Advice needed on a Hybrid Inverter for a Solar Trailer

[RememberTheMagic]

What I am trying to do is make a Solar Trailer that will be used on a small construction site (or to power a small log cabin home) where there is no grid available. The idea is to use a PV array that is mounted on the trailer along with the onboard Battery on the trailer to power the load(s).

Looking for 240/120 USA Split Phase

In this application I want it to use the onboard PV Solar array as the primary source, and the onboard Battery (when solar is not enough, dark outside, cloudy days, etc..), or better yet PV Solar Panels and Battery at the same time; HOWEVER when the trailer is not being used for the OFF GRID scenario, I want to be able to take the trailer home and plug it into the grid. In this scenario I want it to use the PV Solar Array only. Effectively at this point, the Solar Trailer becomes a ground-mount PV array.

I heard Growatt and MPP has such a solution but I can’t seem to get a straight answer on either. I would like to budget less than $2,500 on the inverter so that rules out SolArk, etc..

I am not married to Growatt or MPP, they are typically just a cost-effective product. Worse on either of those manufacturers I can't determine what model would work, if any.

I am going to use my own battery pack (and Charger) so that I don’t have to spend thousands on what most manufacturers want for their battery Packs. I have a Midnite MPPT Charge Controller, a Daly BMS and a 16-cell LifePo4 Prismatic Cells already working together as a pack that has proven to be reliable.

Any help is greatly appreciated, I am trying to get this done in the next 2 weeks, anyone got a solution? Used or New, make, model =o)


Update 4/2/2024 - Finally Finished the trailer!

Day one...
Finished - deployed







Looking to move forward ASAP

 

[peakbagger]

Unless you want to reinvent the wheel, take look at the DC Solar Trailers that are still floating around after the bankrupcy auction. The asking prices is generally far less than what the parts are worth.

One caveat is in most cases, you cannot legally connect a portable solar system into the grid. The equipment may be entirely capable to do so but generally power companies that call the shots want a permanently installed system.

 

[MichaelK]

First, I'd suggest taking a step back and start with a plan of what you need to power before you actually start to assemble a system. You want split-phase 120/240V? Why? What 240V tools are you expecting to power? Normally, 240V is reserved to big-ticket items like kitchen stoves, hot-water heaters, and central air. A mobile 240V system is not really ideal. A good general rule of thumb is that the solar you need to reliably power a load should be 2X the size of the load. A load like a 5000W air-conditioner is not likely to be successfully powered via a smaller system mounted on a trailer.

 

[timselectric]

HOWEVER when the trailer is not being used for the OFF GRID scenario, I want to be able to take the trailer home and plug it into the grid. In this scenario I want it to use the PV Solar Array only. Effectively at this point, the Solar Trailer becomes a ground-mount PV array.

What do you want it to do, when plugged into the grid? Charge the battery? Power some loads? Export to the grid?

 

[RememberTheMagic]

First, I'd suggest taking a step back and start with a plan of what you need to power before you actually start to assemble a system. You want split-phase 120/240V? Why? What 240V tools are you expecting to power? Normally, 240V is reserved to big-ticket items like kitchen stoves, hot-water heaters, and central air. A mobile 240V system is not really ideal. A good general rule of thumb is that the solar you need to reliably power a load should be 2X the size of the load. A load like a 5000W air-conditioner is not likely to be successfully powered via a smaller system mounted on a trailer.

Table saw onsite we use a lot, its 240. System will be 6kw with more than enough power to run the saw even with the inrush current.

 

[RememberTheMagic]

What do you want it to do, when plugged into the grid? Charge the battery? Power some loads? Export to the grid?

When plugged into the grid I want to sell power back to the grid, I am setup for that now and have 24kw in ground-mounted panels, so this would just supplement that when the trailer is at home.

 

[RememberTheMagic]

First, I'd suggest taking a step back and start with a plan of what you need to power before you actually start to assemble a system. You want split-phase 120/240V? Why? What 240V tools are you expecting to power? Normally, 240V is reserved to big-ticket items like kitchen stoves, hot-water heaters, and central air. A mobile 240V system is not really ideal. A good general rule of thumb is that the solar you need to reliably power a load should be 2X the size of the load. A load like a 5000W air-conditioner is not likely to be successfully powered via a smaller system mounted on a trailer.

Table saw onsite we use a lot, its 240. System will be 6kw with more than enough power to run the saw even with the inrush current.

 

[RememberTheMagic]

Unless you want to reinvent the wheel, take look at the DC Solar Trailers that are still floating around after the bankrupcy auction. The asking prices is generally far less than what the parts are worth.

One caveat is in most cases, you cannot legally connect a portable solar system into the grid. The equipment may be entirely capable to do so but generally power companies that call the shots want a permanently installed system.

Would love to get one, assuming I can get it for around the same cost. I can build one for around 10K

 

[MichaelK]

Table saw onsite we use a lot, its 240. System will be 6kw with more than enough power to run the saw even with the inrush current.

OK, looking on the web, I see 240VAC saws running on between 14A and 23A at 240V. The 14A saw is running at 3360W, so applying the 2X rule I usually like to mention, a system in the 6000W range is doable, though "mobile" is the real question. Suppose you build this with standard high-voltage residential grid-tie panels, in the 250W range? Plenty of those on sale on Craigslist relatively cheaply right now.

For 6000W, that would be 24 panels, that are ~a standardized size of 1 meter in width, or ~39". That works out to be a single row of panels measuring 39" X 24 panels = 936", or 78'. Doubling them up into two rows of 12, means 39', and three rows would be 26'. Looking at the long axis, assuming these panels are at least 65" long, that's three rows that amounts to 195" of vertical string; that a 16.25' string of panels. So basically a trailer at least 30 feet long with a string rising 10 vertical feet above the trailer framing. That's huge! I don't want to try to figure out how sturdy something that big will have to be to be safe to drive at highway speeds.

What might be more doable is divide the panels amongst two trailers, I suppose you can even call them the slave and master trailers. I could envision two trailers with 12 panels each, with two battery banks, and two sets of electronics. Each solar trail alone would be capable of 120VAC, but paralleling them for 240V is possible. Outback's 3648 inverter is one that can be paralleled as described, and can handle the inrush surges of big saw motors like what you are describing. Two rows of residential grid-ties would be ~20 feet long, and maybe about 6 vertical feet above the trailer frame depending on your optimal solar angle for your location.

 

[RememberTheMagic]

OK, looking on the web, I see 240VAC saws running on between 14A and 23A at 240V. The 14A saw is running at 3360W, so applying the 2X rule I usually like to mention, a system in the 6000W range is doable, though "mobile" is the real question. Suppose you build this with standard high-voltage residential grid-tie panels, in the 250W range? Plenty of those on sale on Craigslist relatively cheaply right now.

So it will have 8 PV Panels 435 watts each. Commercial Panels

For 6000W, that would be 24 panels, that are ~a standardized size of 1 meter in width, or ~39". That works out to be a single row of panels measuring 39" X 24 panels = 936", or 78'. Doubling them up into two rows of 12, means 39', and three rows would be 26'. Looking at the long axis, assuming these panels are at least 65" long, that's three rows that amounts to 195" of vertical string; that a 16.25' string of panels. So basically a trailer at least 30 feet long with a string rising 10 vertical feet above the trailer framing. That's huge! I don't want to try to figure out how sturdy something that big will have to be to be safe to drive at highway speeds.

No it's 168" long actually, 4 panels per side, each side (i.e. each string) will be 435*4=1,740 watts Mounted in Portrait Mode. All I am looking to do is recharge the batteries, the batteries will power 95% of the load and the site is operational 3 days a week.

What might be more doable is divide the panels amongst two trailers, I suppose you can even call them the slave and master trailers. I could envision two trailers with 12 panels each, with two battery banks, and two sets of electronics. Each solar trail alone would be capable of 120VAC, but paralleling them for 240V is possible. Outback's 3648 inverter is one that can be paralleled as described, and can handle the inrush surges of big saw motors like what you are describing. Two rows of residential grid-ties would be ~20 feet long, and maybe about 6 vertical feet above the trailer frame depending on your optimal solar angle for your location.

 

[Hedges]

Would love to get one, assuming I can get it for around the same cost. I can build one for around 10K

Retail price of 2x SI-6048US is around $10k
But you can get on eBay for around half that.

The batteries are often in poor shape.
Included PV array is rather small for inverter capacity (takes a summer's day to provide 1 hour full load operation) and undersized for the lead-acid battery charging needs.

Trailer looks good if you want that much to be portable.
Total weight requires a larger pickup truck to tow.

 

[timselectric]

When plugged into the grid I want to sell power back to the grid, I am setup for that now and have 24kw in ground-mounted panels, so this would just supplement that when the trailer is at home.

An off grid AIO isn't capable of export. You need a hybrid AIO for what you want to do.

 

[RememberTheMagic]

An off grid AIO isn't capable of export. You need a hybrid AIO for what you want to do.

right, what make/model fits the bill?

 

[RememberTheMagic]

An off grid AIO isn't capable of export. You need a hybrid AIO for what you want to do.

correct, looking for a hybrid model that can do this

 

[timselectric]

Any hybrid AIO would fit the bill. I'm planning to add one to my system in the future. I'll probably go with a SunSink 16k. I prefer to use a transformer to get split-phase. So that the inverter sees a perfectly balanced load. And I can get it's full rated capacity.

Look for the hybrid AIO's in this section.

All-in-One Systems

diysolarforum.com

 

[RememberTheMagic]

Any hybrid AIO would fit the bill. I'm planning to add one to my system in the future. I'll probably go with a SunSink 16k. I prefer to use a transformer to get split-phase. So that the inverter sees a perfectly balanced load. And I can get it's full rated capacity.

Look for the hybrid AIO's in this section.

All-in-One Systems

diysolarforum.com

ouch ! that is $$$$$$$$$$ woo hoo...

 

[RememberTheMagic]

ok so it looks like I will just go off grid for now, with this solution, Later I will add an inverter that will just do grid tie.

 

[timselectric]

I'm not familiar with that inverter.
Does it not have a built-in SCC?

 

[RememberTheMagic]

I'm not familiar with that inverter.
Does it not have a built-in SCC?

it does, but I will not be using it, I will be using a Midnite SCC (labeled MPPT Charger in the image).

 

[timselectric]

Curious why.