[RE-wrenches] Hybrid inverter with no battery

Fri Aug 1 08:20:31 PDT 2025

Ill try to find a block diagram to show the design and trade-offs of solar
AIO inverters , particularly when it comes to integrating grid, generator,
and PV charging into an All-In-One (AIO) system. The high-voltage DC bus
that all current Asian made units use simplifies the design and reduces
costs, but it does come with limitations when it comes to supporting
multiple power sources simultaneously and managing charging / MPPT
effectively.

 SolArk changed the game by marketing inverters with a higher daytime
rating (like the 15K inverter for daytime, despite being a 12K inverter at
night). That’s a clever marketing move to align with the fact that
inverters can directly convert the high voltage DC to AC adding extra
Output power.

It's my view that an isolated MPPT and inverter design for off-grid or
net-zero systems would, in theory, allow for more flexibility in managing
the power sources, *but the tradeoff is cost.* It’s a delicate balance
between performance and price. Many customers prioritize initial costs over
long-term efficiency or flexibility, which is why high-voltage DC bus
systems are more popular—because they are cheaper to build and scale,
despite their limitations. That combined with the fact that no one is
currently building an AIO that uses isolated power sections.

On Fri, Aug 1, 2025 at 10:58 AM Jay via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Does anyone have or know where to find an explanation of how the all in
> ones work?
>
> Like how does the CC work, battery charger etc. flow chart of the
> electrons.
>
> It’s still pretty mysterious to me and I’d like to know more
>
> Jay
>
> On Aug 1, 2025, at 8:46 AM, Harry Mahon via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
> 
>
> Sam – the SMA Backup Select is available for order from Authorized
> Distributors, but has not begun shipping (will likely be closer to Q4).
> Should be well under $1000.
>
>
>
> Sunny Boy Smart Energy had the Backup Secure (old SPS) function to provide
> 120Vac power to dedicated outlet(s), requires manual operation with
> dedicated switch.
>
> Can use Backup Secure with or without battery connected to inverter, up to
> 1,920W. Can also use with rapid shutdown on array, requires SMA Backup
> Start card accessory 9installs inside inverter) in that case.
>
>
>
> The new SMA Backup Select is an accessory that is an MID with included
> backed up loads panel.  Still only 120Vac power in an outage, but automatic
> switching and powers up to 7 circuits in house (no need to move plugs).
> Also can operate with or without battery, with or without rapid shutdown,
> up to 3,840W for 3.8-7.7kW SBSE inverter, up to 5,760W for the 9.6/11.5kW
> SBSE models.
>
> Datasheet: https://files.sma.de/downloads/BU-SLCT-US-50-DS-en_us-11.pdf
>
> Installation Manual:
> https://files.sma.de/downloads/SMABackupSelect-IA-en-10.pdf
>
>
>
> SMA Backup Home (full power of inverter in outage, 240Vac backed up loads)
> is likely not going to be available this year unfortunately.
>
>
>
> Best regards –
>
> Mike
>
>
>
>
> *Michael Mahon* (he/him)
> Solar Academy Manager  |  SMA America
>
> +1 916 918 9412
> SMA America <https://www.sma-america.com/> | Solar Academy
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>
>
> <https://www.sma-america.com/products/hybrid-inverters/sunny-boy-smart-energy>
> <image001.jpg>
> <https://www.sma-america.com/products/hybrid-inverters/sunny-boy-smart-energy>
>
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>
> *From:* RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> *On
> Behalf Of *Sam Haraldson via RE-wrenches
> *Sent:* Friday, August 1, 2025 7:09 AM
> *To:* RE-wrenches <re-wrenches at lists.re-wrenches.org>
> *Cc:* Sam Haraldson <sam at onsiteenergyinc.com>
> *Subject:* Re: [RE-wrenches] Hybrid inverter with no battery
>
>
>
> I have installed two of the SMA Sunny Boy Smart Energy hybrid inverters
> but only in a conventional solar-only, grid-tied design without batteries.
>
>
>
>
> https://www.sma-america.com/products/hybrid-inverters/sunny-boy-smart-energy
>
>
>
> There is a separate SMA Backup Select box required for off-grid backup
> operation and I have not laid eyes on it in person.
>
>
>
> - Sam
>
>
>
> [image: OnSite Energy] <https://onsiteenergyinc.com/>
>
> *Sam Haraldson*
>
> Operations Specialist
>
> (406) 551-6135
>
> 1515 N. Rouse Ave Bozeman, MT 59715
>
> Locally owned and operated since 2012
>
> [image: B Corporation] <https://onsiteenergyinc.com/bcorp>
>
>
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