question

This will be because the IP65 charger on the start battery is raising the start battery voltage above the Orion's setting for turn-on voltage, and you definitely want to correct that since the Orion can pull more current from the start battery than the IP65 is delivering.

You can raise the Orion's turn-on voltage so it doesn't turn on until later, or lower the IP65's charge voltage to be lower than the Orion's turn-on voltage, or both, or pull the remote jumper from the Orion which will disable the behavior, or wire in a switch to the remote jumper so you can enable or disable it at will.

Trying to make this work automatically by adjusting various voltages probably won't prevent DC-DC operating at inappropriate times while sufficiently charging the starter battery.

A manual switch would work, but if want an automatic solution, you could wire the ignition switch to the remote terminals of the DC-DC. This will prevent it from turning on unless the engine is running.

Thanks for the replies. I also thought that turning off the dcdc charger would fix the issue, so a few days ago I did turn off the dcdc charger in the app (settings, battery settings, charger enabled = set to off) but after just a few days my starter battery was below 12 Volts meanwhile the ip65 charger was in float mode showing 0.0A?! So I re-enabled the dcdc charger. After a day or two the battery was fully charged again! I don't understand how turning off the dcdc charger could trick the trickle charger in thinking that the battery is full while something was discharging it??