Off grid help please

[Tom Cullen]

Hello,
Total newb here. A few quick questions if y'all would be so kind.

Our solar equipment.
4 100 watt 12v panels w/mc4 connections
1 40amp mppt controller
4 6volt 235 amp golf cart batteries
1 5300 watt dual fuel generator

Our situation.
Off grid 5th wheel

Our problem.
My batteries are hooked up to the 12 volt inverter preinstalled on our trailer. This runs only 12v appliances.
On shore power, we can run the 110.
Shore power can be either 50 amp or 30amp.
I currently run the generator about two hours a day to charge the batteries, and when I need 110 power.
Our solar is not yet hooked up because I am not sure about the wire gauge I need to use from the panels to the controller. And because the only good source of light is almost 40 feet from my trailer.

Additionally, we were recently gifted 18 225 watt 48v panels. I saw that Growatt has a 48v all in one 50amp inverter that I think was 4000 watts.
Can anyone tell me if I could hook up those panels and then run a 50amp connection straight to my shore power on the rv? It sounds doable, but I'm clueless. That Growatt is $1500 but it seems a small price to pay to upgrade our system 10 fold.

Any ideas would be greatly appreciated.

 

[RobertGreen]

Please link the Growatt model that you're considering.
Those "48v" solar panels will not produce exactly 48v; that's often a nominal rating. Consider the VoltageOC rating of the panels, and then consider connecting them in series-parallel to match the solar input of the Growatt unit.

If you'll provide the model or specifications from the panels, and the model of the Growatt unit that you're considering, you'll receive a lot more help, I am sure.

 

[RobertGreen]

Also, just to let you know-- although some of the Growatt All-in-One units advertise that they can run without a battery (your current battery isn't compatible with a 48v inverter unless you add more batteries) These units don't perform very well at all when run straight from solar; they're really intended to use a battery.

 

[Tom Cullen]

Hello,
Total newb here. A few quick questions if y'all would be so kind.

Our solar equipment.
4 100 watt 12v panels w/mc4 connections
1 40amp mppt controller
4 6volt 235 amp golf cart batteries
1 5300 watt dual fuel generator

Our situation.
Off grid 5th wheel

Our problem.
My batteries are hooked up to the 12 volt inverter preinstalled on our trailer. This runs only 12v appliances.
On shore power, we can run the 110.
Shore power can be either 50 amp or 30amp.
I currently run the generator about two hours a day to charge the batteries, and when I need 110 power.
Our solar is not yet hooked up because I am not sure about the wire gauge I need to use from the panels to the controller. And because the only good source of light is almost 40 feet from my trailer.

Additionally, we were recently gifted 18 225 watt 48v panels. I saw that Growatt has a 48v all in one 50amp inverter that I think was 4000 watts.
Can anyone tell me if I could hook up those panels and then run a 50amp connection straight to my shore power on the rv? It sounds doable, but I'm clueless. That Growatt is $1500 but it seems a small price to pay to upgrade our system 10 fold.

Any ideas would be greatly appreciated.

Growatt 48V 6000T 6kW MPV (250V Solar Input) Split Phase 120V/240V output (50A at 120V ,25A at 240V) – more in Nov – Watts247.com

watts247.com

 

[RobertGreen]

That particular model of Growatt is not compatible with 120v input voltage from the grid or generator; it's 240v AC input only. You won't be able to use it to plug into normal RV shore power.

 

[RobertGreen]

So a few quick notes:
-If you want to run a 48v inverter (and 48v is normally the way to go if you need a high wattage inverter, like 4000+ watts), then you'll need a 48v battery to run it. This means adding more batteries to your current setup. Trying to run high wattage devices from a 12v system can be frustrating due to the very large currents involved.
-If you want to be able to charge from RV shore power plugs, then you want an All-in-one inverter or discrete AC charger which can handle a 120v input. I believe some of the Growatt units can do this, but not the ones which feature 120/240 output as far as I know.
- Your generator also may well be 120v only, and will have the same issue. Most (but not all) consumer generators in that power range are 120v only as far as I know

Feel free to check out the resources section on this site for some hints about load calculations and power audits.
The normal flow seems to be: figure out what your power needs are ---> decide on a system architecture that is most favorable (the system voltage, the battery type, etc) ----> start picking components that are compatible with each other and your needs

 

[Tom Cullen]

That particular model of Growatt is not compatible with 120v input voltage from the grid or generator; it's 240v AC input only. You won't be able to use it to plug into normal RV shore power.

I'm off grid. My generator supplies 240. I have another two batteries to give me 48v. The growatt I linked to has either 25amp or50 amp output. Maybe I'm misunderstanding the definition of output. My panels are only 225 watts but they are 48v. What am I missing?

 

[RobertGreen]

Oh, my mistake.
In that case, yes, if the generator can provide 240v then it can supply that growatt and the growatt can have it's output wired into a 50 amp RV shore power receptacle.

The panels will probably have to be connected in a series-parallel configuration. Although they are "48v", the voltage varies based on conditions, and so they must be arranged in a way which is compatible with the solar input of that Growatt unit. Notice the different specifications in the Inverter Output, Solar Charger, and AC Input sections on the specs for that unit. I have attached a picture. Normally you make series strings of panels at the highest voltage allowed by your charge controller. This allows you to save money and hassle by being able to use thinner conductors and smaller breakers/fuses for your solar panel array.

Also, just FYI, that unit can be found for a couple hundred dollars less at other suppliers such as https://shop.signaturesolar.us/products/6kw-48v-250vac-80a-off-grid-inverter-by-growatt
I have never done business with those folks, and I'm not endorsing them, but I imagine you can find reviews on this forum.

 

[RobertGreen]

The specifications on your panels will determine how they may be arranged and connected to the Growatt. Particularly, you'll need to consider the highest open circuit voltage that they will produce (the Voc) at the lowest temperature that your array will see.

 

[RobertGreen]

I'm off grid. My generator supplies 240. I have another two batteries to give me 48v. The growatt I linked to has either 25amp or50 amp output. Maybe I'm misunderstanding the definition of output. My panels are only 225 watts but they are 48v. What am I missing?

Also, the reason that growatt says it has either 25 amp or 50 amp output is because it's 25 amps at 240v or 50A at 120v. The power output is basically the same either way.

 

[12VoltInstalls]

Any ideas

So your RV is a stationary application?

4000W of panel is robust.
If the RV doesn’t travel it would seem to me that I’d kill the onboard inverter/converter whatever it is and rewire for the full benefit of your solar array. In your situation probably a separate 48>12V converter makes sense. Although I prefer redundancy to have full 12VDC and 120VAC available simultaneously and you do have the existing equipment you may choose that as well.

Basically I think your current solar is totally not practical to make a part of the new panels and AIO. Battery-wise this is a place where lifepo can make sense, and your current battery bank would be undersized during sundown hours if you are using the power at full-bump. Alternatively, you could use lead acid batteries but have more all new ones that exceed the load to never get deeply discharged but lifepo may be a 15-year life in operation you prefer.

Just my thoughts.

 

[Tom Cullen]

I'm off grid. My generator supplies 240. I have another two batteries to give me 48v. The growatt I linked to has either 25amp or50 amp output. Maybe I'm misunderstanding the definition of output. My panels are only 225 watts but they are 48v. What am I missing?

Oh, my mistake.
In that case, yes, if the generator can provide 240v then it can supply that growatt and the growatt can have it's output wired into a 50 amp RV shore power receptacle.

The panels will probably have to be connected in a series-parallel configuration. Although they are "48v", the voltage varies based on conditions, and so they must be arranged in a way which is compatible with the solar input of that Growatt unit. Notice the different specifications in the Inverter Output, Solar Charger, and AC Input sections on the specs for that unit. I have attached a picture. Normally you make series strings of panels at the highest voltage allowed by your charge controller. This allows you to save money and hassle by being able to use thinner conductors and smaller breakers/fuses for your solar panel array.

Also, just FYI, that unit can be found for a couple hundred dollars less at other suppliers such as https://shop.signaturesolar.us/products/6kw-48v-250vac-80a-off-grid-inverter-by-growatt
I have never done business with those folks, and I'm not endorsing them, but I imagine you can find reviews on this forum.

Thanks for the info and the link. Solar makes my head hurt.

 

[Tom Cullen]

So your RV is a stationary application?

4000W of panel is robust.
If the RV doesn’t travel it would seem to me that I’d kill the onboard inverter/converter whatever it is and rewire for the full benefit of your solar array. In your situation probably a separate 48>12V converter makes sense. Although I prefer redundancy to have full 12VDC and 120VAC available simultaneously and you do have the existing equipment you may choose that as well.

Basically I think your current solar is totally not practical to make a part of the new panels and AIO. Battery-wise this is a place where lifepo can make sense, and your current battery bank would be undersized during sundown hours if you are using the power at full-bump. Alternatively, you could use lead acid batteries but have more all new ones that exceed the load to never get deeply discharged but lifepo may be a 15-year life in operation you prefer.

Just my thoughts.

Yes, we are building onto it, but it's stationary. When plugged directly into the shore power our 110 works, that's why I want the growatt unit so I can hook it into the 50amp recepticle. My shore power currently charges my batteries. I would like to keep this configuration. Panels to growatt unit. Growatt to rv. Which charges my one big 48v. I probably I have this all wrong but that's how I imagined it. Like i said, total solar newb.

 

[12VoltInstalls]

shore power currently charges my batteries. I would like to keep this configuration

Are you sure?

Those RV converters are inefficient and most do nothing to condition batteries or even have the settings to do so.

Your SCC, even most ‘cheap’ ones will treat batteries properly for best output and long life.