Merge 2 DC-Solar SCT20 trailer systems

RMPowell01

New Member
Joined
Feb 27, 2021
Messages
5
Need assistance in taking 2 trailer mounted PV systems and making 1, off trailer, Off-grid system for new cabin. I am not knowledgeable on Solar and would really like some assistance. If anyone is close to Salem Oregon and willing to assist physically or if they know of someone with knowledge in the area it would be appreciated.

I have not be able to locate a wiring diagram for the SCT20. Each trailer has ten 240/250 watt panels, one Midnight Solar classic 250 controller, two 510 amp-hour flooded 48 volt batteries. and two SMA 6048-US Inverters. Batteries may need to be replaced. Currently running EQ on both systems as both systems were dead on arrival.

I do not understand why there are two SMA inverters on each trailer when the SMA says each unit can handle 4kW to 100kW. How many will I need to use on a merged single system?

Will I need to use both Midnite controllers when I merge the systems or a larger single controller? The Midnight has a maximum output of 55 amps at 48V.

On trailer has a Kubota 11kW generator. It is my understanding that one of the SMA inverters controls and auto start feature for the generator. Does anyone know if this feature is providing power to the AC plug on the trailer or if it charging the battery bank?

I know this may be a dumb idea, but I am in the middle having purchase the units. I don't need criticism I need assistance in making it happen.

Example of my lack of knowledge: The following are from the Midnight Controller sizeing tool and I have zero idea what they mean or where to find the information.

VOC (Open Circuit Voltage)
VMP (Maximum Power Point Voltage)
ISC (Short Circuit Amperage)
IMP (Maximum Power Point Amperage)

Another Newbie
 

45North

Let it shine!
Joined
Jan 2, 2020
Messages
467
Location
Canada
Here's what I would do:
  • setup the trailers as-is at your cabin site and run them for a while 'till you figure out what you've got, what works and what needs to be replaced
  • do some research on solar - how it works and what you need (and what those terms you listed mean - important!)
  • study what you've got and how it works so you can make a wiring diagram
  • figure out what you need for your cabin's power needs so you can begin figuring out how to apply the stuff on the trailers
There are lots of knowledgeable people on here who can help you with your questions, but you have to take the lead.
Otherwise, I guess you're looking at hiring a pro.
 

RMPowell01

New Member
Joined
Feb 27, 2021
Messages
5
This is about what I plan to do as soon as I have the units working. Need to go check the specific gravity of the cells now that I have done and EQ. The SMA inverters say they are 10kw continuous at 120v: 212A and each trailer has two. Each is poweing a 50 amp 120/240 outlet. I am assuming and yes I know the risk, that the SMA is setting the maximum amperage at 50 amps. I will read this SMA manual, but right now is it possible to combine these two 50 map outlets into one 100 amp outlet? Then I could power a standard 100 amp 120 or 240 volt AC circuit box in the cabin?

An yes I would love to hire a Pro, but I am 71 and retired. DIY is a must.
 

Bentpirate

New Member
Joined
May 24, 2021
Messages
3
Hello RMP
Merging dc solar trailer outputs to get 100 amp feed to power off grid home is exactly what I need to do. I purchased trailer last week and transported to desert property. Removed wheels and pintle hitch. I hooked up one 50 amp feed and it works! So now I need to explore what will happen when I merge the lines, likely in a junction box. It’s all about the alternating current being in sinc. I’m talking to a electrician buddy and will get back to you. Vice Vic you figure something out.
I don’t see why one can’t hook the panel together early in the system, before the Sunny Island.
 

RMPowell01

New Member
Joined
Feb 27, 2021
Messages
5
Bentpirate

I have gotten the units working, I have two. I had to replace two batteries that were dry as I could not get them to acceptable specific gravity levels. Currently I am about 30 days away from being ready to connect the two 50 amp outputs to one 100 amp ac circuit box. I have not been able to get any replies to this post from anyone that has been able to advise me and I have not been able to get anyone that works at installing the Sunny Island inverters to reply to my requests for paid assistance or on the Sunny Island blogs. If I find or receive any good information I will forward to you.
 

SalckwareRobert

New Member
Joined
May 28, 2020
Messages
35
The brochure says they can be paralleled. You want to find the manual and make sure it doesn't require a communication board to achieve it first, and how you hook up multiple units. They will have to talk in a master slave mode to coordinate output.
On the back of the solar panels will be a label with that info. What they mean is all over the place.
The reason could be a voltage or amp goes over it's specifications. Matching the system inputs to maximum is very difficult depending how the solar panels are hooked to each other.
Looks like it uses sunny boys to control the panels input, and the SMA is a clearing house for all the inputs including the sonny boys.

But 10 panels, that is one long trailer ...
 

RMPowell01

New Member
Joined
Feb 27, 2021
Messages
5
The brochure says they can be paralleled. You want to find the manual and make sure it doesn't require a communication board to achieve it first, and how you hook up multiple units. They will have to talk in a master slave mode to coordinate output.
On the back of the solar panels will be a label with that info. What they mean is all over the place.
The reason could be a voltage or amp goes over it's specifications. Matching the system inputs to maximum is very difficult depending how the solar panels are hooked to each other.
Looks like it uses sunny boys to control the panels input, and the SMA is a clearing house for all the inputs including the sonny boys.

But 10 panels, that is one long trailer ...
Perhaps I should try again with Sunny boys support. I have the Sunny Boy inverter manual. I will do some more reading this weekend and try to determine if a communication board is required. I lot of what I read is a bit over my head, but do understand more now than I did 3 months ago.

I really could benefit with some paid for assistance. For example I would like to add 5 more PV's to each bank of 5 that is going into the Midnight Classic 250 controller, and then thru the Sunny Boy inverters. The additional 5 PV's per bank would be added to the roof of a shipping container and connected to the individual PV banks on the DC solar trailer. My reason is to increase the recharge rate in the months where I only average about 3 solar hours per day.

Thank you very much for the reply and assistance.
 

Bentpirate

New Member
Joined
May 24, 2021
Messages
3
Bentpirate

I have gotten the units working, I have two. I had to replace two batteries that were dry as I could not get them to acceptable specific gravity levels. Currently I am about 30 days away from being ready to connect the two 50 amp outputs to one 100 amp ac circuit box. I have not been able to get any replies to this post from anyone that has been able to advise me and I have not been able to get anyone that works at installing the Sunny Island inverters to reply to my requests for paid assistance or on the Sunny Island blogs. If I find or receive any good information I will forward to you.
 

ghostwriter66

"Here - Hold my Beer"
Joined
Nov 13, 2019
Messages
1,663
Location
From LA -work in South Texas/New Mexico region
Need assistance in taking 2 trailer mounted PV systems and making 1, off trailer, Off-grid system for new cabin. I am not knowledgeable on Solar and would really like some assistance. If anyone is close to Salem Oregon and willing to assist physically or if they know of someone with knowledge in the area it would be appreciated.

I have not be able to locate a wiring diagram for the SCT20. Each trailer has ten 240/250 watt panels, one Midnight Solar classic 250 controller, two 510 amp-hour flooded 48 volt batteries. and two SMA 6048-US Inverters. Batteries may need to be replaced. Currently running EQ on both systems as both systems were dead on arrival.

I do not understand why there are two SMA inverters on each trailer when the SMA says each unit can handle 4kW to 100kW. How many will I need to use on a merged single system?

Will I need to use both Midnite controllers when I merge the systems or a larger single controller? The Midnight has a maximum output of 55 amps at 48V.

On trailer has a Kubota 11kW generator. It is my understanding that one of the SMA inverters controls and auto start feature for the generator. Does anyone know if this feature is providing power to the AC plug on the trailer or if it charging the battery bank?

I know this may be a dumb idea, but I am in the middle having purchase the units. I don't need criticism I need assistance in making it happen.

Example of my lack of knowledge: The following are from the Midnight Controller sizeing tool and I have zero idea what they mean or where to find the information.

VOC (Open Circuit Voltage)
VMP (Maximum Power Point Voltage)
ISC (Short Circuit Amperage)
IMP (Maximum Power Point Amperage)

Another Newbie

Can anyone tell me the size of the WHEEL (not tire) .. but wheel that this has .... we know its a 6 lug 15" but cannot find if its 5 or 5.5 or 6 on centre .... one of our contractors has this trailer and it blew out a tire but we need to send him both tire and wheel since he is 100 miles from civilization ... thx ...
 

Captain Voltage

Be the solution
Joined
Aug 21, 2021
Messages
3
Location
San Diego
Perhaps I should try again with Sunny boys support. I have the Sunny Boy inverter manual. I will do some more reading this weekend and try to determine if a communication board is required. I lot of what I read is a bit over my head, but do understand more now than I did 3 months ago.

I really could benefit with some paid for assistance. For example I would like to add 5 more PV's to each bank of 5 that is going into the Midnight Classic 250 controller, and then thru the Sunny Boy inverters. The additional 5 PV's per bank would be added to the roof of a shipping container and connected to the individual PV banks on the DC solar trailer. My reason is to increase the recharge rate in the months where I only average about 3 solar hours per day.

Thank you very much for the reply and assistance.
I’m a solar contractor here in San Diego and I have a customer that purchased one of the DC Power trailers.. Once I understand the configuration I will be able to help you expand or join together systems.. First of all I would tell you that when you add more solar you’ll need to keep it balanced.. Adding the same number of panels to each side.. Looks to me that there is (2) separate PV inputs that run into the charge controller.. We want to maximize and equally balance the input..
Have anyone found a single line yet or made one?
I will post one when I get it figured out..
 
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