New RV build in OC CA

[Rocketman]

My main issues with 12v is I may have to put my inverter like 6-7 cable feet away from the battery bank and at 12v and 3000watts I’m worried about that run at 4/0 getting hot/warm.

I used the OEM 4/0 wiring in my MotorHome to run my Multiplus 12/3000. It is at least 10 feet away - and maybe more - depends on how that wire was ran. I do have some voltage drop (more than I would like), but the 4/0 cables do not get warm - much less hot.

And I also max out the mppt at 12v at 1400watts so I’m losing like 300 watts of production.


At 12v my main issues is the starting the onan generator. It pulls like 100 amps @ 12v so I may need to have a 12v battery anyway just to deal with that draw. How ever infrequent that is cause I think with 1700 watts of solar I may never need it.

Your lithium cells can handle the inrush of the generator start - but will the two Bms’s be able to support the inrush? That is the research that needs done.

 

[Azguy82]

I would not put 4s of Voc 59.4v into a 250/100. That’s 238v before you start getting cold - as the panels get cold the Voc rises. You use Voc for max volts.

Just install the 2s2p and you will be fine. You might be able to use a Victron 150/100 mppt.

Will you tilt your panels?

When flat - panels will only max out “at noon in June”. Today and Yesterday (in December) my panels were flat (travel days) on my 600w array - the max I got was 323w & 333w.
The 2 days prior, I had tilted panels, and those days I maxed out my 100/30 mppt (415w).

My other array I got 75% of rated power 600w on 800w of panels. So even in December in Baja I can get up to 75% of rated panel power. (This is why I over paneled my arrays).

I used the OEM 4/0 wiring in my MotorHome to run my Multiplus 12/3000. It is at least 10 feet away - and maybe more - depends on how that wire was ran. I do have some voltage drop (more than I would like), but the 4/0 cables do not get warm - much less hot.

Your lithium cells can handle the inrush of the generator start - but will the two Bms’s be able to support the inrush? That is the research that needs done.

I have a jk bms 200amp. So I will be fine there. It’s only if I go 24v on the battery bank that I need a different 12v source to handle the 100amp inrush of the generator and the campers 12v systems. The 24v to 12v victron dc-dc converter can only handle 70 amps. So I can’t use that. I’ve read that you can daisy chain them. So that’s an option. Or I’d have to get a sep 12v battery and get a dc-dc charger and have a separate 12v system.


It’s a pain either way. If I stay 12v I can only get 1400 watts out of my solar and I’m limited by the charge controller 250/100. I can add a second one but then I have to run new copper through the walls and roof when it already had 10awg from the factory. So staying 12v isn’t just about the 4/0 to the inverter. It’s just one of the issues.

Theres no perfect way to do it. Everything causes an issue. It’s just about which one is less of a problem.

 

[Reed Cole]

. The 24v to 12v victron dc-dc converter can only handle 70 amps. So I can’t use that. I’ve read that you can daisy chain them. So that’s an option. Or I’d have to get a sep 12v battery and get a dc-dc charger and have a separate 12v system.

You can probably keep a small lead acid starter battery charged off of the 24v-12v converter, or from the truck's alternator.

 

[Rocketman]

Because of the flat panels, I really doubt you will max out the 250/100 mppt very often. In RV’s it is better to be over paneled a bit anyway. So don’t worry about missing those couple of hundred watts - they are only good if the battery is not full. With 1680w as long as you are in the sun, your batteries will be fine.

I just realized your array is exactly 2x my big array. I have 800w of solar going into a 100/50 mppt. That mppt can only do 700w. I have seen 700w only a few times - three in three years. (I could have more - but I never tilt my panels in the summer & I seldom watch my CCGX). These were all in either June or July and always between noon and 2pm. (With daylight time “high noon” is 1pm). Most of the time the panels daily high is in the 600’s.

Do setup your array as 2s2p, that way if you get shade on one part of the panels, the sunny ones are going full tilt, and the shaded ones still produce a little.

 

[Scott SD]

I vote for 24v. I just finished the install on my toy hauler with 1460w of panels on the roof, but I have 3 mppts, 2 100/30s, and a 75/15 (aka “the workhorse”). I used 2/0 wire and the 24/12/70 step down converter to the factory panel. Everything works great. I only carry an 800w generator, but did not need it for our last 4 day trip to the desert. Used the microwave and the AC occasionally. I don’t want to haul around a heavy generator. Isn’t this a truck camper, why do you need an Onan w auto start?

 

[Azguy82]

I vote for 24v. I just finished the install on my toy hauler with 1460w of panels on the roof, but I have 3 mppts, 2 100/30s, and a 75/15 (aka “the workhorse”). I used 2/0 wire and the 24/12/70 step down converter to the factory panel. Everything works great. I only carry an 800w generator, but did not need it for our last 4 day trip to the desert. Used the microwave and the AC occasionally. I don’t want to haul around a heavy generator. Isn’t this a truck camper, why do you need an Onan w auto start?

The camper has a built in genny so if it’s there I wanna be able to use it if I need it. And yeah it’s a truck camper