To follow up on my previous post, I tried hooking up my ICE to the i3 via jumper cables. Unfortunately, the alarm continued to chirp, but the headlights started flashing and the horn was honking with the alarm. Some lights and error messages popped up on the screens, so there might have been something going on. But, the car wouldn't start, HV battery didn't initiate. Since it was 8pm and the car alarm was blaring, I decided to call it a night. Again, closing the frunk and the doors, the alarm stops after a few minutes.
Being over 6 years old, I am pretty sure I'm due for a new battery. I sourced a new 12V from a local BMW. I couldn't wait for shipping from an online retailer. I would recommend calling around (if you live in an area with multiple dealerships) since I was quoted different prices. As I mentioned in my previous post, my alarm would go off as soon as I opened the door (I unlocked the door with the key since the keyless entry wasn't working). So, with the alarm chirping, I manually popped the hood, took out the cubby, flipped the HV disconnect, took off the bracket, disconnected negative, then the drain hose, and alarm stopped when I disconnected the positive terminal connection. Overall, not too difficult, just wish I wore ear protection while I did this. Picked up the new battery. Plugged up the new battery to a Battery Tender and let it charge overnight. Installed the new battery the next morning and as soon as I connected the negative terminal, lights come on and screens lit up. It's alive! Only thing I needed to do is correct the time and date. Other than that, seems like nothing happened. Even my radio station preset were saved. I did not do the battery registration, still debating if I need to do that. So, in summation, as soon as "discharge while stopped" message appears, and your 12v battery is 4-5+ years old, get the battery replaced before your i3 becomes a brick. Thanks to the MyBMWi3 community for your feedback!