Electrical issues (behaves as if battery not connected)
 

A while back, I started experiencing electrical problems with my 2015 JK. Sometimes it won't start, and it acts as if the battery isn't connected at all (dashboard lights, etc won't come on). And occasionally while driving, many of the dash error lights would start flashing (ABS, check engine, etc). I had to take it in to the local Jeep dealership to get a state inspection since I moved to a new state, and I asked them to take a look at it, but of course they just said "it must be because of all the after market stuff you have installed". After a lot of trial and error of disconnecting everything and reconnecting them one-by-one, I discovered that it seems to be the additional battery terminals that I had installed to hook everything into. After removing those terminals and connecting everything to the original battery terminals the problems ceased, at least for a while (more on that later).

Here's the terminals I had:
https://www.quadratec.com/products/17004_9003.htm

I still occasionally have this issue, but it's much more rare than it used to be. I believe this is because I still have one of the little posts from those battery terminals installed since I couldn't find the original screws / nuts that were on the battery. When this problem occurs now, I often don't even need to jump it, I can simply open the hood and touch this battery terminal post, and then the electrical system comes back on and I can start it normally. This makes me think that it's not being properly grounded.

Anyone know where I can buy the original battery terminal hardware? I'd even be okay if I had to buy all new terminals (not just the screws, nuts, etc)

Are you clamping on the terminals and keeping the pressure applied while you tighten them up? That seems to be the difference in the new style terminals and an issue people have. I replaced mine with heavy duty ones but I have an older model with different style terminals than the current style so it was easier to mate the harness and my new terminals.

Have your battery checked at an auto parts store. It might be time for a new one.