A member wiring an older small Lark trailer from scratch wanted help connecting a stand-alone 12V DC system that charges a 100Ah LiFePO4 trailer battery from the tow vehicle through a 7-pin setup and DC-DC charger, while keeping it separate from the existing shore power wiring. Members focused on the basic order of components, with the proposed layout being tow vehicle/junction box power and ground to the DC-DC charger, charger to battery, battery to cutoff switch, then shunt/monitor and...
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A member wiring an older small Lark trailer from scratch wanted help connecting a stand-alone 12V DC system that charges a 100Ah LiFePO4 trailer battery from the tow vehicle through a 7-pin setup and DC-DC charger, while keeping it separate from the existing shore power wiring. Members focused on the basic order of components, with the proposed layout being tow vehicle/junction box power and ground to the DC-DC charger, charger to battery, battery to cutoff switch, then shunt/monitor and fuse panel, with the charger’s ignition trigger wired as the manufacturer recommends so it only charges while the vehicle is running.
Members agreed the branch circuits and LED lighting approach were reasonable, and that wire color conventions vary in RVs as long as the wiring is kept consistent and identifiable. The main caution was fuse sizing: several members said the main fuse should protect the wire and be sized to the wire ampacity and expected camper load, not simply to the 100Ah battery rating, and that a 100 amp battery fuse sounded excessive for this small trailer. A 40 amp fuse on the tow vehicle/harness side and fusing for the DC-DC charger were discussed as reasonable if matched to the wiring and charger documentation, while the no-power issue when installing the 100 amp terminal fuse was suspected to be a faulty fuse or fuse holder. The topic ended with the general wiring plan accepted, but final testing and installation were still pending.