Multiple Use System, 24v or 48v?

[HomesteadDad]

I am looking for expert input on my situation. I am looking at building my first solar system and am trying to do it with an eye to the future.

My current needs are as follows:
I would like the system to be partially modular as I have two needs for it.
I have a school bus I am converting into a camper where the system will live the minority of it's life. I also have a pole barn where the power comes into my property and then goes from that panel to my house. The system will live most of it's life in the pole barn. I plan to have a permanent array on my bus and a separate array next to my pole barn. I want to buy one all in one inverter and one battery that can be moved from the barn to the bus when we travel. When we aren't traveling I plan to have the solar system run a refrigerator and two freezers while the sun is good, and have the grid power them when it isn't.

I have a line on used Trina 235 watt solar panels and plan on putting 4-6 on the bus and 6-8 in an array next to the barn to start. If I go with 24 volt, I am maxed out at 2000 watts input whereas if I go with 48 volt I believe I can look at 4000 watts.

I'm also thinking that if I choose to airbnb the bus regularly in the future I could keep the 48 volt all in one in the barn and buy a separate 24 volt for the bus to keep there.

I'm just thinking for future expandability I should go with 48 volt. Am I wrong? Thanks.

 

[DThames]

48v is normally the better option. An exception might be on a really small system where the smallest (normal) 48V battery would put the price higher than needed.

 

[HRTKD]

Moving a battery and inverter between locations sounds like a lot of work to me. When I decide to go camping, I hook up the truck to the trailer and go. No fooling around, I'm out of there.

I also have to wonder if you have to dumb down the system to work in the bus, which would reduce its effectiveness for the barn. I'm not saying it can't be done, just that I would go with two distinct systems.

 

[DThames]

Moving a battery and inverter between locations sounds like a lot of work to me. When I decide to go camping, I hook up the truck to the trailer and go. No fooling around, I'm out of there.

I also have to wonder if you have to dumb down the system to work in the bus, which would reduce its effectiveness for the barn. I'm not saying it can't be done, just that I would go with two distinct systems.

Maybe put everything in the bus and then plug it into the PV and AC for the barn, when parked. No AC for the barn when camping?

 

[12VoltInstalls]

I'm just thinking for future expandability I should go with 48 volt. Am I wrong? Thanks.

I think you’re trying to be frugal but you’re exchanging usefulness for impracticable imho.

At the panel limits you have imposed on yourself I’m assuming you are not using air conditioning. Big power is where the economy of 48V can be a benefit realized.

While I would tend to want a 12V but realistically you may get better use from the larger selection of 24V equipment available. You’ll just lose the convenience of the 12V RV lights and stuff unless you step it down.

 

[chrisski]

Maybe put everything in the bus and then plug it into the PV and AC for the barn, when parked. No AC for the barn when camping?

I have a 30 amp cable i run from my 3000 watt inverter to Rv‘s shore power. It could easily be plugged into a receptacle on a building. Just don’t know how you take care of the grid tie the OP asks for.

To me, I would think grid tie being removed for a portable RVwould be not approved by permits.

 

[HomesteadDad]

I think you’re trying to be frugal but you’re exchanging usefulness for impracticable imho.

At the panel limits you have imposed on yourself I’m assuming you are not using air conditioning. Big power is where the economy of 48V can be a benefit realized.

While I would tend to want a 12V but realistically you may get better use from the larger selection of 24V equipment available. You’ll just lose the convenience of the 12V RV lights and stuff unless you step it down.

For ease of use, I am planning on using the all in one and having most everything be 120, not 12v.

Depending on funds, I could add more panels to the bus, but I doubt space would allow for me to exceed the 2000 watts that the 24v all in one allows.

I don't doubt that there is an element of putting frugalness before practicality, but for now, this will be the only system I will be getting for now so I am very likely trying to make a square peg fit a round hole to some degree.

 

[HomesteadDad]

I have a 30 amp cable i run from my 3000 watt inverter to Rv‘s shore power. It could easily be plugged into a receptacle on a building. Just don’t know how you take care of the grid tie the OP asks for.

To me, I would think grid tie being removed for a portable RVwould be not approved by permits.

I may have been unclear in my original post. I am not at this point looking for grid tie, but using the batteries and all in one to power things in our barn. When the batteries run down I will use the grid to recharge the batteries. I won't be pushing power back to the grid any time soon.

I was planning on running a 110 plug as shore power to recharge the system when necessary/when the campground has hookups. Would I be better off using a 30 amp plug and having a dog bone adapter?

 

[DerpsyDoodler]

Put the inverter in the bus, park the bus next to the barn. Install a 30A outlet on a transfer switch on the bus. Install a 30A inlet to feed an electrical panel in your barn. install a transfer switch to switch between your bus inlet and your grid in the barn.

Bus either feeds bus or barn
Barn either gets fed by bus or grid.

As for the ground mount array. Add solar inlets to the bus so that when youre parked, you can have the ground mount and the bus mount PV feeding power to your system.

When you're ready to go camping. Shut breakers, flip transfer switches, unplug 30A, unplug ground mount, flip breakers back on, and go have your adventure.

 

[12VoltInstalls]

Would I be better off using a 30 amp plug and having a dog bone adapter?

You def should use the 30A cable and plug.
To connect to a 15-20A outlet, a simple plug adapter is all that’s needed. Better, just install a box with the 30A outlet.

You will need a transfer switch in bus.

Dogbone is typically 50A to 30A