My SMA system install so far and precharge questions

[SilverbackMP]

Here’s some photos of my install so for.

First we have the panel mounts. It’s three separate Sinclair Skymounts 2.0 that will hold seventy two 375 watt panels with twelve each in series to produce just shy of 600v each string on an extremely cold/sunny day.



I split the mounts into three to try to keep things as level, plumb, and on grade as much as possible…although this did cost more.

Gonna split this posts into parts as my phone is low on power and I’d hate to have a huge write up and loose it.

 

[SilverbackMP]

We buried two runs of 2 inch inch conduit for future expansion. Schedule 80 for the first chunk where I might have tracked vehicles passing over.

 

[SilverbackMP]

 

[SilverbackMP]

The conduit goes to my solar shed and future mini server room.

This shed was originally built about 25 years ago by my parents originally to house a China Diesel genset (which was a POS).



They eventually switched to a Onan propane unit…which was a bigger POS.


Anyhow I digress.

Several years ago I got a decent price on that orange Ingersol 30kw unit (Cummins 4BT).

The only downside, it powers a 3500 watt Outback 12v inverter and cheap deep cycle FLA golf cart batteries inside my mom’s house. Huge waste of energy as they can only absorb a fraction of that output.

 

[SilverbackMP]

That shed was stuffed to the brim with crap and the siding had degraded with flying squirrels chewing holes in it and living inside.

I cleaned it out and had the sheriff serve the squirrels with an eviction notice.

We resided it, framed in windows, added blocking to hang a mini split, rewired existing interior wire, new gimbal puck lights, etc.

Framed over the concrete floor and then spray foam the entire thing.

I added additional Rockwool insulation more for fire blocking than insulation. Then all walls got 3/4 inch plywood shealthing that was then covered with 5/8 type x drywall.

The floor material is 1/4 inch rubber roll mat.

 

[SilverbackMP]

So from left to right is the battery storage cabinet. I have eight 16s batteries built from (well in the process of building) 230ah CALB cells along with M/S REC BMS units and 300 amp Blue Sea fuses. This cabinet could hold ten such batteries.

From the battery storage area, the DC power cables will travel to the 2000 amp midnight battery combiner box to the right and pass through 250 amp midnight solar breakers (the box has 12 such knockouts which is the reason I went with it rather than the 1000 amp version).

I figure if I need even more battery, I can fit a couple under the combiner box.

 

[SilverbackMP]

Then we have four Sunny Islands (two brand new ones, and two trailer take offs, I have a fifth spare one).



And then four 7.7 Sunny Boys. I’ll only be using three. One is a spare for right now but I might end up with six or seven with expansion.

The 200 amp circuit box will be the AC power distribution box…one line going to my mom’s house, one stubbed in for my future house, one going to my new shop (still in progress) and one stubbed out for a future building a bit bigger than the current shop.



The right side of the solar shed will also have two 10u short (20 inch) depth swing out sever racks for (probably) three NAS setups, network switches, etc. I’m dropping either 1.5 inch or 3/4 inch conduit in most trenches we have open to run 12 or 8 stands of SM fiber.

I will probably physically subnet POE cameras, IOT devices, and streaming (I.e. Plex) onto their own physical LAN (and probably create some VLANs within that for the cameras and synology).

Buisiness severs/NAS(s) in another subnet.

And if I don’t have enough juice to power two homes, a shop, a business barn, and various outbuildings? I guess I’ll be adding a second similar system in a few years (could probably add redundancy with various transfer switches too).

 

[SilverbackMP]

The one thing that I’m trying to wrap my head around…I’d the requirements for pre charging the Sunny Boys.

Maybe try to copy @MurphyGuy ’s setup from this thread?

My Push Button Pre-Charger Install for the SW 4024 Inverter

Wait - Is that mine our yours?! How did you take a picture inside my e-Panel?! ? Remotely enabling the camera in your smartphone. We're listening to you talk to yourself, too.

diysolarforum.com

Oh and thanks for all the resources. If it weren’t for the regular contributors, I’d be SOL trying to figure all of this out,

 

[SilverbackMP]

Working on top balancing my first battery now. Kinda hard with a 3500 watt inverter and crappy FLA batteries but I’m gaining on it. It I can get 2-3 batteries up and going, the panels hung, and the system commissioned, it would help a ton with top balancing the others.

I also have to top balance on my mom’s kitchen table as my shop has spray foam but no heating yet running besides a propane ventless and kerosene salamander (when I have my small genset running)…between them and six month old concrete, I’m having a ton of condensation.

 

[toms]

Looks great! Depending on what you are using to disconnect your batteries from the Sunny Islands, the REC pre charge module can work well.

 

[SilverbackMP]

Looks great! Depending on what you are using to disconnect your batteries from the Sunny Islands, the REC pre charge module can work well.

The main way will probably be the breakers in the combiner box….so I could turn on one at a time.

To physically disconnect them, they will have Anderson connectors and will be in boxes similar to the Digital Mermaid’s.

 

[toms]

The main way will probably be the breakers in the combiner box….so I could turn on one at a time.

To physically disconnect them, they will have Anderson connectors and will be in boxes similar to the Digital Mermaid’s.

You will need some way for the BMS to disconnect the batteries from the inverter.

A contractor needs protection from surge current, a good shunt trip breaker doesn’t.

The Sunny Island doesn’t need protection from inrush current on connection, it’s the contactor terminals that weld themselves shut with the arc upon connection.

 

[SilverbackMP]

You will need some way for the BMS to disconnect the batteries from the inverter.

A contractor needs protection from surge current, a good shunt trip breaker doesn’t.

The Sunny Island doesn’t need protection from inrush current on connection, it’s the contactor terminals that weld themselves shut with the arc upon connection.

I have the REC precharge modules for each battery. Is that enough? Or do I need something else? This system x8 plus the master module (and I think I have extras too, 2 is one and one is none): https://www.offgridsoftwaresolution...-pack-kit-builder/#select-your-system-voltage

Thanks for you help.

 

[toms]

It’s not clear in that package if you have current shunts and contactors for each pack.

I haven’t used the REC in master/slave configuration, but for a single REC to work with the Sunny Island you need a current shunt.

As i said, the pre charge module is just to protect the disconnect contactor from arc damage due to inrush current as you connect the Sunny Island.

 

[SilverbackMP]

It’s not clear in that package if you have current shunts and contactors for each pack.

I haven’t used the REC in master/slave configuration, but for a single REC to work with the Sunny Island you need a current shunt.

As i said, the pre charge module is just to protect the disconnect contactor from arc damage due to inrush current as you connect the Sunny Island.

Yep, have the current shunts and contactors.

I almost went with your suggested setup and then decided I wanted/needed more storage and wasn’t sure how doubling or tripling such a setup would affect the system…and wanted more monitoring on my first big system. But I will look hard at the way you do things if I need supplementary system. It’s nice and KISS.

 

[toms]

Yep, have the current shunts and contactors.

I almost went with your suggested setup and then decided I wanted/needed more storage and wasn’t sure how doubling or tripling such a setup would affect the system…and wanted more monitoring on my first big system. But I will look hard at the way you do things if I need supplementary system. It’s nice and KISS.

That sounds fine. It should be a fantastic setup when you have it commissioned - nice one!

 

[OffGridForGood]

I would expect the 96kW of ESS may be too small to make the best use of the 72 375W PV panels, at least when the daylight is longer again. No idea what the total loads (Whr) are going to be in this set up, but two houses plus a workshop seems like a lot more battery may be in order.
It will depend a lot on daily consumption, and how many poor PV days you expect to have. That or running the generator more often.
I can imagine days with say 21kW coming in from the PV and by early afternoon the batteries are all 100%, and there is no more storage available.
You have a good set up for ESS expansion, if it turns out you need more you have the space.

 

[SilverbackMP]

I would expect the 96kW of ESS may be too small to make the best use of the 72 375W PV panels, at least when the daylight is longer again. No idea what the total loads (Whr) are going to be in this set up, but two houses plus a workshop seems like a lot more battery may be in order.
It will depend a lot on daily consumption, and how many poor PV days you expect to have. That or running the generator more often.
I can imagine days with say 21kW coming in from the PV and by early afternoon the batteries are all 100%, and there is no more storage available.
You have a good set up for ESS expansion, if it turns out you need more you have the space.

It’s sized (right now) for winter. I will dump some of the summer excess into electric water heaters and daytime use only mini splits on various outbuildings (not really covered above) for semi climate controlled storage. AC coupled so this should work out well (I think).

I don’t have the second house built as of yet and that will be a couple of years away (barring societal collapse and/or world war between then and now).

Shop might not use much power on a given day or it may use a ton when I fire up a 3-5hp dust collector and wood working machines. Will have independent mini splits for AC only, fridge, couple of freezers, air exchanger. Radiant floor heat powered by wood with propane backup.

My mom’s house won’t draw much. Energy star rated fridge (we just replaced her 25 year old propane unit), smallish TV, couple of higher SEER mini splits (probably two 9,000 BTU units). Stove, dryer, secondary heat are propane. Primary heat is wood.

But yes, I’ve kind of made it modular so I can easily “plug in” more of everything except more total continuous power draw.

I thought about provisioning for a SMA multicluster box for more Sunny Boys, but that introduces more complexities into the system and more risk for a complete system failure should we get a lightning strike.

If I need more continuous power, I’d rather have more independent systems for redundancy..and with a series of transfer switches, I think I could share that power from one chunk to another should one portion have issues.

Plus the multicluster box is $14k. That buys a lot of other stuff.

 

[SilverbackMP]

We got almost half the panels hung today. Now that we know what we are doing, we can fly through the rest this week.

 

[OffGridForGood]

I like they way your using that natural slope to advantage, I wish my slope faced South instead of North!
Great to see your progress, I bet you're getting excited to see that PV connected and producing!