Confusion regarding SMA product

[SolarPrep]

I'm hoping one of the forum members who is familiar with SMA can clarify what the intent might be for the SMA storage unit with autotransformer. I read some posts from Hedges on this topic, but in the end am still confused.

I understand the role of the Sunny Island and Sunny Boy. When it comes to the storage devices, I'm not so sure. In particular how you might use the devices that have the autotransformer. From what I read, they only work with a select group of high voltage batteries. If there is no way to make them work with batteries you build yourself, and pair up with Orion, REC or some other BMS, then it wouldn't work for me.

Is there something I'm missing?

Thank you.

 

[mopat]

the new SMA
Automatic Backup Unit (ABU) is a truly integrated solution for whole home backup power. The ABU consists of several
components. The first is a 200 Amp rated contactor, which automatically disconnects the home energy system from grid power
during a power outage. The integrated autotransformer balances up to 5 kVA of imbalance across phases, reducing the potential
for system interruption during backup mode operation due to imbalanced loads within the home. The solution also includes
built-in energy consumption metering with pre-installed current transformers, eliminating the need for additional hardware and
labor. Two 50 Amp breakers are included for landing PV and energy storage inverter output, which also reduces hardware
needs. Finally, the ABU features an SMA backup controller, which manages and stabilizes the microgrid by monitoring solar
generation, load consumption, and battery state-of-charge.

 

[Dzl]

@Hedges has a good bit of knowledge/experience and a lot of enthusiasm for SMA, maybe he will chime in

 

[SolarPrep]

mopat: I don't think I did a good job of framing my question. I read that description you pasted in. I also understand WHAT an autotransformer does. What i don't get is if this unit has to be paired with a Sunny Island, or a Sunny Boy, or if it works with other stand alone units. I assume that is what the 50 amp breakers are for, but does it have to be an SMA product?

When I Google SMA, a bunch of permissions pop up that I don't want to agree to, and I find it hard to search their site for information. I cannot find any reviews of this equipment by anyone who has used it. Would like to know more.

Thanks!

 

[mopat]

does it have to be an SMA product?

no

 

[SolarPrep]

I found this today:

2.1 Intended Use
The Automatic Backup Unit is an optional accessory for the Sunny Boy Storage inverter. It contains
an automatic transfer switch, SMA Backup Unit Controller, overcurrent protection for the inverter(s)

and optionally an integrated energy meter and current transformers. In the event of grid failure, the

Automatic Backup Unit disconnects the PV system, loads and the Sunny Boy Storage from the utility

grid and creates a battery-backup grid. The battery-backup grid supplies loads that should continue

to be supplied with electricity in the event of grid failure. In the event of grid failure, the

Sunny Boy Storage supplies the loads with energy after a short switching time. The PV system

supplies additional energy that can be used to supply the loads and charge the battery.
The product is certified for use with the following SMA inverters:
• SBS3.8-US-10 / SBS5.0-US-10 / SBS6.0-US-10
Use of the product with battery inverters of manufacturers other than SMA is not permitted.

Cannot believe I didn't see this before. I'm not up on the SBS (Sunny Boy Storage) units, but believe they only work with select batteries.

More reading to be done....

 

[Hedges]

@Hedges has a good bit of knowledge/experience and a lot of enthusiasm for SMA, maybe he will chime in

The @ sign doesn't email me. Maybe it shows up under the bell icon, but I just click through my email.

Sunny Boy Storage is a 240V battery inverter without transfer relay, meant to store surplus power, for instance to avoid exporting PV to grid, and then avoiding import at high rate times. It looks to me like it is a reprogramed Sunny Boy PV inverter.
It works with a 400V battery and has very low maximum short circuit current allowed. Not really a 400V battery but something like a 48V battery with a boost converter. I haven't seen any circuits for DIY of the battery.

Automatic Backup Unit as noted by others is a 200A transfer switch and an auto transformer to form a neutral, so the 240V can provide 120/240V split-phase.

So far, SBS can't be stacked in parallel for higher wattage off-grid. It also has only 9kW surge rating.

It should work by itself or with Sunny Boy.
I've wondered if it could attach to the island grid of a Sunny Island. It does do UL-1741-SA so would curtail output when frequency rises. But I don't know if it would also ramp up charging, so make use of power from Sunny Boys that would otherwise be curtailed. Only documents I've seen are about grid interaction including time-based and linked by internet to some outside control.

 

[agarg]

The @ sign doesn't email me. Maybe it shows up under the bell icon, but I just click through my email.

Sunny Boy Storage is a 240V battery inverter without transfer relay, meant to store surplus power, for instance to avoid exporting PV to grid, and then avoiding import at high rate times. It looks to me like it is a reprogramed Sunny Boy PV inverter.
It works with a 400V battery and has very low maximum short circuit current allowed. Not really a 400V battery but something like a 48V battery with a boost converter. I haven't seen any circuits for DIY of the battery.

Automatic Backup Unit as noted by others is a 200A transfer switch and an auto transformer to form a neutral, so the 240V can provide 120/240V split-phase.

So far, SBS can't be stacked in parallel for higher wattage off-grid. It also has only 9kW surge rating.

It should work by itself or with Sunny Boy.
I've wondered if it could attach to the island grid of a Sunny Island. It does do UL-1741-SA so would curtail output when frequency rises. But I don't know if it would also ramp up charging, so make use of power from Sunny Boys that would otherwise be curtailed. Only documents I've seen are about grid interaction including time-based and linked by internet to some outside control.

It is possible to hook up micro inverters from the combiner box to the PV input of the ABU?

 

[Hedges]

https://files.sma.de/downloads/SBSABU-DUS185117.pdf

ABU has "circuit breakers for PV inverter", I think you could connect any string or micro inverters there.

Sunny Boy Storage would then interact with the PV inverters, when grid is disconnected. If those do frequency-watts (Rule 21), their output power can be modulated to match load + charging.

If they don't modulate power, they would switch on and drop off; maybe such operation is acceptable, or maybe it would cause wear (to relays, etc.) If SBS could be configured to run battery down for a while, then re-enable PV inverters and charge up for a while, reducing rate of cycling. I don't know, haven't worked with it. You want "Rule 21" inverters.

Some people have had problems AC coupling microinverters to battery inverter, and others got it working OK. No guarantee that will be well behaved, even if they are "Rule 21".

https://files.sma.de/downloads/SBSXX-US-DS-en-22.pdf

I'm not recommending SBS, but I bring it up because it is SMA an has some useful functions, regarding charge/discharge for peak shaving as well as backup. It is 6kW, 9kW surge, and can't be stacked for additional power. It is affordable, but compatible batteries are expensive.

What I have and recommend (if it meets your needs) is Sunny Island. 6kW, surge 11kW, stackable up to 4 units. It does not have peak shaving functions but can do zero export by cycling its batteries and using grid only when needed. It has generator support and other features for off-grid. Expensive, but you can get liquidation units new in the box for about half price.

https://files.sma.de/downloads/SI6048US-DS-en-28.pdf

I would imagine the new European model Sunny Island will arrive in the U.S. eventually, and probably have grid support and peak shaving.

There is a new SMA hybrid inverter. Maybe not for sale yet.
I think it has DC coupled PV, grid input, battery backup. But does not AC couple to grid tie PV inverters.

Discover the Sunny Boy Smart Energy | SMA America

The hybrid inverter at the heart of the SMA Energy System, with three backup options: Sunny Boy Smart Energy ► Discover now!

www.sma-america.com