I’d imagine the OP has now resolved his issue regarding the D250. However for the benefit of others with a similar dilemma. There would be no real issues integrating the CBE DS300 (or DSxxx) with a DC to DC charger.
To keep things simple you just need to disable the on board split charge relay. This is done by snipping R37 on the DS300.
The DS300 has not been without its issues over the years, and has undergone several upgrades where the onboard relays have been upgraded.
Importantly with any charging system of this type especially using non isolated chargers, earthing can be critical and where a lot fall over. Some owners choose to run additional large cross section cable direct from the alternator, as this can eliminate bad earthing between the alternator / engine and chassis. Attached you’ll find the drawing for wiring B2B chargers with CB180/DS300.
Regards Steve
https://www.12voltplanet.co.uk/user/downloads/Guide for fitting B2B charger with DS300 for vehicles with 'smart' alternators.pdf
