Can't figure IBS and Battery issue

[Micheal-4458]

E60 550i 2006
(Before I discovered the issue and ISTA, I changed the battery twice. Even after installing a new one, I still notice that the lights dim significantly when I throttle and start the engine barely each morning)

Just figured out ISTA and scanned for fault codes, got this:
CDA2 (power management, battery voltage 0x3B4) faulty, receiver DME, transmitter CAS/PM.
CDA3 (power management, battery voltage 0x334) faulty, receiver DME, transmitter CAS/PM.

E714 (Battery voltage, 0x3BE) faulty, receiver IHKA, transmitter DME-DD3
E716 (Consumer load, 0x3BE) faulty, receiver IHKA, transmitter DME-DD3
(couldn't find any solution or anything about those upper 4 errors)
ALSO
Maybe those also have relation?
E204 PDC:K-CAN-Low wire fault
E244 SZM:K-CAN line fault
E5C4 CID:K-CAN line fault

2F80 DME: System time, plausibility
+
Whenever i try to check on service function tab > voltage supply > evaluating the battery state of charge it shows the following:
Engine control cannot recognize IBS. This may be due the following cause:
.IBS supply interrupted
.BSD between DME/DDE and IBS (open circuit, short circuit, loose contact)
------------
I checked the IBS in the trunk and noticed that the positive lead was disconnected. The blue and black connector between the positive terminal and the IBS the wires inside were dusty. I removed it and connected the wires directly, and I noticed some sparking when I did. However, after trying to access the service function again, it still can't recognize the IBS.

From my research, it seems that a faulty IBS typically prevents the car from starting, but that's not the case for me. So, maybe the IBS is still functioning?