Trailer batteries would not charge while towing with refrigerator on 12 volts
Problem: 2017 Chevy Silverado 1500 with variable voltage alternator
Computer on truck would reduce voltage output of alternator when start battery was charged fully charge for better fuel mileage
This would prevent trailer batteries to charge fully while the refrigerator is pulling 14 amps
The fix is adding a dc to dc charger at the trailer batteries using a redarc bcdc1240d charger

This charger boost the voltage from the start battery to 14 .5 max to charge the trailer batteries and is completely isolated from the truck charging system and is turned on and off by a trigger wire from the ignition circuit

My solar system is only set up for 2.5amps as a trickle charger for keeping batteries topped off while trailer is stored
The wiring from the start battery to the dc to dc charger at the trailer batteries is 35 feet of 4 awg using a 175amp Anderson plug and the trigger wire is 14 awg using the center pin on the 7 blade pigtail( no back up lights on my trailer) and adding few more ground wires on the trailer frame
This gives me 40amps of power going to my trailer batteries and the charger switches to float when trailer batteries are at 100%

Les, that's a pretty impressive solution to the trailer battery charging problem. 4 gauge wire is a hefty conduit! How much did all these mods cost you, if you don't mind me asking?

Edit: I just looked up the DC-DC charger, and see it can basically replace a solar controller, so that's another great way to give it power (and charge your battery) while camped!

- Jack

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Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH, Progressive Dynamics Converter, Fan-Tastic Fan, LiFePO4 battery 12V DC Electrical System, SoftStartRV mounted on A/C
2024 F150 Platinum FX4 3.5L PowerBoost SCrew

Yes on solar I tied my small solar panel to the dc to dc charger
4 gauge is what was required for the length for no voltage drop
The whole set up charger connectors and wiring only $800.00 plus my own labor

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Les & Patricia
2006 22ft towlite (replaces 97 21TL)
2006 Toyota tacoma pre-runner 4.0 L V-6 quad cab
w/ 98 chevy Powervision towing mirrors
2017 Chevy Silverado 1500 5.3 v8 (replaces Toyota)
2 Hobie mirage pedal drive kayaks