DC to DC Chager - Worth It?

[traveldawg]

If I don't change the wiring from my truck's charging system to the input of a DC to DC charger and just rely on whatever wire gauge and amperage is available at the 7 pin connector (and into the RV) is it worth using a DC to DC Charger?

[jkwilson]

Yes, if you need the charging on the road.

The trick is that the only way to make a device take more current is to apply a higher voltage to it. With batteries, that means a higher voltage than the current battery state. A discharged battery trying to draw current from the charging system of the truck eventually reaches an equilibrium where the voltage drop in the truck and trailer wiring causes the voltage applied to the battery to fall so low that no more current will flow. This usually occurs well before the typical 15A limit of the circuit.

By installing a DC-DC converter, you are putting a device at the end of the wire that isn’t nearly as much affected by some voltage drop. It just needs power, so it draws as much power as is available from the truck at whatever voltage reaches it. Then, it boosts the voltage applied to the battery so as much power as is available flows into the battery.

[Scott'n'Wendy]

The stock setup charges lead acid fine to 100%. No DC-DC needed.
If you installed LiFeP04, then a DC-DC will charge your new battery to 100%, the stock setup won't. Going through factory original wiring, you don't want a big DC-DC charger because you don't want to go over about 8-10 amps. If you want to install your own charging wires...well...size the wires to the charge current you want to utilize.

[A.Texas.Yankee]

If I don't change the wiring from my truck's charging system to the input of a DC to DC charger and just rely on whatever wire gauge and amperage is available at the 7 pin connector (and into the RV) is it worth using a DC to DC Charger?

No. Unless you increase wire size from battery on tow vehicle to trailer, it will not be worth it. Adding a DC>DC charger doesn't magically create more amps. Your limiting factor will be wire size and fuses/electronic limiters in the truck. It'll will vary between model truck but you are likely limited to less than 10-15 amps regardless of dc>dc converter.

Full-time Traveling Family ,'21 Momentum 395MS-R, '21 F450 King, 2000watts solar, Dual Victron MP-II 12/3000 2 x 120v, 1220ah LiFePo4