My standard 2011 Kia Soul’s positive battery terminal became very corroded and after having to jump it in order to get it to start, I took it to Walmart for a new battery. After they replaced the battery, the car engine wouldn’t start at all. They tested the battery a few times and it was charged and fine, should have worked. They then replaced the terminal (I’m not great with cars or terminology, but I mean the metal connector between battery and cable). They tried again, engine still wouldn’t start. At this point, from what I understand, they “trimmed” the slightly corroded part of the cable leading to the positive battery terminal, but still wouldn’t start. Eventually one of the mechanic used a tool to “ground” the battery and it started. They tightened all the terminals and sent me on my way, 4 hours later. It turned on and off 4 times that day, then sat for 24 hours. Now it won’t turn on again. The lights, dashboard, radio, everything else turns on, but when the key is turned, the engine doesn’t do anything at all. What could be the issue and how much money am I looking at spending? My warranty won’t cover “maintenance”, so they likely won’t cover this.
It looks like the problem is not with the positive terminal on your battery, but somewhere on the negative side. That could be a bad electical contact on the negative battery terminal or the cable connected to it. It could also mean that there is a bad ground connection somewhere else on the vehicle(*), for example near the starter motor. There is some electricity running because the radio and dash function, but the high current of the starter motor cannot be sustained through the weak electrical connection that you have now.
(*) The entire car chassis is connected to the negative terminal of the battery and as such can be used directly as a ground for various electrical components. Your vehicle will have grounding points all over, sometimes very visible (a cable connected to the chassis) and sometimes more subtle, such as the mechanical connection to the engine block.