DIY battery system for SMA Sunny Boy

[Eljevi]

Hi,
I have a 11.5kW grid-tied solar system using a SMA Sunny Boy 6.0 and 3.8 US-41 inverter both with the secure power supply (SPS).
I have started looking into adding Lithium Iron Phosphate batteries to the system as both a backup power during outages and to be used at night or other times the panels are not receiving solar energy to help reduce the power bill.

I'm looking into building my own system as the cost to purchase and have battery systems installed is quite high. (As one example the company who installed the solar say they can install a 10kW Sonnen Core to a 6 breaker critical load panel for $13k).

I've tried getting information about the SMA inverters, but as others have mentioned in other posts in this forum it is quite difficult. When I spoke to SMA tech support they couldn't even answer my question about what battery voltage the inverters can accept. They passed me off to someone else but they are just trying to get me to buy the SMA storage inverter and ABU in addition to the battery without answering my questions. The system looks like it has some great features but definitely not cheap for the entire setup.

I was finally able to get some information from another local solar installer about the SMA inverter. It accepts 48V but in order to connect batteries to it I would need to get a conversion kit for $500 which is not a big deal. However, according to him if a battery system is connected directly to this inverter it has no way of monitoring the batteries and will not switch between the battery and grid automatically nor will it keep it charged appropriately.

So, with all that background information my question is, has anyone built their own battery system including the BPS, charge controller, and other electronics to monitor the power and then switch between solar, battery, grid safely?
What equipment do you recommend?
Do you have experience interfacing with the SMA sunny boy inverter?

I would appreciate any insight you have to get me going in the right direction as I have just started to dig into this and thankfully came across this forum.

Thanks

 

[Trkarl]

I believe you need a sunny island inverter which syncs with the sunny boy grid inverter and acts as a charge controller for the batteries and keeps the sunny boy working when the grid goes down. A buddy of mine has two sunny boys and two sunny islands hooked to his batteries for backup.

I just have a sunny island 5048 which I use for my house. I don’t grid tie and just use charge controllers for my batteries.

 

[Eljevi]

Thanks @Trkarl
I haven't looked into that option too much because I want to keep my costs down.
What I would like to do is basically build my own system from scratch. I've watch several YouTube videos of people building their own systems up but no one has done it specifically with the SMA Sunny Boy inverters. It seems like SMA doesn't like to play nice with others but I know someone has had to have done it before.

 

[Eljevi]

Has anyone heard of the conversion kit for the Sunny Boy to allow battery connections to it?
A solar installer mentioned it to me but I can't find anything about it.

 

[Maitake]

Sunny boy is a string inverter. No battery possible.
Sunny island is a battery inverter. No PV connection possible.
They can work together to create an ac coupled PV storage system.

 

[Shinebox]

You need a battery inverter to connect to the Sunny Boys. Best bet is to connect Sunny Island(s) for tight integration, but not absolutely necessary. You don’t need anything special to do this… no special converter or anything like that. For LFP batteries you WILL need a BMS capable of talking to the Sunny Islands over Can Bus, such as a REC SI. I speak of Sunny island in plural because generally people use two of them, each single phase 120vac to get 240vac split phase at 12000 watts. Some people use one and then install an autoformer to bump up the output of a single SI to 240v.

Long story short, Sunny islands are designed to work with 48v nominal. They will work well with LFP so long as you have a BMS that communicates with the SI. Sunny boys configured with SI’s makes for a very robust system. Sunny islands are very nice, but also expensive.

If you search for Sunny Island on this forum, there is lots of relevant information for you to digest.

 

[Eljevi]

Thanks @Maitake

 

[Eljevi]

You need a battery inverter to connect to the Sunny Boys. Best bet is to connect Sunny Island(s) for tight integration, but not absolutely necessary. You don’t need anything special to do this… no special converter or anything like that. For LFP batteries you WILL need a BMS capable of talking to the Sunny Islands over Can Bus, such as a REC SI. I speak of Sunny island in plural because generally people use two of them, each single phase 120vac to get 240vac split phase at 12000 watts. Some people use one and then install an autoformer to bump up the output of a single SI to 240v.

Long story short, Sunny islands are designed to work with 48v nominal. They will work well with LFP so long as you have a BMS that communicates with the SI. Sunny boys configured with SI’s makes for a very robust system. Sunny islands are very nice, but also expensive.

If you search for Sunny Island on this forum, there is lots of relevant information for you to digest.

Thanks @Shinebox
When you say the island is not necessary and no other special inverter is required, what other options are you referring to?

From what I am seeing so far with the island it looks like a great system, but like you said it is expensive. I also have two inverters (3.8 and 6.0) so I believe I would need two regardless to take advantage of the full system.

 

[Pyrofx]

Gotta have islands. The supply the 120 from batts.

 

[Shinebox]

Thanks @Shinebox
When you say the island is not necessary and no other special inverter is required, what other options are you referring to?

From what I am seeing so far with the island it looks like a great system, but like you said it is expensive. I also have two inverters (3.8 and 6.0) so I believe I would need two regardless to take advantage of the full system.

If you went with the SI route, you could use one SI if you wanted, you would get single phase 120v, unless you added an autoformer, which isn’t terribly cheap, so while more expensive to get two SIs, it’s worth it imo.

As far as other options, you can add any battery inverter capable of AC coupling to your Sunny boys. Schneider, Sol Ark are a couple that come to mind. The bigger picture is that your Sunny Boys are only capable of inverting Solar DC into AC for domestic use and grid tie. If you want batteries, you NEED a battery inverter. Because you already have an installed system, an AC coupled inverter is easier to implement. Because you have Sunny boys, the SI is a good fit, and it happens to be an extremely robust and dependable piece of kit. You will find that many of your other options, like the Sol Ark and Schneider are hybrid units and have their own Mppt controllers. This would allow you to connect panels direct to these inverters.

 

[George_Moore]

Sunny boy is a string inverter. No battery possible.
Sunny island is a battery inverter. No PV connection possible.
They can work together to create an ac coupled PV storage system.

A string inverter can work with batteries. You need a charge controller in front of it, and it won't even know it.

 

[George_Moore]

Has anyone heard of the conversion kit for the Sunny Boy to allow battery connections to it?
A solar installer mentioned it to me but I can't find anything about it.

I have heard of putting a generic charge controller in front of the sunny boy to work with batteries..

 

[Eljevi]

I have heard of putting a generic charge controller in front of the sunny boy to work with batteries..

I'm interested to hear more details on this.

 

[Hedges]

I use Sunny Island with AGM batteries and older model Sunny Boys.

Sunny Island is your best bet (you can buy for about $3000 on eBay), or other battery inverters that support AC coupling to GT PV could be used.
One SI and one used transformer, two 120V secondaries as auto-transformer, is a possibility. Then all 6kW of one SB will go through a single pole breaker to the grid, probably exceed 120% rule.
Better to get 2x SI.

Sunny Boy isn't designed for battery short-circuit current. Inrush could be an issue, so precharge if you try this.
You're planning to use it for Secure Power, so 2000W max.

"Rated MPP Voltage range 220 – 480 V"

Is this just for occasional backup? How about 10x 12V lead-acid batteries in series?
Let one SB secure power feed some sort of battery charger (maybe 10x 12V chargers) and the other SB has battery and more PV panels?
It'll be a big experiment, tell us what happens.

 

[Eljevi]

I use Sunny Island with AGM batteries and older model Sunny Boys.

Sunny Island is your best bet (you can buy for about $3000 on eBay), or other battery inverters that support AC coupling to GT PV could be used.
One SI and one used transformer, two 120V secondaries as auto-transformer, is a possibility. Then all 6kW of one SB will go through a single pole breaker to the grid, probably exceed 120% rule.
Better to get 2x SI.

Sunny Boy isn't designed for battery short-circuit current. Inrush could be an issue, so precharge if you try this.
You're planning to use it for Secure Power, so 2000W max.

"Rated MPP Voltage range 220 – 480 V"

Is this just for occasional backup? How about 10x 12V lead-acid batteries in series?
Let one SB secure power feed some sort of battery charger (maybe 10x 12V chargers) and the other SB has battery and more PV panels?
It'll be a big experiment, tell us what happens.

Thanks Hedges. It seems like everyone is pointing to the Sunny Island but I have a lot more research to do. This battery system will be used for backup when the grid is down but also to be used at night or cloudy days.
For the batteries themselves I might just keep it simple and get the 48V KONG ELITE - LiFePO4 - 300Ah - 15.0kWh

 

[Hedges]

If you use a LiFePO4 battery with Sunny Island, ideally you would get one with a BMS it talks to. That lets it hold voltage for balancing, etc.
There are a number of compatible commercial batteries, and one model of REC BMS works.

https://files.sma.de/downloads/SI-LiIon-TI-en-46.pdf

Otherwise, Sunny Island doesn't have lithium parameters. You have to set VRLA parameters so they will meet lithium requirements, including zero temperature coefficient for charge voltage.


Sunny Island, at least the present US model, doesn't have features for peak load shaving and shifting time of use. Sunny Boy Storage does. Perhaps when the newer European model Sunny Island appears here, those will be implemented.

Sunny Island is UL-1741 listed but not UL-1741-SA. That should mean it isn't approved as source of net metering backfeed to the grid (which it would do with DC coupling), but I think it should be allowed to connect, as a UL listed device, with your Sunny Boys as the approved backfeeding inverters.

 

[Eran]

Thank you! I'll search for that.
My Trip switch shuts off when the Grid comes back out of and outage. Do I change the Setting of parameter "Max. battery charging current" or "Max. AC charging current" its 32 mA trip i Have

Thank you in advance.

 

[Hedges]

Which device are you referring to that has a "Max ___ charging current" parameter?

Sunny Island has both those parameters. When configuring with quick-start guide, it set the following parameter quite high.
"BatChrgCurMax Charging current of the battery (10 A to 1,200 A)"
Because I have a smaller battery than the 100 Ah per 1kW of PV recommended, it would have charged faster than the 0.2C rate I wanted, so I adjusted that parameter.

I don't follow what "32 mA trip" refers to.

 

[Eran]

Thank you very much!
Sorry Hedges - I am referring to an Sunny island 8.0H.
The 32 mA is a trip switch, its used to protect the Inverter from over loads.

Would you happen to know about adding the system to https://ennexos.sunnyportal.com/, it does not search for my system and gives the following message

• Ensure that the PIC and RID are correct.
• Ensure that the device has an Internet connection.
• Ensure that the device is not already registered in a Sunny Portal system.
• If the device is already registered in a Sunny Portal system:
  • Reset the device to default settings (see operating manual).

Thank you in advance.

 

[Hedges]

I've never touched the 8.0H, in the U.S. have 6048US model.

32 mA sounds more like ground-fault limits.
I see in manual 8.0H can deliver 26A from inverter, and 50A pass-through (from grid? Generator? "for off-grid systems).

I don't use the portal or have my system internet connected. I use local hardware to access settings, presently have the (obsolete) Sunny Web Box. That has known vulnerabilities, and I only use it direct connected to PC.

Of course your system would have to be visible on your local network before it could be seen by Sunny Portal. And then whatever is needed to get past any firewalls you may have.