12v? 24v? 36...48v????
I'm very near to picking up a new travel trailer that I intend to pack with solar and LiFePO4 batteries. It's a 30A 120VAC RV. I understand the electrical wiring advantages of the higher DC voltage ...
Forum Discussion
StirCrazy wrote:afidel wrote:
Personally I'd run the 12V stepdown converter into a 12V battery, either lithium or SLA. That way peak loads for the slide motors and compressor motor get taken up by the 12V battery and the 12V converter can just top that off. I know there are folks that team a couple of 12V stepdowns together to supply the loads, but it has to be much more stressful on the components in them than if there was a decent pool of ampacity there. Since you aren't actually using it for storage capacity a 50Ah 100A LiFePO4 would work great and they're like $160.
The big advantage of 48V is you can use a much cheaper MPPT controller since they're basically priced on output amps and 48V is 4x lower amps for the same watts. Wiring costs are also much lower since you get to drop down to wire gauges which are commonly available instead of double 0 or triple 0 cables.
but thats like I said, keep the battery side all 12 volt and use a MPPT charger (more expensive by the way not cheeper) and stack the panels to 24v. you could probably spend a little more and get one that will handle a 48 volt input, but I don't know if it would be worth it for most people in a rv setting. the one problem you do run into with a all series run is shading.. in a home system where you have solar out in the open it isnt an issue, but for a lot of camping it is. I guess you would have to look at the price increase to a 48v input MPPT VS the upgraded wire size for the 24V setup. wiring is going to be an issue anyway you look at it with the size he wants to run so it will have to be resized.
edit, I did look at my brand and a MPPT charge that wil handle a 48V input is only 160.00 more canadian (one size biger) so it will be tight as to which way is cheeper, but I would go that way myself four 24V panels in a 48V series / parallel set up get the smaller wire size and you get some protection from shading.
What I was saying is that a 30A MPPT can put ~1,500W into a 48V system, to accomplish the same with a 12V battery system requires a 120A MPPT controller which are 3-4x the cost and several times the size and mass.
