Troubleshooting SMA and REC - Mostly (all?) Solved

[1201]

I’m really pumped for you that you got it ironed out. I had waffled on sunny islands in the past. Even picked @Hedges brain for weeks and got cold feet
Been following this thread with extreme interest.
Went from thinking I dodged a bullet to “ehh these are still worthwhile” all in a couple days ?
As you know, they contain all sorts of usefulness but the quirks were what scared me

For off grid use I don't personally believe there is a better inverter out there. Victron might be on the same level, maybe, but I don't think there is a higher level than the sunny island

 

[SilverbackMP]

My one remaining concern is I believe that the SIs can combine both generator power and battery power for more than a 100 Amps (240v) of output (with four SIs)...I just need to figure out how to get there with these settings. It's only for the very heaviest of (small) shop activities do I have a concern.

 

[1201]

My one remaining concern is I believe that the SIs can combine both generator power and battery power for more than a 100 Amps (240v) of output (with four SIs)...I just need to figure out how to get there with these settings. It's only for the very heaviest of (small) shop activities do I have a concern.

Isn't that the normal operation?

 

[SilverbackMP]

Isn't that the normal operation?

I think so, but it seems that "max" in terms of battery charging means draw every bit of the power allotted to it by either the BMS setting (Max charging current per inverter device) or SI setting (battery charging current max) or both...and need to think through how all of that plays with the 112 A (on each leg) capacity. And how that amperage converts between 48v batteries and 120v legs and 240v main.

So if I tell the batteries that they are able to use 75-80% of the generator for charging (to both hit the sweet spot for the generator and to stay under 80% continuous limit of the 125A breaker)...and a demand for power comes on line in the process, will it switch to passing through that generator AC and switch to discharging the batteries to make up the rest? I am not convinced that this is the case...the way that it is currently operating. I could very very much be wrong...all of this shit does my head in. There's a reason that I am not an engineer (besides the fact that the engineering university in my state had/has a lack of girls).

 

[1201]

I think so, but it seems that "max" in terms of battery charging means draw every bit of the power allotted to it by either the BMS setting (Max charging current per inverter device) or SI setting (battery charging current max) or both...and need to think through how all of that plays with the 112 A (on each leg) capacity. And how that amperage converts between 48v batteries and 120v legs and 240v main.

So if I tell the batteries that they are able to use 75-80% of the generator for charging (to both hit the sweet spot for the generator and to stay under 80% continuous limit of the 125A breaker)...and a demand for power comes on line in the process, will it switch to passing through that generator AC and switch to discharging the batteries to make up the rest? I am not convinced that this is the case...the way that it is currently operating. I could very very much be wrong...all of this shit does my head in. There's a reason that I am not an engineer (besides the fact that the engineering university in my state had/has a lack of girls).

I've tested it with the grid and the battery supplements the grid. So if I set maximum current to 10 amps and a 20 amp load comes on the sunny island will invert from battery to support the load.
I haven't tested how it works at high loads. Eg 12 kw coming from grid and 15kw load comes on.


Btw I don't limit my bms' in charge or discharge. Each bms can charge discharge 200 amps but with roughly 12kw of ac to work with the most any bms will ever see is about 60 amps.

The bms came with 25a charge and they gave me all kinds of headaches until i figured it out.

 

[Hedges]

SI should charge from generator when programmed input current allows, and invert from batteries to supply additional loads when that exceeds the input current limit.

We would like one SI to pass through 56A from generator (or grid) and invert another 6kW, 50A from battery, for 106A out of a single SI.

However, manual says to put OCP no greater than 56A on AC1. Now, I'm in the habit of having my (thermal) OCP 25% higher than the current I plan to draw, which would be 70A. But anyway, seems they didn't design the PCB traces to allow 106A.

Greater than 100A with two SI in parallel on same phase should be doable. At least if some of that comes from inverter. You probably can't get to 112A, exactly 56A each, passing through from generator because it won't split evenly. What breakers you use on input and output make a difference. Mine are pretty matched with Midnight/CBI magnetic-hydraulic breakers.

 

[1201]

I

How's the system working nowadays? Is it running smoothly?

 

[SilverbackMP]

How's the system working nowadays? Is it running smoothly?

Sorry for the late reply. I saw it pop up but forgot to reply.

Mostly like a top. It's kicked off power maybe three times for a second or two each time - and then restarted itself. A couple of times in the few weeks after it got up and going and then last night it did it too. Time before the last, the logs showed WrnExtBMSTmOut (which is W953) and LoBatMod1 (W756) and LoBatMod2.

It's not really that big of hinderance, except last night it did it right after I put my CPAP on and it will jack with any of my (small) servers that I will have setup...which includes security cameras and (a light usage of) home assistant....which are going to be on a upper tier synology (not rack mount, but the tier below that). I guess I need to get more serious about putting together a battery backup to my batteries.

 

[Hedges]

What causes it to drop and restart?

For cameras and routers, I would consider 12VDC, no inverter.

 

[SilverbackMP]

What causes it to drop and restart?

For cameras and routers, I would consider 12VDC, no inverter.

No idea of the cause...other than what's on the error logs. It's on my (quite long) to do list to investigate (probably fruitlessly).

 

[1201]

Sorry for the late reply. I saw it pop up but forgot to reply.

Mostly like a top. It's kicked off power maybe three times for a second or two each time - and then restarted itself. A couple of times in the few weeks after it got up and going and then last night it did it too. Time before the last, the logs showed WrnExtBMSTmOut (which is W953) and LoBatMod1 (W756) and LoBatMod2.

It's not really that big of hinderance, except last night it did it right after I put my CPAP on and it will jack with any of my (small) servers that I will have setup...which includes security cameras and (a light usage of) home assistant....which are going to be on a upper tier synology (not rack mount, but the tier below that). I guess I need to get more serious about putting together a battery backup to my batteries.

Darn. I wonder what's causing the errors . Maybe comm issue between bms and sunny island? I hope you get it perfect. Mine have been running non stop with no errors for over a month now

I'm still using vrla settings but it tends to stay fairly accurate as long as the batteries get charged to full every day.

 

[SilverbackMP]

Darn. I wonder what's causing the errors . Maybe comm issue between bms and sunny island? I hope you get it perfect. Mine have been running non stop with no errors for over a month now

I'm still using vrla settings but it tends to stay fairly accurate as long as the batteries get charged to full every day.

Yeah, it's gotta be a comms issue with the BMS. I might try changing some of the comms cable. Starting with the one from the master BMS. Judging from the second or two that power has gone out each time, it's not throwing the contactors open...so that's good. It's got to be the Sunny Islands doing a hot restart (I've seen them do the same thing when I was "recommissioning").

 

[1201]

Yeah, it's gotta be a comms issue with the BMS. I might try changing some of the comms cable. Starting with the one from the master BMS. Judging from the second or two that power has gone out each time, it's not throwing the contactors open...so that's good. It's got to be the Sunny Islands doing a hot restart (I've seen them do the same thing when I was "recommissioning").

Is getting rid of closed loop comms and option for you?

 

[SilverbackMP]

Is getting rid of closed loop comms and option for you?

I don't know if that would work with REC and seperate batteries with master/slave config? Never considered it.

 

[1201]

I don't know if that would work with REC and seperate batteries with master/slave config? Never considered it.

I don't know, it just feels like the closed loop comm is more trouble than it's worth- since you are ac coupled the sunny island has an accurate measure of what's going in and out and even when it diverges from the victron shunt the sunny island will tell you that it's soc is off, and even by how much

My current sunny island soc vs smart shunt

 

[westvandude]

https://diysolarforum.com/threads/sma-6048-rec-bms-soc-wrong-problem.80156/ Take a look at my thread where rec bms did weird stuff. Most of the way down are instructions on reseting the SOC when you think the pack is fully charged. It did do something weird where it did not connect to grid charging for 20-30mins and was drawing from battery for my critical loads panel. i went to look up what the hell was going on... came back to it checked voltages etc and everything was normal and it had grid connected to charge. Yes... too many settings on the sunny islands. But when they work they work good. I don't have a generator setup yet either. Just bought a 30A 120/240vac outside wall mount receptacle and 20ft cable need to get more cable to do the inside wiring and an ATS.

 

[westvandude]

REC balancing is tricky. When it's balancing the finned body of the bms gets quite warm/hot.... you can go into settings and select the max temperature allowed with the temp sensor in the bms. I lowered mine as it got quite hot I figured that's not great for the circuitry components inside the bms.

 

[SilverbackMP]

Fifth one just showed up.