Sunny Islands vs Sol-Ark 15K for existing SMA-based Grid-Tied System

[kdub23]

Hi All,

I have an existing 18.3kw PV system fed through 3x SMA Sunny Boy 6.0-US-41's. It's hard to overstate how extremely happy I am with those inverters in terms of performance and reliability. I installed and designed the entire system and really wish I would've started reading the forum sooner.



I am planning on adding +/- 30kwh of SOK LiFePo batteries and have hit a little analysis paralysis in regards to a hybrid inverter for a home-backup solution. Not having a dedicated critical loads panel, my goal is to have something as easily "retrofittable" as possible. I've narrowed down my choices to the Sol-Ark 15K or 2x Sunny Islands.

Here are my high-level pros and cons for each as I see it:

• Sol-Ark 15K
  • Pro: All-in-One and will free up some space on my garage walls
  • Pro: 200-Amp passthrough. Enough said.
  • Pro: could sell my existing 3x Sunny Boys to recoup some costs
  • Con: Unknown reliability and some people had issues with unbalanced loads with the 12K.
  • Con: Lackluster data collection and display/app (from what I've seen).
• 2x Sunny Island 6048
  • Pro: Can drop in alongside my existing PV Inverters
  • Pro: Made by the Germans. They seem to know what they're doing.
  • Pro: Multiple devices and not one single point of failure
  • Con: 56Amp input would mean I would have to send one PV inverter directly to the grid and only have two on the load side of the SI's. (I need clarification on this)
  • Con: Multiple devices mean less room for shovels and rakes and weedeaters on my garage wall.

I'm looking for help in deciding between these. I've attached a one-line diagram of my current system. Am I missing anything important to consider?

Thanks for the advice!

 

[Wet1]

The versatility, zero export, and simplistic AIO package with the 200A passthrough eliminating the need for wiring a backup panel is what has pretty much sold me on the SA 15K. Not to mention their CS and TS is second to none. Yes, it is a new system, but I suspect any bugs that might be found will be handled quickly. The possible unbalanced load issue seems like a non-factor for me since most heavy loads are 240V anyway.

 

[bteigrob]

you don't want a dedicated critical loads panel. So you want the entire house backed up?

 

[kdub23]

you don't want a dedicated critical loads panel. So you want the entire house backed up?

I don’t want to rewrire my house for a CL panel. I can easily shut things off and conserve manually. I basically want enough to comfortably get through the night.

 

[bteigrob]

OK, have you checked out the Sunny Boy Storage? I am very much in the same position you are in. I have panels with a grid tie Sunny Boy 7.7. The power company here doesn't recognize back feeding (they actually charge me for the power that I would back feed). So now I am looking at some storage to get through the night and use as a back up incase grid goes down.

The Sunny Boy Storage appears to be a cheaper option up front compared to the Sunny Island, but SBS requires high voltage batteries versus low voltage for the SI.

I am not familiar with the Sol-Ark. I should probably read up on it myself and maybe I would also consider selling SMA and migrating over to that just like you are considering.

 

[copec]

There are enough smart panels in the pipeline that you can setup automatic load management in the future and not doing a dedicated critical loads panel. I have my whole house going through a single Deye 8k now and the grid going down hasn’t really been a problem for me managing load (I am adding another one though).

If you think you might eventually go all off-grid, the sunny islands can pretty much start any load thrown at them, and handle overload incredibly well, also you would have more power to run loads when the sun is out.

The Sol-Ark should be slightly more efficient in off-grid mode, and it seems like a single 15k would make the setup elegantly simple conceptually speaking, but they are much more sensitive to L1/L2 balance and overload issues (although my experience from my Deye indicates they are the same as any other high frequency inverter).

We should pull @Hedges into here as he has an SMA setup.

 

[kdub23]

OK, have you checked out the Sunny Boy Storage? I am very much in the same position you are in. I have panels with a grid tie Sunny Boy 7.7. The power company here doesn't recognize back feeding (they actually charge me for the power that I would back feed). So now I am looking at some storage to get through the night and use as a back up incase grid goes down.

The Sunny Boy Storage appears to be a cheaper option up front compared to the Sunny Island, but SBS requires high voltage batteries versus low voltage for the SI.

I am not familiar with the Sol-Ark. I should probably read up on it myself and maybe I would also consider selling SMA and migrating over to that just like you are considering.

Needing to use high-voltage batteries and their Automatic Backup Unit is a big turnoff. I hear great things about the Sol-Ark, just a little trepidation on moving over to that.

 

[RayofSunshine]

The Sol-Ark's battery agnostic "feature" (any chemistry, manufacturer, as long as it's 48V) is a selling point for me. They are announcing close "integration" with more battery ESS manufacturers all the time. For me, LiFePO4 is the way to go, so the integration is important.

As far as the load imbalance goes, from my research, you have that possibility with any HF transformerless inverter. I think it's been established that if you expect unbalanced loads on L1 & L2 (due to high wattage 120V devices (curling iron, hair dryer, portable electric heather, etc.) being turned on simultaneously), you can add an autotransformer to mitigate the issue (at the cost of extra power consumption for the transformer). As mentioned, another solution (possibly best long term) is a smart electrical panel. Sol-Ark announced their Smartloads 14 some time ago. It integrates with your main panel so no critical loads panel is needed. It should be released sometime soon. From the specs, it seems to be very competitive with the other smart panels out there. I directly asked Sol-Ark support if it will help this line imbalance issue. The response was "TBD - I imagine we will shed loads to keep the system from overloading on one phase but I am not 100% certain so I do not want to misguide you."

 

[kdub23]

The Sol-Ark's battery agnostic "feature" (any chemistry, manufacturer, as long as it's 48V) is a selling point for me. They are announcing close "integration" with more battery ESS manufacturers all the time. For me, LiFePO4 is the way to go, so the integration is important.

As far as the load imbalance goes, from my research, you have that possibility with any HF transformerless inverter. I think it's been established that if you expect unbalanced loads on L1 & L2 (due to high wattage 120V devices (curling iron, hair dryer, portable electric heather, etc.) being turned on simultaneously), you can add a transformer to mitigate the issue (at the cost of extra power consumption for the transformer). As mentioned, another solution (possibly best long term) is a smart electrical panel. Sol-Ark announced their Smartloads 14 some time ago. It integrates with your main panel so no critical loads panel is needed. It should be released sometime soon. From the specs, it seems to be very competitive with the other smart panels out there. I directly asked Sol-Ark support if it will help this line imbalance issue. The response was "TBD - I imagine we will shed loads to keep the system from overloading on one phase but I am not 100% certain so I do not want to misguide you."

I’ve got my SOK’s and 15K in today. Let’s hope I made the right choice.

 

[Wet1]

Congrats! Looking forward to hearing your feedback after installation.

 

[Hedges]

I've been called an "SMA whore", so you know what my recommendation is.

If you do use 2x SI 6048US, 13.4 kW is limit through relays.
Put 2x SB 6.0 on output of SI along with any critical loads, input fed from 70A breaker on main panel.
Use a load-shed relay from SI (or from critical loads panel) to an important loads panel. This would be disconnected if battery reaches 70% DoD (that value for lead-acid, other for lithium.)

Put 1x SB 6.0 on main panel.
Wire from the load-shed relay to an interlocked backfed "generator" breaker on main panel.

When power goes out, 2x SI & 2x SB keep critical loads operating 24/7, important loads as long as battery above 70% DoD.
You can manually turn off 70A breaker feeding SI, manually turn on "generator" breaker, manually turn off any unreasonable loads you don't want to try to power from backup system (e.g. electric furnace.)

With SB set to UL-1741-SA frequency-watts, it should be compatible with both direct grid usage and usage on Sunny Island. So switching one between those configurations is fine. (Any switching of input to an inverter should pause for 5 seconds with all power off before connecting to another source, ensuring inverter has disconnected and doesn't get hit with out of phase source.)

Additional Advantages of Sunny Island:

High starting surge ability.

Able to manage GT PV up to 200% of battery inverter rating.

GT PV can be on output (rather than a special input with generator shedding.)

Multiple boxes, 2x battery and 3x PV inverter in your case, provides redundancy. System can operate with some down for the count. An auto-transformer would be required to get by with single Sunny Island. Install temperature sensors in both so no rewiring required to make it work.

Good management of lead-acid batteries.

Additional advantages of Sol Ark:

Time of use shifting (I think). Sunny Island U.S. model doesn't offer that.

 

[Elexide]

Hi All,

I have an existing 18.3kw PV system fed through 3x SMA Sunny Boy 6.0-US-41's. It's hard to overstate how extremely happy I am with those inverters in terms of performance and reliability. I installed and designed the entire system and really wish I would've started reading the forum sooner.

View attachment 99543View attachment 99545

I am planning on adding +/- 30kwh of SOK LiFePo batteries and have hit a little analysis paralysis in regards to a hybrid inverter for a home-backup solution. Not having a dedicated critical loads panel, my goal is to have something as easily "retrofittable" as possible. I've narrowed down my choices to the Sol-Ark 15K or 2x Sunny Islands.

Here are my high-level pros and cons for each as I see it:

• Sol-Ark 15K
  • Pro: All-in-One and will free up some space on my garage walls
  • Pro: 200-Amp passthrough. Enough said.
  • Pro: could sell my existing 3x Sunny Boys to recoup some costs
  • Con: Unknown reliability and some people had issues with unbalanced loads with the 12K.
  • Con: Lackluster data collection and display/app (from what I've seen).
• 2x Sunny Island 6048
  • Pro: Can drop in alongside my existing PV Inverters
  • Pro: Made by the Germans. They seem to know what they're doing.
  • Pro: Multiple devices and not one single point of failure
  • Con: 56Amp input would mean I would have to send one PV inverter directly to the grid and only have two on the load side of the SI's. (I need clarification on this)
  • Con: Multiple devices mean less room for shovels and rakes and weedeaters on my garage wall.

I'm looking for help in deciding between these. I've attached a one-line diagram of my current system. Am I missing anything important to consider?

Thanks for the advice!

Cons on the sunny island are how picky they are with the approved battery list for lithium . You likely want to run in closed loop. They are no longer servicable, full replacement only. Their monitoring ain't that great either just us home assistant for the solark. Pros are you can have constant grid voltage present on the SI ac input as a backup power source and still chose to self consume your batteries and only use grid unless you reach low soc. The 15k will automatically always pass on that available power to your loads via the AC pass through relay. You can fix this with contactors that only turn on when it asks for charge from the gen. Which leads me to another 15k problem which is if you want to have a generator connected that's smaller than the inverter Max combined battery charge rate and the house loads together then you will want to turn on the grid Peak shaving mode and install the CTS, however when you do this it's going to now turn on the time of use automatically in the settings which means you need to set l the TOU slots to 100% and check all the charge boxes in every time slot. In my experience this means you're automatic generator start setpoint on the inverter no longer works so you will need a third party voltage monitoring relay to do the 2 wire gen start which is not as accurate as SOC based but in my humble opinion ends up being simpler and more reliable in the long run anyway.
Other Pros on the sunny island are how customizable it is and it's also got the input to tell it whether it's got Grid or generator connected to the AC to Via a transfer switch. All that said the worst part about the sunny islands is their weak ass relays. Sunny islands are also the best AC coupling inverters out there. You don't want to use the 15K with only AC coupled charge sources from PV because then you can't do a finished rate on your batteries since it is an on/off switch only. It cannot frequency shift to curtail solar.

Sorry for the rambling run on paragraph It's almost 3:00 a.m. and I can't sleep?

 

[Hedges]

All that said the worst part about the sunny islands is their weak ass relays.

Know anything about external transfer switches being used to bypass Sunny Island relays?
I thought I saw a 200A transfer switch to be used with the European 8.0H series.
The signaling relays can be configured to close when "on grid" (I'm not sure if that is distinguished from generator connected), but anything related to grid connection must be very reliable.

What conditions cause failure of the SI relays? With inverter supporting loads during "make" to grid, they could carry little to no current. Although, if only frequency not voltage is matched, I'd expect high line voltage to suddenly pick up all the load. Disconnect would be under load for some scenarios. Could be done with zero relay current under others.

Before getting multiple SI, I did consider tapping into the relay control signals to drive an external relay for L1/L2.

 

[Elexide]

I like your idea of tapping into those relay signals to operate external relays but I don't think I would want to do that for an inverter that's still under warranty?

I believe though i might be wrong that the sunny Islands have trouble switching in unision at the 0 point of the sine wave when you have multiple inverters in a stacked system. This causes them to be switching under current, which causes arcing, which causes them to burn, and then stick the next time.
It also causes one inverters relay to bear all the load of a leg while the other inverters relay is already open since they didn't switch in unison. .

Not only that they just simply don't seem to have a very high pass thru current. I believe that they are actually susceptible to sticking and seizing at current lower than what they claim to be rated for in other words their continuous current rating from the manufacturer is too high.

Not only that., you mentioned how there needs to always be that 5 minute time delay when switching ac sources.
That means it's extremely susceptible to issues with installers that aren't aware of this when they first set them up. Now they caused a scenario which might have slightly damaged the relays but won't show up until later down the road.
To me that is an Achilles heel.

 

[Hedges]

Rather than switching at zero point (of current, not voltage), what I mean is an inverter can supply a sine wave providing exactly 100% of the load and through relay is zero continuously, as sine wave goes up and down (to within shape of waveform which could be distorted.) So when relay opens, no current is flowing through it. Same when closing, if voltage across relay is zero, except to the extent the sine waves are distorted, near zero current flows the moment it closes. Normally SI produces 120V. It could boost to match grid, but don't know that it does.

I think the biggest threat to relays is closing into current, because the will bounce, arc, melt, and close again. Possibly welding.

5 minutes is a UL-1741 spec for qualifying grid voltage.
5 seconds is to ensure an inverter which was backfeeding the grid detects islanding and shuts off. You don't want to snap a transfer switch from one source (e.g. generator) to another source (e.g. grid) and have a Sunny Boy with its transistor H-bridge 180 degrees out of phase.
This is not something installers would normally encounter. But if putting in a transfer switch, its switching speed would matter. I'm using manual interlocked breakers.

The relay is 3 pole 30A. (I forget if that is 3PST or 3PDT). I'm not sure if that is 2x 30A poles in parallel to carry 56A, or 3x 30A poles. It crossed my mind the 3rd pole could be used to determine relay status, notice if it was welded.

I've set up a 3-phase system as well, 3x SI 5048US. A Sunny TriPower on the Island side feeds it, and only 6700W (56A) can backfeed the grid. I'm contemplating using an auto-transformer to make 120/240V split-phase out of that one leg of the 3-phase. Use a signaling relay that says "on grid" for additional qualification, but also a current transformer on the one L1 120V grid wire feeding Master SI: Connect other L2 phase if current > 30A, disconnect if < 10A. This could double the import/export power it supports. Beyond that, considering using CT and a uP feeding SpeedWire to do limited export.

 

[copec]

I’ve got my SOK’s and 15K in today. Let’s hope I made the right choice.

Did you get it installed? I've heard that they beefed up the 15k for good load starting, that a single 15k could start stuff that parallel 12k's couldn't.

 

[kdub23]

Did you get it installed? I've heard that they beefed up the 15k for good load starting, that a single 15k could start stuff that parallel 12k's couldn't.

I sure did. See here. While running the rest of my house, the 15K started my 4-ton upstairs A/C. I've since installed a soft-start, but before install, I measured an inrush of 117.5A. It did struggle a little, but impressive nonetheless.