Freightliner Century problem with batteries

Are you sure you're reconnecting the cables and wires properly?

 

Confirm you're connecting the cables correctly. Then check for anything on the positive side touching the frame or any metal. Check for rubbed cables.

 

The starter could have an internal short.I had kind of similar problem too like when I turned my ignation on the starter would short and get stuck like that making a noise and it would get the thick neutral battery cable really hot.

 

You have a short to ground, that is probably unfused. Something in your positive side has a path back to the negative side.

 

I agree. Check your big stuff. Maybe the hot starter cable is chafed to frame possibly or some other flaw allowing the gremlins of electricity to flow at the volume you feel heat.

That's not a good thing. Those batteries need to be able to sleep, not feeding anything when truck is off.

 

Feel electrical items for heat or shoot them with an IR temp gun. Its literally possible for the whole cab or starter body etc etc to be acting as a resistive heat element.

You can pull fuses and relays one at a time and amp probe across the blades, or have someone watching battery volts for a rise, or even spark check the terminals each time you pull a new one (kinda crude way though)

Be sure your negative battery post shares a zero volt reference and continuity with all your major iron. Frame, cab, block, ground lugs etc. A testlight can help in a bind.. You want full glow or none.. A faint glow is pointing you in the right direction. Just snoop until you find something. Better your meter skills the faster youll get there.