Added a couple of more DC to DC charger options. The first are the Victron Orion-Tr Smart DC-DC Chargers.
They support 12 to 12-30 amp, 12 to 24-15 amp, 24 to 24 - 17 amp non-isolated versions , they also have similar sizes and a couple of more like 12 to 12 -18 amps isolated versions.
The difference between isolated and non-isolated is if the grounds are tied together in the unit (non-isolated) or if the grounds are separated in the unit (isolated). For the most part in our environment the non-isolated version would be fine. If you have plans to measure current going into and out of the charger via shunts on the ground lines you would want the isolated versions.
All the units can be attached and viewed under you Victron connect app, you should note that it does not display current data to or from the unit. They all have automatic engine on detection, which can be disabled and also multiple remote on/off options.
you can also parallel multiple units together to increase the output. In this configuration it recommended that you disable engine on detection and use a remote option.
Another unit that has some promise is from Renogy the DCC50S 12V 50A DC-DC ON-BOARD BATTERY CHARGER WITH MPPT
. While I am usually not big fan on Renogy products. This unit has some features that peak my interest. While some others do this , the unit has an solar charger also. If solar is available the unit can share 50%/50% with the alternator while the engine is running. Remotes sense for accurate charge voltage levels, Another feature is that solar can be used to trickle charge the starting battery once the house is charged. Add in Renogy BT-2 Bluetooth adapter and you get a unit with some respectable features.