Sunny Island 6048 Midnite Classic Rec BMS

[G00SE]

So I’ve been PMing with @Hedges a bit about SMA systems. Very grateful for the contributions and I think I’d like to expand to others for more insight as well.

SMA Sunny Island does not seem designed to handle Lifepo4 banks. To mitigate, it appears that many utilize the REC BMS for lithium comms
Every thread I’ve found so far, shows this working with AC coupling with Sunny Boy.
Hedges brought up the sunny boy as well, so I guess maybe I need to take this under more serious consideration
Unfortunately, my pea brain can only absorb so much, so often. And so it’s still stuck on DC coupled systems

My thought was 2x SI 6048 with 2x midnite classic charge controllers. Midnite has a communications adapter to allow SI and classics to communicate.

What I can’t seem to find is, will this design integrate with the REC BMS? SI + midnite + rec = success?

Secondly, would the midnite classics be the most logical choice due to the comms adapter or is that not necessarily relevant if the BMS communicates via CAN with the inverter. How does it communicate with the charge controller at that point?

 

[Hedges]

SI + midnite + MNSICOMM + rec should be good. With or without SB.
In addition, a generator should work, if it is reasonably well behaved (monotonic sag of RPM/frequency with load.)

https://files.sma.de/downloads/SIGEN-11FD1212.pdf

Sunny Island does not have charge settings for lithium (may have had at one time.) It does support communication to supported BMS, which allows not only suitable voltage based on 16 x LiFePO4 (or other chemistry) voltage, but also when BMS detects cell voltage divergence, charger parameters can be reduced to let balancer keep up.

files.sma.de/downloads/SI-LiIon-TI-en-48.pdf

This does not mention the REC BMS some use for DIY, and I think there may be one other brand. What it does list is commercial batteries. BYD is one of them. When I looked up prices for a different high-voltage battery & inverter, BYD was about 2x the cost of cheap server rack batteries, which in turn are 2x the cost of DIY with 280 Ah cells.

Depending on quantity and model of SI, and size of battery, various model batteries are recommended or not.

Besides operating with SI, decide if you want a UL listed ESS, which means that specific inverter and battery were tested together.



If not using BMS communications, SI would be configured for VRLA to set max and min voltages. It may not make a good estimate of SoC. Configured for 48V nominal VRLA (24, 2V lead-acid cells), the max and min voltages do not match up to 16s LiFePO4. I think it is 46V nominal VRLA which does match, but figure out the per-cell VRLA settings which hit the voltage you want.

With Midnight Classic or any other SCC not communicating with SI (or DC coupled loads), you need a battery shunt so SI can see current. That will help it control charging from grid/generator input or AC coupled PV.


MNSICOMM is the adapter which interfaces Sunny Island to Midnight Classic, allowing SI to read current and set voltage. It also reads PV voltage, watts, etc. It does not control current. It emulates Sunny Island Charger.

MidNite Solar MNSICOMM Communication Adapter

Shop MidNite Solar MNSICOMM Communication Adapter online or call us, Solarflexion, at 800-942-2424 for your solar needs.

www.solarflexion.com

https://files.sma.de/downloads/SIC50-IA-en-11W.pdf

It works with earlier SI firmware but not more recent. Sponge Bob indicated it was broken in 2021. I have used SIC40 with SI 5048US but haven't tried with SI 6048US from DC Solar.

Schneider xw pro 6848 not powering up with eg4 lithium battery

Beats me, but here's a list of some dozens of batteries that speak a common language: https://files.sma.de/downloads/SI-LiIon-TI-en-45.pdf Thanks ! The document doesn't necessarily say they speak any language (maybe German) but I'm sure they DO speak the common language of D.C. I didn't...

diysolarforum.com

A number of DC coupled and AC coupled Sunny Island systems are featured here. I heartily recommend using Sunny Boys configured for off-grid/Island when adding PV to an off-grid or generator-as-grid SI system. If not backfeeding grid SB total wattage can be up to 2x SI wattage, 24kW AC coupled PV on a 12kW SI system. If backfeeding grid, SB wattage limited by 56A relay to 6.7kW per SI, and SB should be configured for Rule-21 (which may or may not have issues) for UL-1741-SA/SB or earlier UL-1741 models configured for Backup.

https://files.sma.de/downloads/SISYSGUIDE-KEN140421.pdf

DC coupling should be OK too, but SCC will deliver what current they want. At least for lead-acid which prefers a particular charge current, SI will regulate any AC coupled PV so its battery charging hits that current (when added to any DC coupled it knows about.) Similarly Midnight Classic + Whiz Bang Jr, or Victron + Cerbo + Shunt should do the same. Lithium can generally take more current, but if operated near freezing you may want to set a reduced charge current.

It is nice to have a system with oversized PV array and oversized SCC (or GT PV) capacity which supplies all power needed for loads and regulates charge current to target. My SI/SB/AGM system has enough PV to charge at 0.6C but limits it to 0.2C.

 

[G00SE]

Thank you again for the plethora of contributions.
My initial set up will be roughly 12 panels on top of a cargo trailer (2 stacks of 6 panels with one “layer” coming out as an awning)
My 32-305ah cells should be here tomorrow. Which I think has really kicked me up in gear on the realities of a system that can intercommunicate as needed as I have not yet ordered a BMS for these cells.
Being that I am looking at a roughly 4800w array, 30k of battery on/in an insulated cargo trailer I had no intention of ever grid connecting.
At most I would connect a 120v inverter generator that I figured would most easily be used with a chargeverter to the batteries.

I will continue to research the Sunny boy options against my minds wishes ?

 

[Hedges]

Cargo trailer - will this be mobile?
2x SI is 280 lbs, and that steel box adds a lot more.

What do you need to power? An HF transformerless inverter could be better for mobile.
There are cheap imports, of course. Also good brands. I think Outback has HF. Don't know about Victron. Midnight Rosie is new but should be very good.

If you do use SI, should be able to feed a small generator through it because it supports load with current from batteries. The nicely behaved frequency vs. load response matters if SB is feeding in. SI by itself I think is tolerant of wide voltage/frequency range.

When lithium battery is connected to any inverter with significant capacitor bank, needs precharge circuit to limit inrush, which is otherwise enough to trip BMS, blow class-T fuse, weld contactors. Maybe HF inverter doesn't have that issue if 60/120 Hz ripple comes from HV caps.

Lots of guys here have manual precharge circuits. REC offers precharge module. Note that for SI, decoupling capacitors are after SI's breaker, so order of closing breaker and performing precharge needs to be correct.

If adding 5kW to 20kW of PV, Sunny Boy would be an economical option and adds AC wattage available during the day. For a ground-based installation, it also allows PV on distributed buildings away from the battery. If virtually all PV production goes to battery and AC loads aren't present during the day, then less value, maybe the case for your trailer. It is a good fit for a system with heavy A/C or water pumping loads during daytime.

DC coupled with SI especially makes sense if single SI 120V system is all that is needed.

 

[G00SE]

I will be using it to power the construction of my home as well as my well pump.
It will be able to be mobile, but will not move with regularity.
If I run a pair of SI + a 30kwh bank + a dozen panels I’m looking at probably adding 1500lbs to the trailer. My current dilemma is floorplan as I would prefer not to have all of the battery and inverter weight on one wall, but also don’t want to run lengthy battery cables that multitask as tripping hazards.

Frankly, I’d do this same build with a pair of schneiders, radians, Multiplus or Rosie’s, if they were all over eBay for 1500 each like the SMAs.
But they aren’t
The reality is for me, it seems, that I either figure out how to make a SI based system fit my needs, or I abandon the tier 1 ideas and just throw a 10kw SRNE unit inside instead.
I am apprehensive to go this route due to lack of known long term durability and inrush current on inductive loads. (Such as my 460ft deep 1.5hp well pump)
Based on @42OhmsPA experience with his, it’s an intriguing budget option. I had initially settled on the 12kw Growatt but between the issues of random failures (although main boards are easily acquired and replaceable) runaway batteries due to their archaic SCC, overheating due to non toroidal based transformers, and 150+ watts of idle, I think the SRNE would be a better fit. The twin eg4 6500 with load center was appealing but people can’t seem to run away from their inverters fast enough
But once my house is built I would like to reconfigure my inverter and battery base for my permanent home solution (hence starting with a pair of SI in a cargo trailer)

 

[Hedges]

SI manual allows surprising long battery cables. You could route those through floor and under the trailer.
Twist +/- cables together for low inductance.

Can cells tuck up under frame of trailer? Or not with recommended orientation?

For the final system, having SB for additional panels will be nice. 2x SI surge to 22 kW at 240V, should be able to start 4.4 kW induction motor. Then SB ramps up to carry possibly the entire load and charges batteries, leaving SI's surge ability ready for next load. Up to about 12kW SI + 24kW SB = 36kW operating load, peaking at 46kW for 3 seconds.

SI's derating with temperature is documented in manual. 6048US doesn't derate nearly as much as 4548US. SB however delivers full wattage up to higher temperature.

Definitely SI is the way to go compared to cheap HF inverters.

You might want to eventually get an auto-transformer. That could help to some extent with balancing phases. It would also let the system continue operating if one SI goes down, providing redundancy. I plan to implement eventually in order to reduce no-load current (with the feature of sleeping some SI until load increases, split-phase is lost of only one SI running. On the flip side, one SI delivering 6kW has greater loss than 2x SI each delivering 3kW. Haven't looked into switch point to enable additinal SI.)

 

[G00SE]

Welp. I guess we will find out soon. My cells will be here Friday. I’ve got 2 EEL boxes with 2-200a seplos BMS in the mail as well. I’ve seen “some” success with these using pylontech selections so I may fiddle with this. Worst case I sell the seplos, use the case, and buy the REC

I’ll be driving next Saturday to pick up 2 SMA SI 6048s and then it’ll be go time!

I sent an email to REC last night to see if they have customers currently set up how I intend to
They replied at 6am this morning saying they are going to investigate today! That’s awesome customer service.

@HighTechLab is listed as a REC vendor on the rec website, but the current connected site only shows the Victron configuration.
Dexter, do you have the SMA version of this BMS?

 

[HighTechLab]

Dexter, do you have the SMA version of this BMS?

Only difference is a firmware update. You can contact REC for this, and you will need to provide your serial number.

Please note I have not read the entire thread, only post 7...super crazy tuesday!

 

[G00SE]

Only difference is a firmware update. You can contact REC for this, and you will need to provide your serial number.

Please note I have not read the entire thread, only post 7...super crazy tuesday!

Thanks for the info I may be emailing about this
In regards to the rest of the thread, no worries it’ll probably bore you lol.

 

[Higher_wire]

We're installing LFP packs into DC Solar trailers to replace dead lead, using REC. Depending on configuration they have one or two Sunny Islands with Midnite controllers. REC have helped us get up and running, since SI's can be a pain if comms aren't going smoothly.

The new 2Q BMS has a precharge circuit prewired and communicates with SMA out of the box using a prewired cable. The only downside is the need for wifi module to change BMS parameters.

 

[jmm]

So I’ve been PMing with @Hedges a bit about SMA systems. Very grateful for the contributions and I think I’d like to expand to others for more insight as well.

SMA Sunny Island does not seem designed to handle Lifepo4 banks. To mitigate, it appears that many utilize the REC BMS for lithium comms
Every thread I’ve found so far, shows this working with AC coupling with Sunny Boy.
Hedges brought up the sunny boy as well, so I guess maybe I need to take this under more serious consideration
Unfortunately, my pea brain can only absorb so much, so often. And so it’s still stuck on DC coupled systems

My thought was 2x SI 6048 with 2x midnite classic charge controllers. Midnite has a communications adapter to allow SI and classics to communicate.

What I can’t seem to find is, will this design integrate with the REC BMS? SI + midnite + rec = success?

Secondly, would the midnite classics be the most logical choice due to the comms adapter or is that not necessarily relevant if the BMS communicates via CAN with the inverter. How does it communicate with the charge controller at that point?

 

[Hedges]

SI has communications with REC BMS, or whatever is in their approved battery list.

With interface to Midnight Classic, SI can request a particular charge voltage. But it can't regulate charge current.
I don't know if SI tries to regulate current as requested by BMS, or only voltage. So I don't know if Classic can work as well as Sunny Boy. Or maybe better, since several seconds are required for frequency shift to control Sunny Boy.

Newer SI firmware breaks communication with classic. Only earlier firmware will work.

You could also look into whether Midnight Classic provides closed-loop communications with BMS.

 

[toms]

I use the REC to switch a gigavac minitactor between the PV and an outback flexmax. This method will work with any solar charge controller.

The REC will still balance cells and communicate with the SI, it won’t command the midnite classic, but you can use sensible charge setpoints and know that if a cell goes high the charger will be stopped by the REC, but you won’t lose power to the inverter.

You can also connect a generator to the SI as per the manual and the REC will command the SI to open the generator relay as required.

I use a REC / SMA combo with DC / AC / direct generator, and 240V - 48V DC charger, the REC can be set up to handle it all.