More electrical nightmares - 2006 Volvo vnl 670

2006 Volvo vnl 670 got 890000 mi Cummins ISX 13 spd, I was going down the road and noticed multiple electrical symptoms, the big one is batteries are not being charged past 12.7 v and as soon as I shut the engine off the low voltage alarm goes off. I can get the truck jump started and it drives just fine, at idle the oil pressure drops but when I put a load on the engine it picks up to normal.
I thought the alternator was causing this by not charging batteries up, after swapping for a good alternator the problem is still there, voltage drops to 10.0 v right after truck is shut off.
Tomorrow I am getting new batteries.

These are the codes I have
Engine ECU:
Power supply, Data erratic, Active
MID 128 SID 251 FMI 2
SID 146, Electrical fault, Active
MID 128 SID 146 FMI 5 my egr valve is unhooked and I know that is the reason for this specific code
SID 146, Electrical Fault, Inactive
MID 128 SID 146 FMI 3
SID 146, Electrical Fault, Inactive
MID 128 SID 146 FMI 4

Brake ECU:
SAE J1939 data link, Communication error, Inactive
MID 136 SID 231 FMI 9

Info Display:
Vehicle speed, Communication error, Inactive
MID 140 PID 84 FMI 9
Engine Speed, Communication error, Inactive
MID 140 PID 190 FMI 9
Engine oil pressure, Communication error, Inactive
MID 140 PID 100 FMI 9
Boost pressure, Communication error, Inactive
MID 140 PID 102 FMI 9
Engine coolant temperature, Communication error, Inactive
Mid 140 PID 110 FMI 9
SAE J1939 data link, Data erratic, Inactive
MID 140 SID 231 FMI 2
SAE J1708/1587 data link, Component failure, Inactive
MID 140 SID 250 FMI 12

Vehicle ECU:
SAE J1939 data link, data erratic, Inactive
MID 144 SID 231 FMI 2
PSID 230, Electrical fault, Inactive
MID 144 PSID 230 FMI 4
PSID 230, Electrical fault, Inactive
MID 144 PSID 230 FMI 5

Climate Unit:
Stepper motor. Air distribution, Electrical fault, Inactive
MID 146 SID 6 FMI 4
Stepper motor. Air mixture, Electrical fault, Inactive
MID 146 SID 9 FMI 4
Stepper motor phase 1, Electrical fault, Inactive
MID 146 SID 16 FMI 3
Stepper motor phase 2, Electrical fault, Inactive
MID 146 SID 17 FMI 3
Stepper motor phase 3, Electrical fault, Inactive
MID 146 SID 18 FMI 3
Stepper motor phase 4, Electrical fault, Inactive
MID 146 SID 19 FMI 3

Light Control Module:
SAE J1708/1587 data link, Data erratic, Inactive
MID 216 SID 250 FMI 2
Power supply, Ignition key in driving pos., Electrical fault, Inactive
MID 216 PSID 40 FMI 4
Brake lights right, Electrical fault, Inactive
MID 216 PSID 11 FMI5
Brake lights left, Electrical fault, Inactive
MID 216 PSID 10 FMI5
Side repeater left, Electrical fault, Inactive
MID 216 PSID 46 FMI 5
PSID 45, Electrical fault, Inactive
MID 216 PSID 45 FMI 5
Dir ind front L, Electrical fault, Inactive
MID 216 PSID 13 FMI 5
Dir ind front R, Electrical fault, Inactive
MID 216 PSID 14 FMI 5
Headlight high R, Electrical fault, Active
MID 216 PSID 3 FMI 5
Headlight high L, Electrical fault, Active
MID 216 PSID 1 FMI 5

If anybody has a clue what causes symptoms like this that would be highly appreciated.

 

Its a starter truck, just got new batteries. Haven't had a chance to do anything else. I just went through the starter wires and cleaned all contacts. I guess tomorrow I jump start the truck and let it run for a while than start checking wires to batteries. And I just put new fuses in.