Bluetti vehicle charging

Hi everybody. I have 700w of solar panel on the roof of my van, which nicely keep the AC200 topped up providing it’s not to grey and overcast! Anyway, the issue I’ve had is not being able to successfully bring the unit back up to a usable state of charge on a journey of 2 hours or so in the morning when being supplied from the installed solar panels.
I have a fridge running permanently and like to boil an urn during the journey so that we can make a hot drink when I arrive at my destination.

To overcome this issue i searched the internet and purchased a Battery to Battery Charger (BB) made by Sterling Power (Sterling part number 124870) which delivers an output of 48v at a maximum of 70A. (The output voltage can be adjusted to 58.8v).

When the connected to the vehicle battery, which is new and has a smart alternator, (Euro 6) it will deliver 58.8v to the solar input at around 650w. This is really useful and will also charge when the engine is idling too!

The default parameters of the BB charger require changing in order to set it up this way but never-the-less is very ‘doable’ & works well.
The only issue is that I have to physically unplug the solar panel connection to plug in the supply from the BB charger as required. I have briefly tried putting the BB input to the mains brick charger input, but this indicates an overcurrent fault, and so I don’t use this.
Does anybody know a way to connect both the solar and BB inputs together so I don’t have to keep swapping over input plugs to the AC200.

Incidentally I do know that there is the D050S enhancer which will probably do the job, and I’m awaiting delivery of this unit (not available in the UK yet!!).

Thank you in advance