2023 Freightliner Issue - PLEASE HELP

2023 Freightliner Cascadia experiencing 13 to 13.6 volts constantly fluctuating at idle and drains to 9 volts instantly when engine is off. Parked for my 34 hour reset Thursday evening and began smelling Sulphur, hopped out and a battery was boiling with smoke spewing out. Took to shop this morning and literally just had batteries checked and one replaced a few hours ago at Love's. Problem isn't fixed...... Thinking alternator because I've been smelling a hot/burning smell after a long day of driving and it wasn't tested today when batteries were. What's weird though, the voltage goes up fine when started, so the alternator must be working right? It just instantly begins dying when turned off. What do y'all think? I'm a lease op so I desperately need help here. Just bought the new battery, was in a freightliner shop twice last week, and I'm getting a new trailer tire in the morning after a puncture. I'm not made of money and dispatch offers crap rates......

 

Probably need to replace all four batteries. Get them all tested.

 

They were all tested today, one was replaced. I assume that was the one that'd been boiling. No Sulphur smell now, but the voltage problem is still here and now worse. It's honestly scaring me. Don't know whether to keep digging the financial hole I'm in or walk away now.

 

You have something grounding out and draining the batteries. If the voltage shows normal with the truck running, then I dont see an issue with the alternator. Check the wires from the battery to the truck. Look good. you may have one chafed out contacting the frame. This is something that could burn the truck down,

 

2023? No Dealership support? Do you have an inverter? If so, Id disconnect it at the battery. See if that’s the problem.

 

Could be the starter. Could be anything. I guess you could find out by disconnecting it, and see if the gauge goes up, test the alternator the same way. Otherwise you probably need a shop diagnosis. Sounds like you just still have at least one bad battery in the bunch. 2023 is new. Doesn’t make sense.

 

Negative, no inverter. Bare bones truck, no apu, inverter, fridge, pr anything. All I have plugged in is a charger for a cigarette lighter plug to charge tablet and phones.

Truck has 60k miles and was doing great all week. Barely broken in I'd think.

 

You have something going on. When the truck is off and you see that much of a voltage drop. Something is pulling mass amounts of power. You most likely have a short in the system. Again, check the wires running from the batteries to the truck.

 

Gonna check first thing in the morning and report back to you guys. Hopefully it's nothing too bad or in a ridiculous spot to get to.

 

Could be a lot of things but you need to have the alternator tested. Bad diodes can cause the drain you are experiencing. A quick and easy test to rule out the alternator.