[AT] Cummins scan tool was OT Buck-Boost convertor for charging auxiliary battery

[James Peck]

That vocational truck was a Navistar with a Cummins engine. We had been told that we could use the cruise control setting to regulate PTO speed when stationary. The engine load was going to a shiftable transfer box that had pumps bolted to it. The Navistar dealer brought over a Cummins rep with a laptop type diagnostic tool.  We ended up adding a potentiometer that provided a voltage speed command to the engine in place of the fly by wire type accelerator pedal when the truck was stationary.

[James Peck] I worked on a 12 volt battery vocational truck that used voltage converters to get 24 vdc to run a plc and  electrohydraulic valves.

I personally would try to determine if the problem is just a poorly performing voltage converter. I would avoid modification if the problem can be rectified by replacing a poorly performing component.

]Cecil Bearden] To update the VC problem, after measuring the voltages and looking at diagrams again I am beginning to understand the system, but I don't understand the reasoning behind it.   In a nutshell, the alternator charges the main battery, at the same time the VC charges both batteries in series at 24V.  Definitely something lost in translation in their engineering. All I can think is What the H*#L ?!?!?!?
I have found a 24V alternator of the same size and connections.