4 new batteries and an inverter problems?

Have not seen but you need to run your motor while using your inverter, dont let the batteries carry the load of the inverter, let your alternator do its job, and the batteries are more of a buffer.

 

FYI: That product is only a 150 watt inverter when plugged into a cigarette lighter. That's the "smart" part.

 

This means absolutely nothing, we are diagnosing NOW, not 6 months ago

 

105 minutes without issue.
The inverter is a company issue, so must be approved for install, likely has to be approved by the truck manufacturer for warranty purposes too.
The company has the instructions for install, not TA. I'd ask your company tech for a diagram of how the inverter wires are supposed to be, or stop in on the tech for a quick look at it.

 

Parasitic draw. Voltage wouldn't just jump like that unless something switch off. Got a fridge? Big radio with a fan? Inverter with a fan? ELD just booting up?

I'm not sure you even have a problem with the truck itself. When I was a company driver I had to use a cigarette lighter inverter to power my laptop. I couldn't leave it on overnight or I'd get a low voltage alarm before morning. If your brick is rated at 90 watts that is the power it is delivering, not what it is consuming. The power consumption will be higher than that.

 

Yea Heartland does that crap also. I can park chock the tires, leave the park brake off and idle