This is going to be a bit of a rant born of frustration at (1) poor documentation and (2) wrong information being posted by people who should know better (I’m looking at you Sunsynk).

So, how does Smart Load REALLY work? First, a huge caveat. I don’t “know” from personal experimentation. This is my hypothesis based on reading forum posts and watching youtube videos and on what makes SENSE and what DOESN’T make sense. I do intend to verify my theory when I get some battery storage in a few weeks.

And finally, please please please set me straight if I’m wrong on any point. This is intended to be a conversation. Hopefully by the end of it we’ll come to some definitive answers.

There’s a pdf document about this somewhere.  I’ll try to find it and try to reconcile with it.

 

(I posted this in diysolarforum also)

How Smart Load Works (My Theory)

Deye/Sunsynk/Sol-Ark Smart Load

My hypothesis is that all of these inverters work the same. It makes no sense for them to work differently. Deye is the OEM for all of them. They each have a different UI, but I’m betting the underlying functionality is the same. Between 3 different user manuals, this is how I think they all work:

1. The GEN port can function as a smart load port
2. It’s for what I call semi-essential loads, striking a middle ground between non-essential loads (Grid) and essential loads (Load). It’s grid-tied, but depending on settings can remain “on” and using battery power even if the grid goes down, until a specified battery SOC is reached.
3. It is either “on” or “off” based on user-specified criteria. That’s it. On or off.
4. If “On Grid always on” is enabled, the port is live when the grid is available, without regard to any other settings. It’s just “on”, period. In this sense it’s similar to the Grid port.
   • What I don’t know is how much battery power, if any, is used in this mode. Since battery SOC is ignored, this leads me to believe that battery power may not even be used. It would be awesome if this is the case.
5. The “Power” setting is a trigger, not a limiter. (I call bullshit on the Sunsynk video and on their user manual)
6. The “Power” setting refers to total PV production, not “excess” production. This limits its value but it simply can’t measure excess PV because in many scenarios (zero export or off grid) there simply won’t BE any as PV output will be curtailed to match the load. Excess PV will be zero, even if there’s unused capacity. The inverter doesn’t actually “know” how much extra PV power there is because it never gets generated in the first place. I’ll set this to something less than my base load, so around 150w so that it’s on whenever there’s any solar power being generated and off otherwise.
7. Priority #1 for the inverter must be to power your loads. “Power” being a limiter violates priority #1.
8. Priority #2 must be to use all available PV before using battery or grid. Isn’t this the PURPOSE of the smart load port, to make productive use of excess solar power?
9. Limiting the smart load to only battery power (that Sunsynk video again) violates priority #2 and makes no sense. What if you have only a small battery limited to .5c? What if battery power is limited in Time of Use? What happens to your load if it can’t get the power it needs? This violates priority #1.

My desire is to use the smart load port to power an EVSE to charge an EV. I want to use whatever excess solar is available, supplemented by grid power. I don’t want to use battery. I hope to minimize the use of battery via the Power setting in Time of Use. For example, if I enable “On grid always on” to turn the port to always on, to charge overnight, I’ll set Power in Time of Use to a number just above my typical nighttime base load, like 1000w to avoid using a small battery to charge a big battery.

Ok, set me straight y’all.

From the manuals

The Sunsynk manual describes the Power setting as a limiter but this makes no sense at all. What if your load needs more power than this? This sounds like a great way to damage expensive electrical equipment. Why on earth would you do this? Why would you WANT it to work this way?

Both the Deye and Sol-Ark manuals describe this as a trigger.

The Sol-Ark manual specifically states that the smart load port is limited to 40A. Sunsynk (in a YT video) says it’s limited to 50% of the capacity of the inverter. Deye doesn’t say anything but a forum post says it’s only limited to the passthrough current. In my case any of these is more than adequate. I’m more limited by my electrical service (30A continuous) than I am by my inverter.