary battery?

Thank you.