SolarEdge Battery Cold Start

No idea, but I hope it is not #1. I have a similar system but have not yet experienced back-up operation.

I'm curious about this. In my phone app I can set the Backup Reserve for anything between 9% and 100%. You can see that in this screenshot, except this one says 7% minimum.

Backup_Settings%20900X650.jpg

I presume it needs some juice to keep the brains alive until either the PV steps in or the grid is back online.

I keep mine set for 50% and that is the minimum it reaches daily when the grid is up. I assume if the grid went down I'd have have access to battery use until it reached 9%.

If it's a 400V battery, 9% would be 36V (or 7% being 28V). That's a lot higher than your 6V. Not sure that's a problem, but maybe.

Solar Edge can see a lot of your info from their office, so you might give them a call. Or since it is new the installer ought to sort it out.

Considering the mounds of literature and videos Solar Edge produces one would think they would have prepared some deeper information about system backup behavior. Maybe I missed it?

I hope you'll let us know how this resolves.

At the time, the reserve was set to 20% and the battery had charged to 100% before the outage. It then proceeded to run on a combination of solar (until sunset) and battery until it reached ~5% when it shutdown. The installer said the 5% was a safety reserve that the battery will not go below. It is separate from the user-settable reserve. This is reasonable, I think, as rechargeable batteries do not take well to being completely discharged to 0. The 20% is the level that the battery will discharge to during normal operation (typically at night) to power the load with stored energy rather than draw from the grid. I see this nightly as I run on battery until about midnight (depends on what the post-sunset load is). In this scenario, the battery will discharge to the user-set reserve.

I don't think the battery voltage varies linearly with state-of-charge.

Based on my one data point, in a grid outage, the battery will discharge to 5%. During night normal operation, it will discharge to the reserve you have set. There could be different behavior if you have a more complex battery profile configured. Mine is set for maximum self-consumption; that's all the installer will configure.

I think that behavior is correct. The part I have a problem with is that when the sun rises and there is PV available but not grid power, the system should cold-start and start either charging the battery or start powering the load.

I have a neighbor with an identical SE system, except more batteries. He lived thru the night on battery and when the sun came up, he continued to power the load and charged the battery back up. He never went dark so didn't need to cold-start.

It shouldn't, but that's another detail SE does not proactively share. Where did you measure the voltage? Somewhere under the casing?

I agree with your description of the backup operation. And am concerned about the cold start reluctance. Glad your neighbor's system operated as we'd expect -- that gives me confidence. If I am here and the grid goes down I will make sure to maintain enough reserve to keep some LED lights on at a minimum -- and hope Annie is correct about the sun coming out tomorrow.

Did your installer not have any comment on the battery error message you saw, or any other ideas why the cold start was a non-starter?

I measured the battery voltage at the inverter with the battery leads disconnected from the inverter. That was easier than taking the cover off the battery and looking at the MC4 connectors.

Maybe if I had aggressively shed load to conserve battery we could have lasted thru the night, but I didn't mind it running down and shutting off. But I expected it to cold-start in the morning. If the situation recurs, I may take a different approach.

Once the grid turned back on. the battery initially showed some fault (I couldn't find anywhere to see a fault code) but that cleared after a while (minutes, I guess, but I wasn't watching it) and eventually it started charging and all was well.

Tnx

If you call SE they can see the fault code. When I call I use the "installer" option and go to the relevant department. I think there's one for battery troubleshooting. Usually there's a wait so I use the call-back option.

I only had one opportunity to see a grid outage so far, just recently, and I saw a similar draw down. My battery was at the 20% reserve in the evening. Power went out in the morning, mid-storm, and the battery continued to draw down to 11%, and then the generator kicked in.

I do have some questions about your setup. I too have Energy hub + BUI + generator, but the generator was connected to a temporary subpanel for critical loads, because the BUI was not integrated with the generator, when I bought the system in July 2021. This January, my installer FINALLY updated the "latest?" firmware, but we are unsure of whether the integration is working yet. The release note only talks about a configuration with a third party ATS, between the BUI and main panel, with the generator connected to the ATS, although there is some discussion about the generator charging the battery during grid fail (which would not be possible with an ATS as they show in the notes).

It sounds like you have the generator integrated in with the BUI?
Do you have the new firmware that was available July 2022?
What version are your running, BTW?
Any other pointers about your integration?

I've been frustrated as hell with my installer, who has been dragging his feet on integrating this, and who won't call SolarEdge to get info on the integration statue (I hear there is a "designer lime" that installers can call). I'm trying to get them to complete the integration, if it works, or to implement the interim config that is shown in the release notes with a 200A ATS (instead of temp sub panel with critical circuits).

No generator. When the BUI, Inverter, and battery were commissioned, firmware was updated, presumably to whatever was current in March 2023. I don't see an indication of the FW versions.

Did you ever get a response from SolarEdge on this? I had a very similar situation happen. Though in my case it was a little worse. I have two inverters and two batteries. We had an outage a couple weeks ago and everything transferred over to battery backup as expected . At the time of the outage I had 40% remaining in both batteries, so I shed loads to a level that should have gotten me through the night. However, around 4 AM, the system shut down. At first I thought I must have miscalculated my consumption and at the time wasn't too concerned as I also assumed that once the sun came up it would charge the batteries back to a level that it would allow a cold start. However that didn't happen. When I dug into things a little further, this is what I found. First, I didn't miscalculate consumption. For some reason, only one of my batteries was being used while other wasn't getting depleted at all (even though I know both batteries work because while the grid is up I self consume from both of them every day). Not sure why that happened. But what that mean was that instead of each battery sitting at 20-25% at 4 AM, I had one at 5% and another at 40%. When the one battery got down to 5%, the inverter attached to it shut down. Unfortunately this was my primary inverter. When that inverter shut down the whole system stopped producing. When the sun came up, it did start to charge the battery attached to the inverter that was still running (but not producing), so the battery that was at 40% did get charged back up to 100%. However, the dead battery, attached to the inverter that was shut down, did not charge at all and that inverter did not start back up. Because of this, I had a system that wasn't producing any power even though I had plenty of sun and a battery that was fully charged. Once the grid came back online everything came back on and started working as expected. I have my installer working with SolarEdge on this to get a response (I really hope they don't come back saying this is as designed), but so far I haven't gotten any useful response.

No response from SE. I've given up expecting one. I think I've puzzled out what happened in my case (& maybe yours but I only have one inverter and battery). In my case, grid went down about 12PM and load switched to battery. Still producing more than consuming so battery stayed @ 100% until sunset. I didn't try to shed any load, expecting that the battery would deplete overnight and would cold-start at sunrise if the grid outage lasted that long. I THINK what happened at sunrise was that the panels started producing but very little (maybe a few 100 watts). The inverter tried to use this to power the load, which drew way too much current. The inverter detected the output under-voltage condition and tripped off. It then stayed off until the grid was restored.

I did some additional tests where I depleted the battery to reserve level (9%, I think), then turned off the grid, then aggressively shed load (to essentially just the inverter internal use). Then turned the grid back on. The inverter stayed on (but no load). It charged the battery. This allowed the sun to rise and the panels to produce enough to power the house load (~900W if I leave off any resistive heating loads). It was then charging and powering the load until I turned the grid back on. So I think it's working as designed.

What I think SHOULD happen is that if the grid is off, the inverter should power the load until the battery reaches its safety reserve (5%, I think), then drop the load. When PV starts to come up, the inverter should leave the load off and direct all energy to the battery until the battery reaches its user-set reserve (9% in my case), then turn the load back on. We know that the PV (maybe + battery) can handle this since it did this when the grid failed. It needs to NOT attempt to power the load with first-light PV & no battery. Maybe this behavior could be an option, either for the user (probably too hard to explain) or via setapp.

Another possible solution would be a battery profile to charge from PV in the early AM until, say, mid-morning, if this would send ALL PV energy to the battery (grid on or off), then self-consumption. If grid is on, PV would charge battery in the AM and load would be powered by grid. If grid was off, PV would still charge battery only and load would stay dark until MSC start time when battery+PV would power the load. I haven't tried this, however.

Thanks for the reply. That gives me a little more hope. I did not shut off all of my loads after the inverter shut down, I guess I assumed it was working the way you said it ideally should be designed, in that it would not try to produce any power until the battery was sufficiently above it's safety reserve. Unfortunately I don't have an AC disconnect between the grid and my BUI so I don't have any way to test this until the next outage. Sounds like during your last test the inverter stayed on the entire time right? Did you run a test where you let the batteries deplete to the point where the inverter detected the under-voltage and actually shut down and then were you able to get it to cold start without the grid (by shutting down all loads) and giving it sufficient time to recharge? The reason I ask is that I know everything will work as long as the inverter doesn't shut down, I've seen that happen. I'm trying to figure out if it has the ability to cold start if it does shut down due to depleting the batteries too far.

In another post, you added: "Still, it would be nice to have a way to restart a tripped inverter without the grid."

I watched a video that explained how to reboot a SE inverter, said to clear certain unspecified issues that may be present.
1) Turn off the AC connection from the grid.
2) Turn off the inverter's DC connection from the PV array.
3) Wait a minute
4) Turn on the DC connection
5) Turn on the AC connection

The instructor states that having done these steps, the inverter reboots and operation is restored.
Perhaps, after the sun begins producing useful power, while the tripped inverter remains asleep, cycling the DC switch might be enough to initiate the wake-up process again. Couldn't hurt to try it.

I'm not sure that procedure is what I was looking for as the grid is OFF throughout. I wanted to reboot the inverter without grid. (so no step 5). I'm pretty sure I tried turning off the DC and turned it back on after a delay and it didn't restart. I think that in general restarting without grid would be inconsistent with "grid-tied" and needing to sync with the grid frequency and phase. I guess the BUI is what allows it to start when there's nothing to sync to. Then when the grid comes back on, it drops the load for a few seconds while it syncs up.

Were you able to get the battery to charge without the grid up? The sequence above has the grid coming up before the batteries started charging.

What I’m trying to confirm is:
1). Grid goes down (ideally test is done by disconnecting grid from BUI not just inverter)
2). Battery gets depleted
3). Inverter shuts down
4). Loads are turned off
5). inverter start back up (this is key….does it happen?)
6). Sun comes up and time is given to charge
battery back to a sufficient level to begin handling loads
7). Loads are turned on, home is operating off grid
8). Grid turned back on

And if it does work this way, was anything special required in step 5 to get the inverter to start up after loads are shut down or does it do that on its own?

The test I did was short as I didn't want to inconvenience the other residents, but your sequence is pretty much what I did. Grid goes down was by turning off the main CB which is in front of the BUI. Steps 5 & 6 are reversed. The inverter comes back online at first light and starts powering the (non-existent) load and charging the battery. As PV wattage increases, it soon reaches the point where it can power my ~800W always-on load, so I can turn the load back on and all is well. The grid can come back on anytime later. I think that if I was just running on PV (no grid) & battery, I'm limited to the 7.6kW of my inverter. The only time I see loads that big are when the oven runs, the A/C is in its highest stage, of my car is charging. All things that I can avoid in the event of a grid outage. If I were to exceed 7.6kW or whatever PV+battery could supply, I think the inverter would trip and stay off until the grid was restored. If I did not shed load in the early morning, it would trip at first light as PV=small and battery=depleted .