DC-DC converting for 48V

DIY
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1

Like many others, I’m in the process of upgrading my motorhome’s solar system from 12V to 48V. This has created a quandary that I’m seeking to resolve, the DC-DC power transfer process. As manufactured, the motorhome has four power systems, the chassis(12VDC), the house(12VDC), the house(120VAC), and the battery-bank (12VDC). There are three power transfer processes in the motorhome: from the battery-bank to the house(12VDC), from the chassis(12V-alternator) to the battery-bank (12VDC), and from the battery-bank (12VDC) to the chassis(12VDC) – i.e., the “battery boost.” My goal is to preserve all of them in my conversion to the 48VDC battery-bank, if possible. The conduit between the house and the chassis are two (1 pos & 1 neg) 2 AWG (33 mm2) cables. Note that my use of the term “battery-bank” would include the batteries, inverter, fusing, etc.

  1. Battery-bank(48VDC) to the house(120VAC) – This will be accomplished by the Quattro inverter.

  2. Battery-bank(48VDC) to the house(12VDC) – This is where the first problem lies. There are two possible solutions that I know about. The first is to keep a small 12V battery, charged with an Orion XS 12-12/50 supplied with power from an Orion-TR 48-12/30. IMO – this solution would increase maintenance issues, as the battery would add a fifth power system. My idea is to use four Orion-TR 48/12-30 to supply the necessary power. The largest power user of the house(12VDC) is starting the generator (105A for 10 seconds). This solution would appear to reduce the maintenance issues, if I’m not missing something here (many people oppose this idea). Would the surge of starting the generator negatively harm the lifespan of the Orion-TR 48/12-30? Note: The generator would need to be started on a varying frequency: Not at all in the winter or summer months (in RV campground), and in an increasing frequency (from once a week to every day) during the spring and fall months. Other than the generator, the power usage would likely be less than 30 amps at any one time.

  3. Chassis(12VDC-alternator) to the battery-bank (48VDC) – This is another problem. I’ve heard two solutions: 1) Add a 48V alternator to the motorhome, and 2) Add an Orion-TR 12/48-8 (Would this work? Would this connect to the chassis-house conduit like the Orion-TR 48/12-30?). Does anyone have any other ideas?

  4. Battery-bank (48VDC) to the chassis(12VDC) – I think this would be solved with the solution for the battery-bank(48VDC) to the house(12VDC) system which feed the chassis battery, but I’d like your thoughts on this.