When you put in a 24v system you now need adapters to handle both 12v output and 12v input. That right there adds cost for the adapters (converters, chargers, whatever you want to call them), cost for the wires, lugs, heat shrink, etc.
would I not be only transferring 24v to 12v once to power the 12v system in the trailer? I wouldnt need a converter for each item? A 40amp 24-12v converter on amazon is $60. wouldn't the only thing inputting power back to the battery be the solar charge controller and a shore power charger?
Since you do not have a generator, I'll assume you don't have a fifth wheel trailer. The landing gear and leveling systems in a fifth wheel have very high amp loads. A travel trailer may have a powered tongue jack. My tongue jack has a rated 25 amp draw. Your 24v-12v buck converter needs to be rated for
at least that amount. With wiring distance from the LiFePO4 battery to the tongue jack the amp draw may be even higher.
It is indeed a travel trailer, not a fifth wheel. In regards to the power tongue jack I do have one and it is also a 25A draw. The tongue jack is only about 6 feet away from where the battery, and system will be located.
That buck converter isn't 100% efficient so you have to take that into account. It also has a standby draw. It isn't much, but over time, it could draw down your LiFePO4 battery bank. But you say you'll put in a switch to turn off the buck converter when it isn't needed? Fine, more complexity, more wiring, more work, more expense. Oh, and you'll need to instruct everyone that uses the trailer on what that not so little switch does. Don't forget that the switch needs to be rated for the same amps as the converter.
Luckily I am the only one who sets up the trailer. No requirement to have anyone else know the equipment, which is no change from now. I plan of having a kill switch which will isolate the Solar panels, charge controller and battery while the trailer is in storage. Wont have to worry about any phantom draws this way. the solar will keep the battery where it needs to be while not in use.
To charge the LiFePO4 battery bank from the tow vehicle, you'll need a 12v-24v DC-DC charger. The naysayers will point out that you'll need a DC-DC charger even in a straight 12v system and they are correct. However, you need a slightly more complicated DC-DC charger that most likely is more expensive because it's a boost converter to go from 12v to 24v.
I will not be charging the battery at all while connected to the tow vehicle. The solar will be the primary form of charging the battery bank. secondary would be while connected to shore power.
The same issue comes up with the AC-DC converter. You need a new one that supports a proper LiFePO4 charge profile, but you also need one that is 24v. Just for giggles, I compared two IOTA Engineering AC-DC chargers.
45amp 12v and
25amp 24v. Prices on Amazon are
$150 and
$225, respectively. I didn't look too hard, so those prices may not be good examples. But you get the idea.
Good point I will have to read about and research this more.
I have a Victron 100/50 MPPT solar charge controller connected to my 640 watts of solar on the roof of the RV. The controller can handle more watts if the system was 24v, but I don't have room on the roof for more panels. So it's a good fit for a 12v system.
I am going off memory in regards to the roof layout, as my trailer is still in storage. I for sure need exact measurements and I will do a google sketchup before finalizing that. I am about 98% certain I have room for 2. May even have room for 3. 2 in the very front and 1 in the back.
24v sounds sexy. The added complexity is not.
