DC- Switching or connectors between two Solar Strings - RV <-> Solar Carport

[eXodus]

I got an RV with a 900W of Solar (2000w MPPT) and was thinking about building a Solar Carport (3-5kw) - to park the RV underneath.

What is a solar carport, and how much does it cost? - Understand Solar

While a normal carport provides covered shelter for a parked car, a solar carport provides power too! A feasible alternative to rooftop solar perhaps?

understandsolar.com

As soon as I get the RV parked I would like to switch to the stationery system.
Sure I could just have a few MC4 connectors dangling and changing over from the RV system.

I'm using the RV rather often - every 3-4 weeks. So those disconnects would wear out the connectors rather quick.
Alternative - just have a second or third MPPT in the RV and connect those inputs when under the solar cover?

Starting to collect requirements and ideas.

 

[timselectric]

Anything you do will require a connection being connected and disconnected. I would choose connectors with high cycle life. Maybe a magnetic connection.

 

[eXodus]

a connection being connected and disconnected.

yep, multiple times every year.
I was thinking about the Andersen connectors, since I might be looking at up to 30A, but those things are rather clunky.

Are there any DC wall outlets / sockets?

Living on 12 Volt - Part 2

I would like to have something simple like the RV Power Cord - I unplug it from the Generator Outlet in the Bay - and plug it into a pedestal. Takes like all of 30 seconds to switch from generator supply to grid power.

Similar in DC - unplug the RV-roof mounted system and plug into the carport mounted system

 

[timselectric]

If you can turn it off, before unplugging it, just about anything is fine. Just make sure that it's not something that is common. You wouldn't want someone plugging the wrong thing into it.

Disclaimer: I'm not recommending that you use anything that isn't rated for this use.

 

[eXodus]

I'm not recommending that you use anything that isn't rated for this use.

I can get DC Circuit Breaker to make sure that the panels are not producing any power when connecting or disconnecting.
DC-arks only good for welding

Any easy to use DC connector recommendation?

I found those 30A IP68 connector for Marine use:

SP21 Bulkhead IP68 Waterproof Plug & Socket Connector 500V/30A 3pin | eBay

SP21 2 3 4 5 7 9 12 PIN WATERPROOF CONNECTOR. 2pin, 3pin,4pin,5pin IP68 POWER CABLE AVIATION Screw Panel PLUG SOCKET. Rated Current (A): 30A. Typepower connector. Connector StyleSolder Free. Featureswith rubber ring, with location pin, direct plug with long end on both side.

www.ebay.com

 

[No Idea]

I can get DC Circuit Breaker to make sure that the panels are not producing any power when connecting or disconnecting.
DC-arks only good for welding

Any easy to use DC connector recommendation?

I found those 30A IP68 connector for Marine use:

SP21 Bulkhead IP68 Waterproof Plug & Socket Connector 500V/30A 3pin | eBay

SP21 2 3 4 5 7 9 12 PIN WATERPROOF CONNECTOR. 2pin, 3pin,4pin,5pin IP68 POWER CABLE AVIATION Screw Panel PLUG SOCKET. Rated Current (A): 30A. Typepower connector. Connector StyleSolder Free. Featureswith rubber ring, with location pin, direct plug with long end on both side.

www.ebay.com

I have those same IP68 connectors in the next size down version for a kayak battery box I built. They are OK but not very strong or thick plastic and the connectors are solder only. Mechanically they are pretty weak.

 

[No Idea]

I thought the MC4s would be OK because they are used for portable solar panels too which get plugged and unplugged a lot.

You could have a male - male and a female - female on the PV side and same on the RV side and replace those like sacrifical MC4s periodically and so the primary MC4s on the PV and RV are getting disconnected much more infrequently.

 

[eXodus]

I thought the MC4s would be OK because they are used for portable solar panels too which get plugged and unplugged a lot.

maybe I have to find some higher end MC4s
The few I got experience with tend to get stuck a lot. I got a pre-flight long checklist of items when I'm making the RV travel ready.

Don't want to add lengthy tasks to the list.

the connectors are solder only

Former electrical engineer here - what's wrong with soldering? The cable is not mechanically hold by it. It's only 30A

 

[No Idea]

I can't solder for sh*t hence worrying about my connectors but those IP68 ones you linked are labeled "aviation" in a very artistic license sense - they are cheap mass produced quality. Slippery to pull apart too. My fingers slid off and I accidentally pulled on the cable a couple of times.

Coincidentally another thread a couple weeks back was discussing how to make MC4s more waterproof for RV use in driving rain. Greasing them was discussed then not recommended in case they came apart too easy with vibration but in your case for static use that might be worth a try?

Bottom line is my only experienced input is that those blue and black IP68 ones are not good quality.

 

[eXodus]

Bottom line is my only experienced input is that those blue and black IP68 ones are not good quality.

Thanks for the experience, I'm going to do more googling. There must be a high amp easy to use DC IP68 connector somewhere in this world

MC4 are designed for installation of solar system and not really repetitive use.

 

[Rednecktek]

As soon as I get the RV parked I would like to switch to the stationery system.

So just a quick clarification here. You say you've got a 900w array on the RV already and you want to make a solar carport covered in panels that you plug into the RV when it's parked, right?

Are you only going to have 900-ish watts of power on the carport or do you need to think about overpowering the SCC in your RV by connecting it to a carport sized array?

I guess a super useful way to do it, if you've got the space and coverage anyways, is to just make a small shed in there with some batteries, an inverter, and wire the inverter to an RV plug on the outside. Drive up, plug in, power on, walk away.

Just a thought anyways.

 

[Rednecktek]

Lag double post

 

[timselectric]

I can get DC Circuit Breaker to make sure that the panels are not producing any power when connecting or disconnecting.
DC-arks only good for welding

Any easy to use DC connector recommendation?

I found those 30A IP68 connector for Marine use:

SP21 Bulkhead IP68 Waterproof Plug & Socket Connector 500V/30A 3pin | eBay

SP21 2 3 4 5 7 9 12 PIN WATERPROOF CONNECTOR. 2pin, 3pin,4pin,5pin IP68 POWER CABLE AVIATION Screw Panel PLUG SOCKET. Rated Current (A): 30A. Typepower connector. Connector StyleSolder Free. Featureswith rubber ring, with location pin, direct plug with long end on both side.

www.ebay.com

I think that those would fit the bill, nicely.

 

[eXodus]

Are you only going to have 900-ish watts of power on the carport or do you need to think about overpowering the SCC in your RV by connecting it to a carport sized array?

The carport is going to much larger - more in the 3-5KW range.

I will be absolute over paneling the SCC in the RV, it's good for only 2000W. So depending what I do I need to add a second MPPT.

I guess a super useful way to do it, if you've got the space and coverage anyways, is to just make a small shed in there with some batteries, an inverter, and wire the inverter to an RV plug on the outside. Drive up, plug in, power on, walk away.

I'm not fan of having equipment sitting around unused and potentially exposed to the elements. Florida is a tough climate for electric equipment to sit in unconditioned spaces.

Further all of the batteries will be inside the RV.

 

[Rednecktek]

I'm not fan of having equipment sitting around unused and potentially exposed to the elements. Florida is a tough climate for electric equipment to sit in unconditioned spaces.

Fair enough, it was just a noodle. It does make me want to do something similar at my camp some day since a lot of the friends of the family have travel trailers and I have a good spot for a 30ft carport out there with a southern view.

After the grid power, rebuilding the shower, current solar system, toilet replacement, septic system, lookout cabin on the bluff, second shed with laundromat and ATV storage... ?

 

[ArtDeco]

On a related note are inverters weatherproof (temperature proof?) enough to work in an exposed environment like a car port ? I only had my old inverters inside an attached garage, and would like to put it in a carport . Can an inverter and batteries be exposed to below freezing temps and snow drifts like under a ground mount?

 

[timselectric]

Yes
Some inverters are outdoor rated.
And some batteries have built-in heaters.

 

[HRTKD]

This situation isn't that much different than an RV that makes use of ground deployed panels. I have separate solar charge controllers for my roof array and my ground array. I flip the double pole circuit breaker - going into the ground solar charge controller - off before disconnecting my ground array. The breaker stays off until I have the array reconnected at the next boondocking site.

I'm using an SAE connector on the side of the trailer. It's good enough for my ground array, but would certainly not be acceptable for your carport array.

I have a 50 amp connector next to the SAE connector. Spec says it's rated to 500 Volts DC. If I expand my ground array I'll put in a similar connector and ditch the SAE connector.

 

[Hedges]

If inverter with battery supported AC coupling, you could have GT PV inverter on the parking structure and use an AC plug.

For DC pluggable connections I'm presently swapping strings between my single phase inverters and a 3-phase one.
Plan was to do this with MC3 cables (machined pins and no locking features) inside a disconnect switch (ensures open circuit when connectors are mated/unmated.)
For now, just doing that inside a junction box due to wire clutter and available space.

Guess what happens when you plug a 480V charged inverter capacitor bank backwards into a second inverter (with clamping diode)?
The plan to keep cable ends on a short leash, restricting mating options, hasn't been implemented yet either.

Anderson connectors could be an option for you. May be suitable voltage and current rating. Just think about how long an arc could be drawn and consider method to ensure circuit interrupted first.
In-line fast fuses may or may not be beneficial; they were in my case.