12v? 24v? 36...48v????

afidel wrote:

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.

I haven't seen a 30amp mppt that will take a 48v input, but I am sure there are, my 40Amp will only take 24V input so if I want to add another panel to my camper which I am planing on I have to do parralell, or buy the 60amps controler which will take 48V of panel input, and that is only 100 bucks more than the 30 amp 24v one. so ya I get where you coming from, i just don't see that much of a price increase. my little 40amp will handle 1040 watts of 24V input, which to be frank is more than I will ever use in my little camper, but I will have to put them in paralell as it won't handle 48v haha, but my 5th wheel is getting upgraded to 12 to 1400watts of panels so if I get the 60amp verion of my mppt it will take 48V so I would still have to do a series/paralell setup using 24v panels and I'll just pull new wires down and mount the charger right at the batteries. but if there are reasonably priced 30amp 48v mppt controlers let me know that might be another way for me to go on the 5th wheel. doing 4 smaller 24v panels and still be around 1000watts and more efficient than that 480 watt pwm set up it has now lol. its funny I get more AH of charging from my 325 watt MPPT on my camper than I do on the 480 watt pwm on the 5th wheel in a day.