I wanted to get a spare battery anyways, but now that the battery currently in the car has given out on me (it appeared to be dead, then a bit later it was working again) it’s more pertinent. I can get a used car battery for $40, I think.
CashApp/Venmo: allthetimesivedied
You shouldn't buy a used battery imo, wait until you're able to afford a new one. It might be twice as expensive but it will be at least twice as reliable, especially with it getting cold.