Weird charging issues

So I had my truck die the other night after shutting it off and immediately trying to start it again. got a new battery and it ran but was at low volts then my volt gauge went out completely. Checked the voltage of each battery and all 3 including the one that i replaced were at a good 12.5 volts. turned the truck on to check if the alternator was working and it was charging but only the passenger side battery. Then after a bit i checked the volts again while running and now the passenger side battery was at 12 volts and the driver side battery was being charged. I have ordered all new battery cables for the truck since I am betting its a cable issue but I cant seem to find anyone having this problem. also every time i turn the truck on the volts read low on the gauge and if i drive within 5 minutes the voltage gauge goes out completely.

2004 cummins
297000 miles

 

Cables and ends sound like the issue. How old was the battery your replaced? They should be replaced in pairs. Now you have a battery that has been sulfateing and one not. Surface voltage only tells you part of the story. Amp draw tells the story better. Did you check voltage drop at each battery when starting? Charge each battery when disconnected from one another, let sit for at least 24 hrs and measure voltage drop from when charged. Hope with new cables, you get your issue resolved.

 

Temperature sensor under the driver's side battery can also act up, if that is broken/disconnected the gauge in the dash goes down to 12v and it dings. But alternatorn is still pushing normal voltage to the battery.