diy solar

diy solar

Sol-Ark 15K in Operation--my thoughts on install and communication

kdub23

New Member
Joined
Jun 21, 2022
Messages
35
Hi All,

Last Friday, I put my Sol-Ark 15K into production. This was a retrofit into an existing 18kw grid-tied system. For now, I exclusively AC-coupled, but will reconfigure once my garage gets to a more palatable temperature to DC-couple the Sol-Ark with ~12kw of my capacity. I also got the 15K talking via MODBUS RTU. Here are my thoughts on installation/operation and some notes on speaking MODBUS.

IMG_5301.jpeg

INSTALLATION:
As mentioned, I AC-coupled for now, but will adapt in the future to allow myself the ability to preferentially choose what system I will use for PV inversion. With the 200-amp contactor, I ran my entire household through the 15K. This is teamed up with 5x SOK SK48v100 Rack Mount LiFePO4 batteries from the guys at CurrentConnected.
  • I mounted the Sol-Ark (all 138 lbs of her) ~6" over a 12"x12"x60" wire trough. I paper-traced the knockouts and transferred those down to punch out. I used EMT with set screw connectors. Even with ample 1-1/2" knockouts and (currently) no PV wire connected, the connection area gets tight. The ground and neutral bars need either crimped on ring connectors or lugs (what I used) to land those. This makes the right-hand side of the unit pretty congested. Sol-Ark went with a 1" knockout instead of 1-1/2" for the communications, so plan ahead if you don't have a partial stick of that laying around.
  • Some issues:
    • The manual (as discussed at length here on the forum) is not well done. Upon first flipping the disconnect, you're kinda left at a loss for what to expect from the unit, especially when your loads don't immediately turn on.
    • The protective film on the screen is amazingly hard to remove!
    • The plastic cover to keep your conductive little fingers from getting where they shouldn't be does not have a large enough cutout for the battery breakers. That means you can't secure it flush and it bows out right around those breakers. How do you miss that??
    • If you use 4/0 battery cable like me, getting both through the toroids was a little difficult.
    • Adding the WiFi/Ethernet dongle and setting up the app is cumbersome at best. The app asks for your address and phone number and that's a big ole nope from me, especially noting that I had to allow previously blocked connections to/from China through my firewall to get the dongle to work.
    • Updating firmware for the Sol-Ark was painless, but it's a weird process. You request it from their site and a nice support engineer reviews that request and pushes that firmware to you. I checked the box for automatic updates during that process before I realized that when the firmware update is applied, the inverter restarts and cuts power to your loads!
    • The fan is louder than I expected. It also comes on randomly in my hot garage even though it is not performing any meaningful DC-to-AC conversion. It doesn't come on in the morning when the garage is cooler.
  • My SOK batteries are awesome. They immediately communicated with the Sol-Ark with no fuss. Straight ethernet cable and one settings change, and you're speaking CanBus. As you can see in my picture, the battery lugs are not only prominently presented, but also uncovered. An errant brush with a shovel or weedeater shaft, and some sparkies will ensue. I've 3D-printed off some battery lug covers, but still tweaking a few dimensions on those.
  • Overall, it's impressive what this hunk of electronics they call the 15K can do. Failover to battery involves the slightest flicker from your lights. Anything with capacitors will not even realize the power is no longer coming from the grid. It successfully started (albeit with some strain) my 4-ton upstairs A/C while running the downstairs heatpump and the rest of the house. Impressive indeed. Grid-tying was painless, although the 5-minute countdown from my Sunny Boys will get annoying.
COMMUNICATION:
  • The PVPro app is better than I expected, but as mentioned several times before, being so reliant on the PRC for data/apps is a big turnoff. Politics aside, I'd rather have faith that even my seemingly innocuous data is staying safe. Yes, there is only a 5-minute refresh rate, but more on that in a second.
  • With a lithium battery in place, you can speak MODBUS RTU over half-duplex RS-485. Since I already had a WattNode Modbus in my main panel, I can easily daisy chain the Sol-Ark with my WattNode and let the datalogger poll both of them. The Sol-Ark supposedly cannot change its address to anything other than 1 unless in a parallel application. Using the Modbus document posted on these forums, I was able to rapidly communicate and pull data from the Sol-Ark.
  • Most parameters update every second, however, totals seem to update every 5 minutes which may tie to the app update interval.
  • The Sol-Ark totals differ slightly from my SMA and WattNode readings. I've verified the SMA and WattNode to being damn-near revenue grade, so I'm thinking accuracy isn't the highest with the Sol-Ark, but time will tell when I get my analytics and dashboard built.
Let me know if you guys have any questions or want to see anything else. Appreciate all the advice I got on here before embarking on this install. I've still more things to play with, but so far I'm pretty happy with what I've done.
 
Check out Solar Assistant for a quality alternative to the sol-ark apps. You may want to change the wiring to your batteries. You should pull positive and negative from opposite ends of your pack. For example, you could pull the negative from the bottom battery and positive from the top battery in your assembly. I believe Will Prowse had a video covering battery connections within the last 1-2 months.
 
Check out Solar Assistant for a quality alternative to the sol-ark apps. You may want to change the wiring to your batteries. You should pull positive and negative from opposite ends of your pack. For example, you could pull the negative from the bottom battery and positive from the top battery in your assembly. I believe Will Prowse had a video covering battery connections within the last 1-2 months.
I feel you on the battery connections. But I've oversized with 4/0 and my vanity likes the look better. Efficiency losses are negligible.
 
Great looking install, and TY for your detailed thoughts!

I agree with you about your concerns with having you info given to China. It's my understanding that SA is actively working on bringing this inhouse domestically. Hopefully this happens within the next year.

I'm pleasantly impressed the SA was able to start the 4 ton AC (without a soft-start) given it had additional loads as well. You may still want to add the soft-start to reduce the strain, but that's still impressive given it's a HF inverter!

I would also agree with considering redoing your battery connections. Your cables look very clean, but you will certainly be taxing the upper battery(s) more heavily than the bottom battery(s). Connecting the main positive and negative at the second and forth batteries respectfully would probably be much better for more even utilization, but at the cost of visually being not quite as "clean". Functionality would be my main priority in this regard, but that's obviously your call.

Again, nice job and thanks for your thoughts on the inverter/system, it should be really impressive once the additional DC arrays are added!
 
I would also agree with considering redoing your battery connections. Your cables look very clean, but you will certainly be taxing the upper battery(s) more heavily than the bottom battery(s). Connecting the main positive and negative at the second and forth batteries respectfully would probably be much better for more even utilization, but at the cost of visually being not quite as "clean". Functionality would be my main priority in this regard, but that's obviously your call.!
With my battery cable gauge, the design of the SOK’s terminals, and the fact that all my BMS’s are communicating, I’m skeptical it makes that much difference. Not to mention, they’ll be used primarily as a whole-home backup not daily drivers.

BUT, I’ve got dataloggers coming out of my ears, so I’m going to hook one up to the RS232 port of the battery bank and log data on charge/discharge. I’m super curious now.
 
Yes, thank for your review.

I've been wanting to add some input to questions I've seen here, but haven't had the extra time.

The Sol-Ark info I read on page 4, was saying that the Modbus RS-485 hadn't been activated yet, so I didn't search any farther. I'll add that to my list.

I have a 4 ton geothermal open loop (240v well pump comes on 1st) system that is running on the 15k. It can be a little harsh starting, if other things are also running. I'll be installing a soft start to make it play well with others in the near future.

I like the Pro PV especially for getting my breaker panel balanced. After watching the logs, I learn to recognize different loads (240 or 120v) and which ones alternate and or run at the same time (washer/dryer). Solar Assistant doesn't show the L1/L2 separately or the 3rd MPPT. As for that info being watched by others, let's just say, "I can tell when the wife is home and what she's doing".

Thanks again, hope we can all get the most from our systems.
Brian
IMG_20220731_112304.jpg

More pix
 
I like the Pro PV especially for getting my breaker panel balanced. After watching the logs, I learn to recognize different loads (240 or 120v) and which ones alternate and or run at the same time (washer/dryer). Solar Assistant doesn't show the L1/L2 separately or the 3rd MPPT. As for that info being watched by others, let's just say, "I can tell when the wife is home and what she's doing".

More pix
Powerview Pro (Web Version) is really a well written piece of software. I suspect that not many Sol-Ark owners have dug into it to see how powerful it really is. I think I counted 69 Parameters that can be graphed 6 at a time on an overlay and it keeps all the data saved from day one.

I shaved of at least 10% of extra grid usage just by studying the graphs and tweaking the TOU and then seeing the results after a week then tweaking further and further until every last drop of power that can offset the grid is used while still keeping me safe from a blackout.
 
With my battery cable gauge, the design of the SOK’s terminals, and the fact that all my BMS’s are communicating, I’m skeptical it makes that much difference. Not to mention, they’ll be used primarily as a whole-home backup not daily drivers.

BUT, I’ve got dataloggers coming out of my ears, so I’m going to hook one up to the RS232 port of the battery bank and log data on charge/discharge. I’m super curious now.
I think the results might surprise you. With a constant load, you'll see it with a clamp comparing the top of your stack to the bottom. Please share your findings when you get a chance to look at it... Since it's easy to do, you might want to compare your findings to hooking them up on #2/#4 as I suggested as well.
 
Last edited:
Yes, thank for your review.

I've been wanting to add some input to questions I've seen here, but haven't had the extra time.

The Sol-Ark info I read on page 4, was saying that the Modbus RS-485 hadn't been activated yet, so I didn't search any farther. I'll add that to my list.

I have a 4 ton geothermal open loop (240v well pump comes on 1st) system that is running on the 15k. It can be a little harsh starting, if other things are also running. I'll be installing a soft start to make it play well with others in the near future.

I like the Pro PV especially for getting my breaker panel balanced. After watching the logs, I learn to recognize different loads (240 or 120v) and which ones alternate and or run at the same time (washer/dryer). Solar Assistant doesn't show the L1/L2 separately or the 3rd MPPT. As for that info being watched by others, let's just say, "I can tell when the wife is home and what she's doing".

Thanks again, hope we can all get the most from our systems.
Brian
View attachment 106331

More pix
That’s a lot of batteries! Do they cycle up/down in unison as they charge/discharge? In other words, do they all maintain equivalent SOC?
 
The Sol-Ark info I read on page 4, was saying that the Modbus RS-485 hadn't been activated yet, so I didn't search any farther. I'll add that to my list.
From my testing, if you have your Sol-Ark set to Lithium Battery Mode 00, then it is in CanBus mode. This frees up the RS485 wire pairs to communicate via Modbus. If your batteries are speaking ModBus, then I believe those pairs are used up and allocated to speaking back and forth to the battery. The RJ45 port labeled ModBus on the 15K does work, but after a short amount of time stops returning values and only returns zeros when you poll Modbus registers. This is absurdly weird behavior, and I can't rationalize it. The CanBus port, however, still uses pin 1,2 and 7,8 to speak ModBus via half-duplex RS485 and pin 4,5 are speaking CanBus to the batteries. Ground is not needed for RS485.

So, I've followed the advice on the solar-assistant help page and just split an ethernet cable in two and am reading RS485 with one while the other connects to my SOKs. Works like a charm.
 
So, I've followed the advice on the solar-assistant help page and just split an ethernet cable in two and am reading RS485 with one while the other connects to my SOKs. Works like a charm.
Unfortunately it only works if you have the Lithium Battery setting set to 00.
Any of the compatible closed loop batteries require a setting other than 00 but SOK and EG4 will work with 00.
 
Hi All,

Last Friday, I put my Sol-Ark 15K into production

Let me know if you guys have any questions or want to see anything else.
suggestion: move either the red OR the black cable between the batteries & inverter from top to bottom.
Currently you are using your top battery more then the ones underneath
By moving _one_ of the supply cables to the bottom you will use all batteries at the same rate.
 
Unfortunately it only works if you have the Lithium Battery setting set to 00.
Any of the compatible closed loop batteries require a setting other than 00 but SOK and EG4 will work with 00.
I assume in any other mode, the Sol-Ark becomes a Modbus Master and therefore does the polling and cannot be polled as a slave device. Unfortunate. (And also one of the reasons I chose SOK.)
 
suggestion: move either the red OR the black cable between the batteries & inverter from top to bottom.
Currently you are using your top battery more then the ones underneath
By moving _one_ of the supply cables to the bottom you will use all batteries at the same rate.
Yup. Discussed at length already here. I have a theory the communicating BMSs compensate for the increased resistance in my (aesthetically more appealing) setup by balancing current. I’ll run some tests with my dataloggers and report back.
 
I saw this thread and thought of the discussion here.
 
Yup. Discussed at length already here. I have a theory the communicating BMSs compensate for the increased resistance in my (aesthetically more appealing) setup by balancing current. I’ll run some tests with my dataloggers and report back.

My bet is little to none, if you draw high current. Any balancing (passive, burn off through a resistor?) will be small. I doubt they communicate anything about balancing between batteries.

Above the knee, they may track pretty well. Below the knee, I expect high currents to have significant draw from different batteries. Try a clamp ammeter around each segment of cable, determine how much goes into each battery. Then draw from diagonally opposite ends (like Spunky's) and see what the difference is.
 
My bet is little to none, if you draw high current. Any balancing (passive, burn off through a resistor?) will be small. I doubt they communicate anything about balancing between batteries.

Above the knee, they may track pretty well. Below the knee, I expect high currents to have significant draw from different batteries. Try a clamp ammeter around each segment of cable, determine how much goes into each battery. Then draw from diagonally opposite ends (like Spunky's) and see what the difference is.
I did quite a bit of testing once I deciphered the SOK serial protocol. And I was giving too much credit to the BMS. No balancing that I can tell. Top battery (master in my case) was receiving the largest current with a clear downward trend the further away from the SolArk connection. I’ve just been too busy to put it all in chart form.

My positive cable is now on the second batt from the bottom, and the negative is on the second batt from the top. All batteries now charge/discharge within 2-3A of each other.
 
"balancing" by BMS would be equalizing voltage between cells within a single battery. You should be able to read cell voltages from it.

Diagonal corners should be perfect for two batteries, not exactly perfect for more. If yours discharge within a couple percent of each other, should be good enough. Was that in the flat part of the curve? I'd expect it to balance out SoC at the top and bottom knees (currents diverging as needed to maintain similar voltage).
 
Back
Top