Sol-Ark SOC tracking issues

[Cmiller]

Any company that says it's inverter will stay calibrated more than three days in open loop mode is probably just trying to create sales or is using very conservative DOD amounts in their calculations or is basing it on an ideal installation. There is just no way for the Inverter can know the state of the Individual packs!

Unless you got a perfect Install and perfectly matched packs so that all the packs are charging and discharging evenly the packs will start to drift apart quickly under partial charging.
Look at any of Will's videos where he measure the Amps going to the individual Packs and you will see numbers like 18A into one pack and a low of like 16A into another pack. By the end of a partial charge the pack that got 18A may be at 70% SOC while the one that got 16A will be at around 65% SOC.
The next night you drain the packs down to 20% according to the Inverter and the 18A one will actually be above 20% and the 16A one is actually nearer to 15%.
Repeat that same amount of charge the next day and the first one will be closer to 72% and but the second pack is now closer to 60%.
You can see where this is going and the difference between packs is going to show up in the coming days as a sudden drop in SOC as the lowest batteries start to drop the combined voltage.
People who run with Wide Margins won't have this issue as quickly but the more you try to squeeze power out of the packs is the quicker it will happen.

In closed loop this does not happen because it uses the Average of the True SOC of each pack.

A few points......

1. Average of true SOC of each pack= pack 1 SOC+ pack 2 SOC + .......... total divided by number of packs. This number will be exactly equal to the NET AVERAGE total AH in vs AH out of the battery bank..... therefore using a shunt to track this will get the EXACT SAME RESULTS! This is of course assuming that you are calculating in efficiency losses etc. Bottom line is, if you have say a 30kw bank of batteries and you remove 20kw, then charge 10kw back in, you will be at a 20kw net, which is 66.66%. You obviously have to calculate losses in, but if you have a shunt that is literally tracking AH in and out of the bank IT DOES NOT MATTER THE IMBALANCE OF THE INDIVIDUAL BATTERIES!!!!! Your NET AH/KWH/COLUMBS what ever unit you wish to use, WILL equal the average of the batteries! Otherwise you would be losing power to thin air..... AH in-AH out = net!
2. Explain to me why I see other brands of battery monitoring devices tracking accurately!? Here is a list of brands that I HAVE SEEN WITH MY OWN EYES TO WORK!!!! Victron, Schneider, Outback, Midnite, Magnum, Tri-metric...... each one of these I have literally personally set up and used with LFP batteries in open loop and seen to accurately track SOC out to probably 1.5 to 2 weeks of not getting fully charged! After 2 week it's a gamble! I know eventually they run off, but NOT IN 3 DAYS!!!!
3. Another note.... because of the internal cell voltages in an LFP battery, your "spread" in SOC between batteries in parallel will limit itself to a certain amount of difference! The reason being that the further the difference in true SOC, the further the voltage difference. Therefore the lower unit/units WILL charge from a higher unit/units. I would guess you probably wouldn't ever see more than maybe 20% spread absolute max! Anything more than that WILL BE an inaccuracy of the BMS! It is simply impossible to have 2 LFP batteries connected in parallel at let's say 20% true SOC and 80% true SOC!
4. But really though..... what difference does variation in SOC between packs make in the overall SOC? Overall SOC is the net average anyway..... doesn't matter if the batteries figure out the average between packs, or if an external shunt based system tracks the average.... The inverter DOES NOT NEED TO KNOW THE STATE OF INDIVIDUAL PACKS!!!!!

But all of this aside. How can this inverter be used off-grid in Ohio running in open loop SOC mode, when during the winter you end up not getting fully charged for a week or more?? To say you just need to charge up with a gen every 3 days is not even remotely plausible!

At the end of the day the Sol-Ark SOC tracking algorithm is far, far, far from being practical to use! And when compared to other brands it doesn't hold a candle next to the others! So the question remains, why do they falsely advertise having a shunt "for accurate SOC% monitoring"??

 

[robby]

A few points......

1. Average of true SOC of each pack= pack 1 SOC+ pack 2 SOC + .......... total divided by number of packs. This number will be exactly equal to the NET AVERAGE total AH in vs AH out of the battery bank..... therefore using a shunt to track this will get the EXACT SAME RESULTS! This is of course assuming that you are calculating in efficiency losses etc. Bottom line is, if you have say a 30kw bank of batteries and you remove 20kw, then charge 10kw back in, you will be at a 20kw net, which is 66.66%. You obviously have to calculate losses in, but if you have a shunt that is literally tracking AH in and out of the bank IT DOES NOT MATTER THE IMBALANCE OF THE INDIVIDUAL BATTERIES!!!!! Your NET AH/KWH/COLUMBS what ever unit you wish to use, WILL equal the average of the batteries! Otherwise you would be losing power to thin air..... AH in-AH out = net!

Yes the same amount of Amps are being put into the whole bank but it is almost always going to be fed into the batteries unevenly.
I think we can all agree that some packs will be charging at 18 Amps and others at 16 Amps etc.
The problem is that their is a relationship between SOC and Voltage under load. The Battery that Dips down to 10% SOC has a lower voltage approx (48V) and starts to drag down the packs that are at 25% SOC (51.4V).

1. Explain to me why I see other brands of battery monitoring devices tracking accurately!? Here is a list of brands that I HAVE SEEN WITH MY OWN EYES TO WORK!!!! Victron, Schneider, Outback, Midnite, Magnum, Tri-metric...... each one of these I have literally personally set up and used with LFP batteries in open loop and seen to accurately track SOC out to probably 1.5 to 2 weeks of not getting fully charged! After 2 week it's a gamble! I know eventually they run off, but NOT IN 3 DAYS!!!!

As I said if the Charging and Discharging is even across the Packs then the amount of days before an imbalance will be a lot longer.
Did you measure the Current going In and Out of each of the Packs when you used those other systems?
Sol-Ark is simply giving you a Worst case scenario because then people won't bitch if they are at least getting 3 days of Partial charging with Open loop and a poorly balanced battery bank.

1. Another note.... because of the internal cell voltages in an LFP battery, your "spread" in SOC between batteries in parallel will limit itself to a certain amount of difference! The reason being that the further the difference in true SOC, the further the voltage difference. Therefore the lower unit/units WILL charge from a higher unit/units. I would guess you probably wouldn't ever see more than maybe 20% spread absolute max! Anything more than that WILL BE an inaccuracy of the BMS! It is simply impossible to have 2 LFP batteries connected in parallel at let's say 20% true SOC and 80% true SOC!

I would agree with that. I have never let it get past around 10-15% because of the potential of it reaching 20% difference and then my Inverter shutting down at an average of 20%SOC and carrying some of my less charged packs down to an actually reading of 0% SOC or worst.

1. But really though..... what difference does variation in SOC between packs make in the overall SOC? Overall SOC is the net average anyway..... doesn't matter if the batteries figure out the average between packs, or if an external shunt based system tracks the average.... The inverter DOES NOT NEED TO KNOW THE STATE OF INDIVIDUAL PACKS!!!!!

See the above Reply. Yes it does need to know the state of the individual packs or the risk is that some packs will be drawn down to too low of a SOC (repeating myself a lot lol). I see these issues with my Battery Hub, it shows each packs SOC. If your not really monitoring this stuff then you will not know that a problem is happening until you get a sudden drop in SOC as the lower SOC packs are used up.

But all of this aside. How can this inverter be used off-grid in Ohio running in open loop SOC mode, when during the winter you end up not getting fully charged for a week or more?? To say you just need to charge up with a gen every 3 days is not even remotely plausible!

Hence why almost all of the companies are telling you to use closed loop.
But more specific to your question is how is this house in Ohio going through consecutive Winter days with not enough Solar to charge the batteries? There must be generator usage going on or they are using an enormous battery bank and using more than what they can put back with PV.

Power is Power, if you dump in 15KW/h from the generator to get the batteries up to a 100% then you can shutdown the Generator earlier and use back most of that 15KWh at night

At the end of the day the Sol-Ark SOC tracking algorithm is far, far, far from being practical to use! And when compared to other brands it doesn't hold a candle next to the others! So the question remains, why do they falsely advertise having a shunt "for accurate SOC% monitoring"??

Your best bet is to stick with the Inverter that works for your purposes. The Sol-Ark is probably not a good fit for your Open Loop system.

 

[BajaDave]

I have a Solark 15 K and a Victron BMV 712.

The Victron is much more accurate at tracking SOC. So was the Growatt that I had prior to this new inverter. All three systems use a shunt to measure net power.

So I think a simple way to put this question is: why didn’t Solark invest a bit more engineering resources in using well-known technology to increase the accuracy of their own internal SOC implementation? Clearly it’s not that hard to do.

I have a grid tie system with expensive and unstable power in Mexico. my goal is to minimize grid consumption. A few cloudy days, and my SOC starts to wildly diverge from the Victron unit, putting me at risk of over discharging my batteries or shutting down the inverter. I have two choices: fully charge batteries every night from the grid to prevent this drift, or manually charge them by constantly monitoring drift.

neither solution is great. in the absence of an accurate SOC calculation, an option to force a generator/grid recharge on some interval other than every day would be great.

 

[robby]

I have a Solark 15 K and a Victron BMV 712.

The Victron is much more accurate at tracking SOC. So was the Growatt that I had prior to this new inverter. All three systems use a shunt to measure net power.

So I think a simple way to put this question is: why didn’t Solark invest a bit more engineering resources in using well-known technology to increase the accuracy of their own internal SOC implementation? Clearly it’s not that hard to do.

I have a grid tie system with expensive and unstable power in Mexico. my goal is to minimize grid consumption. A few cloudy days, and my SOC starts to wildly diverge from the Victron unit, putting me at risk of over discharging my batteries or shutting down the inverter. I have two choices: fully charge batteries every night from the grid to prevent this drift, or manually charge them by constantly monitoring drift.

neither solution is great. in the absence of an accurate SOC calculation, an option to force a generator/grid recharge on some interval other than every day would be great.

Because Sol-Ark and every other major Inverter company have moved to close loop communications.
The battery manufactures also want their batteries connected Via Closed Loop.

 

[BajaDave]

Because Sol-Ark and every other major Inverter company have moved to close loop communications.
The battery manufactures also want their batteries connected Via Closed Loop.

I guess I'm out of the loop then. The components for this system were selected by my local installer, and that's what was available. Hard to sneak 42kw of batteries over the border. But the last time I built a system myself in 2019, there were so many bugs in the inverter/battery communication process that most systems were built open loop. And people that started closed loop with approved batteries switched to open loop due to bugs. Sounds that like is changing, and I shouldn't expect Sol-ark to fix this any time soon. That does seem to rule out tons of battery options.

 

[robby]

I guess I'm out of the loop then. The components for this system were selected by my local installer, and that's what was available. Hard to sneak 42kw of batteries over the border. But the last time I built a system myself in 2019, there were so many bugs in the inverter/battery communication process that most systems were built open loop. And people that started closed loop with approved batteries switched to open loop due to bugs. Sounds that like is changing, and I shouldn't expect Sol-ark to fix this any time soon. That does seem to rule out tons of battery options.

Yes it started really changing fast about 18 months ago.
You do have one cheaper option which is to just change the BMS systems in each of your packs to something that works with the Sol-Ark.
I would call them and find out the various BMS options they recommend for the size cells that you have.
Of course the physical size of a BMS that can fit and the wiring harness etc would require research and the installation is going to be very time consuming.

 

[Cmiller]

I have a Solark 15 K and a Victron BMV 712.

The Victron is much more accurate at tracking SOC. So was the Growatt that I had prior to this new inverter. All three systems use a shunt to measure net power.

So I think a simple way to put this question is: why didn’t Solark invest a bit more engineering resources in using well-known technology to increase the accuracy of their own internal SOC implementation? Clearly it’s not that hard to do.

I have a grid tie system with expensive and unstable power in Mexico. my goal is to minimize grid consumption. A few cloudy days, and my SOC starts to wildly diverge from the Victron unit, putting me at risk of over discharging my batteries or shutting down the inverter. I have two choices: fully charge batteries every night from the grid to prevent this drift, or manually charge them by constantly monitoring drift.

neither solution is great. in the absence of an accurate SOC calculation, an option to force a generator/grid recharge on some interval other than every day would be great.

You nailed it!

It is beyond my comprehension why Sol-Ark would not want their SOC tracking to work better.

Well, actually though, it seems like they simply don't care, to be honest. Maybe because of the insane growth their company had, just because of nobody else having a proper all-in-one option available. I honestly think most Sol-Ark's get installed in grid sell with battery backup scenarios, and people literally are not working these backend functions that Sol-Ark says they have...... and they do..... sort of.... albeit glitchy.

But, what really yanks my chain is the fact that they keep on insisting that their SOC tracking does indeed work, when that is simply not the case!

Just today we just got done swapping out a 1,000AH battery bank (Ark batteries with very minimal deviation of SOC between the 5x 200AH units!) for the new Rubix GigStack batteries so that we have closed loop comms, because the Sol-Ark literally ran off by more than 20% within 2 days of getting a completely full charge! We had a Victron battery monitor starting the backup gen on voltage based settings, but when the Sol-Ark ran off that far the gen would start (because battery hit 50.7V), but the Sol-Ark was still showing 35%, and also grid power was on......... so the gen ran for something like 10 hours before they found out (they were gone when the gen started)..... Needless to say, the homeowner wasn't too pleased.

That whole job has been a disaster, as the EMP hardened 15K (that we swapped in after the initial install) had the internal CT sensors off of the wires, and therefore as soon as any power came from grid or went to grid it showed all kinds of crazy numbers! One day it pushed something like 25-30kw of battery power out to grid and sell was disabled.... the inverter simply had zero knowledge of grid side of things. I tried installing external CT's and that didn't work. Then I called Sol-Ark tech support, selected the option for when your are onsite, and ended up still getting voicemail. I left a voicemail and got a return call 4 hours later, which was after hours and I was home by then. They told me to call them again when I'm onsite, or schedule a call with them sometime that I can be onsite. I scheduled a call with them for a certain time, went on the job, found the internal CT's with no wires going through them, looked at another unit that I took along as a precaution, fixed the internal CT issue and was starting back up for testing when they finally called me...... an hour later than the scheduled time....... The job is about 50 minutes from the shop and I have made multiple trips to try to resolve Sol-Ark issues there. Kinda puts a sour taste in your mouth after a while. I am assuming the internal CT sensors got taken off the wires during the EMP "hardening" process at Sol-Ark. (I assume they do it "in-house" in Texas.) Some of the additional components (comparing to a non-EMP unit) were connected to the terminals were the "grid" wires, that should have been routed through the CT's, were connected to. Things do happen, people make mistakes.... but both CT's being off..... a bit frustrating! And if I could have talked to Sol-Ark on my first trip, they could have told me to check it that time. That cost our company probably an extra 3 or more hours of labor and driving time, plus fuel......

I totally get it that inverters will always have bugs that need to be ironed out and whatever, but when you start seeing random glitches that make no sense whatsoever, you start thinking that if you find a different, more dependable option, that it would probably be worth switching.....

To clarify on "glitches", I'm referring to things such as a double stack 15K system simply not charging, even though the batteries were dead, and I mean dead-dead.... like 50 volts or something like that. But as soon as we disabled Grid Peak Shave they started charging.......... ?????? And then a 12K in our showroom wouldn't sell any power out of the batteries, and this was after it had worked perfectly fine for a few weeks, and when we called tech support, they got us to change a few settings and nothing really worked until finally it was selling a measly 500watts, so tech support said to call them if we need anything else and finished up the call.... but TOU settings were set to sell 9000watts out of the batteries........ and then we remembered the other job so we disabled Grid Peak Shave and BOOM..... now the 12K started selling at the full 9000watt rate like it was supposed to. How is Grid Peak Shave effecting sell...???? And why would Grid Peak Shave keep charging from happening when there is literally ZERO load on grid and Peak Shave is set to 40,000 watts...???

I'm tired of the glitches. I'm tired of the SOC not working when they insist it does. I'm tired of tech support that is impossible to get ahold of.

Anyway.... enough of the rant. Just wanted to blow some steam and possibly give some other people a heads up of some of the things we have been dealing with. (And there has been more!)

We are still installing Sol-Ark inverters all the time.... mostly because there isn't a better alternative. There are plenty of other all-in-ones out there. But coming from working with brands like Schneider, Victron, Outback, Magnum etc. we see how much better a system works when you have the settings and functions available that you need, and so many of these other brands simply don't have the options! We like when we can install a system and walk away knowing that 99% of the time we will literally not hear of any issues for a few years after the install! I honestly can't say that with Sol-Ark inverters.....

 

[Cmiller]

Because Sol-Ark and every other major Inverter company have moved to close loop communications.
The battery manufactures also want their batteries connected Via Closed Loop.

I have question for you......

Do you simply not ever want to just come out and say that Sol-Ark has some issues that should be worked on??

Literally any comment you make about this issue defends them in some way shape or form.

It is flat out an established fact that their SOC tracking is trash! When you compare it to pretty well ANY other brand of shunt based SOC tracking device or inverter, they don't come anywhere remotely close!

The reason that I made this post to start with was in hopes that somehow we could get their attention. Why??? So that they can make their product be even better!!! Literally for the benefit of Sol-Ark (as well as us installers, of course), but Sol-Ark would benefit more than anyone else if they improved the issues that installers bring to their attention! But their response is always beat around the bush, or even flat out claim that the issue isn't an issue..... I just don't understand.

If you want to be the best, which they obviously do, in fact I think it is fair to say that they even claim to own this title already..... Then you should be open to improving when an issue gets brought to your attention!

One more note. You said the battery manufacturers want closed loop comms. Not all do.... Ark Battery (now Rubix) is a company that isn't necessarily all excited about closed loop comms. In the new Rubix batteries they have closed loop comms now, mostly because everyone thinks that is the way to go. But because of the history that one of the owners has in the solar installation industry and because of his extensive testing and R&D he is not necessarily all that excited with it. Closed loop comms brings a whole new can of worms in terms of firmware and programming issues. The BMS's have to be made to work with whatever inverter brands, then the inverter has to play nice with the BMS's, then if the inverter company makes changes there might end up being issues with the closed loop comms...... and guess who gets called..... I'm sure the inverter companies get calls as well, but I know for a fact that the battery companies do! Any time you have 2 different pieces of software trying to communicate there are a whole host of potential problems! And you have to keep in mind as well that there is NO STANDARD PROTOCOL for BMS closed loop comms! It's the dumbest thing, but I think it is that way because everyone is so focused on having proprietary software,as well as hardware, and then it just makes it harder for everyone! (Full disclosure, I don't work at or own Ark or Rubix battery. I do have close ties, and I have been involved here and there on some of the R&D and troubleshooting over the years.)

Anyway, @robby I do appreciate your interaction in this discussion. But I strongly feel that sometimes issues just need to be called out as issues and not beat around the bush to avoid calling it what is is!

If a company doesn't deliver what they promise in one area, chances are, down the road there will end up being many other areas where they fall short! Unfortunately this is simply how business tends to work! And if Sol-Ark doesn't get their act together on the 12K and 15K units, I hate to imagine the potential issues in the 30K and 60K...... Hate to say it, because we will very likely end up at some point using these bigger units somewhere, but facts are facts. If things don't work as they should, they need to be addressed and fixed!

 

[robby]

I have question for you......

Do you simply not ever want to just come out and say that Sol-Ark has some issues that should be worked on??

Literally any comment you make about this issue defends them in some way shape or form.

I have a suggestion for you.
Go look back at my Posts from 18 months ago when I was saying the same thing and expressing my frustration with the drifting. It was since explained to me by Sol-Arks head Engineer and I got what he was saying and it also matched what my external shunt and Individual BMS readings on my Packs are showing. Having an Accurate Shunt reading of the whole bank is not telling you anything about the SOC of the Individual Packs when Partial charges are happening on a daily basis.

This problem always comes up during the Winter periods and almost never in the summer because the batteries are typically fully charged in the Summer.
You have discovered nothing new. Myself and others have been discussing this issue for two Winters now and we know that Closed loop is the only good solution.

It is flat out an established fact that their SOC tracking is trash! When you compare it to pretty well ANY other brand of shunt based SOC tracking device or inverter, they don't come anywhere remotely close!

The reason that I made this post to start with was in hopes that somehow we could get their attention. Why??? So that they can make their product be even better!!! Literally for the benefit of Sol-Ark (as well as us installers, of course), but Sol-Ark would benefit more than anyone else if they improved the issues that installers bring to their attention! But their response is always beat around the bush, or even flat out claim that the issue isn't an issue..... I just don't understand.

Maybe because it's not an Issue for them as they stress that closed loop should be used.
They also have a listed of Recommended battery pack Manufactures that you should use.
If they removed the Open loop option or made a statement like Fortress Power. If you use our Inverter without closed loop or anything other than our recommended battery pack manufactures your Warranty is void!
Would a statement like that make you happy?

If you want to be the best, which they obviously do, in fact I think it is fair to say that they even claim to own this title already..... Then you should be open to improving when an issue gets brought to your attention!

One more note. You said the battery manufacturers want closed loop comms. Not all do.... Ark Battery (now Rubix) is a company that isn't necessarily all excited about closed loop comms. In the new Rubix batteries they have closed loop comms now, mostly because everyone thinks that is the way to go. But because of the history that one of the owners has in the solar installation industry and because of his extensive testing and R&D he is not necessarily all that excited with it. Closed loop comms brings a whole new can of worms in terms of firmware and programming issues. The BMS's have to be made to work with whatever inverter brands, then the inverter has to play nice with the BMS's, then if the inverter company makes changes there might end up being issues with the closed loop comms...... and guess who gets called..... I'm sure the inverter companies get calls as well, but I know for a fact that the battery companies do! Any time you have 2 different pieces of software trying to communicate there are a whole host of potential problems! And you have to keep in mind as well that there is NO STANDARD PROTOCOL for BMS closed loop comms! It's the dumbest thing, but I think it is that way because everyone is so focused on having proprietary software,as well as hardware, and then it just makes it harder for everyone! (Full disclosure, I don't work at or own Ark or Rubix battery. I do have close ties, and I have been involved here and there on some of the R&D and troubleshooting over the years.)

Yes but Ark Battery/Rubix is just one Manufacturer. Almost all the rest including even many of the non branded, Chinese versions are pushing closed loop.
I don't even understand Rubix's position on the matter other than for cost cutting. Yes the support and updates cost money but if you want to be competitive you have to offer what the other companies offer.
One of the other Reasons why closed loops Comm is moving so fast is that the new UL-9540 2020 certifications require that Batteries and Inverters to be matched together for certification. So most companies started moving in that direction right after 2020. The revision for 2023 does ease up on this but it will probably not be incorporated for several more years and might change back again.

Anyway, @robby I do appreciate your interaction in this discussion. But I strongly feel that sometimes issues just need to be called out as issues and not beat around the bush to avoid calling it what is is!

I do call them out and I did call them out on this one, but after seeing the full blown push to closed loop it just did not make sense to harp on something that is not relevant to 95% of newer installations.

If a company doesn't deliver what they promise in one area, chances are, down the road there will end up being many other areas where they fall short! Unfortunately this is simply how business tends to work! And if Sol-Ark doesn't get their act together on the 12K and 15K units, I hate to imagine the potential issues in the 30K and 60K...... Hate to say it, because we will very likely end up at some point using these bigger units somewhere, but facts are facts. If things don't work as they should, they need to be addressed and fixed!

30K and 60K are already being installed commercial buildings.
So far my Contact at Sol-Ark says that no problems are showing up.

 

[Cmiller]

I have a suggestion for you.
Go look back at my Posts from 18 months ago when I was saying the same thing and expressing my frustration with the drifting. It was since explained to me by Sol-Arks head Engineer and I got what he was saying and it also matched what my external shunt and Individual BMS readings on my Packs are showing. Having an Accurate Shunt reading of the whole bank is not telling you anything about the SOC of the Individual Packs when Partial charges are happening on a daily basis.

Good quality batteries with good balancers shouldn't have too much issue with variation between individual units. Therefore having an inverter/ battery monitor/ system or however you want to describe it, that works right with open loop, and that can relatively accurately track SOC% works very well!

For instance this battery bank:

16 units. They haven't gotten completely fully charged for probably a full month now! The bottom 2 are at 66% and 50%. The rest are between 39-43%. You keep saying you need closed loop comms for imbalances........ We honestly have ZERO issues caused by imbalances between units! Not just on this system (in our shop), but also many many many other customer's systems! Obviously here and there we do see a little bit of a spread, as you can see on this specific system. (And by the way this system has the worst spread that I have seen, with those bottom 2 batteries, but these units were actually run completely flat dead because the balancers were by accident hooked in on battery side of the main breaker, so drained them completely during shipping, and while sitting waiting to be installed. So we installed them at our own shop to avoid issues for a customer.) Our gen auto starts and stops on voltage, and we simply don't do a thing with the system! We have yet to have a single issue come up because of imbalanced SOC between units! Whenever they get completely full, they get "balanced out" again. The Schneider Battery monitor does a pretty good job of tracking the SOC, but the actual screens on the batteries have currently drifted ~15% or so, judging by what the SOC is when the gen starts up.

So tell me how this system could function any better using closed loop comms??

This problem always comes up during the Winter periods and almost never in the summer because the batteries are typically fully charged in the Summer.
You have discovered nothing new. Myself and others have been discussing this issue for two Winters now and we know that Closed loop is the only good solution.

But why don't we have any issues whatsoever on our open loop Schneider and Victron systems, even during the winter...??? Sure there may be a slight, slow "calculated" SOC drift over a few weeks time, but not in a few days!

Maybe because it's not an Issue for them as they stress that closed loop should be used.
They also have a listed of Recommended battery pack Manufactures that you should use.

If they removed the Open loop option or made a statement like Fortress Power. If you use our Inverter without closed loop or anything other than our recommended battery pack manufactures your Warranty is void!
Would a statement like that make you happy?

No, it's actually pretty simple. I would like one of 2 things.

• Either don't say you can accurately track SOC, and if a customer has an issue with it, just admit that it doesn't work very well.
• Or, they could listen to the issue, and fix the issue. It honestly can't be that hard to improve, just judging by all the other brands that work better!

Yes but Ark Battery/Rubix is just one Manufacturer. Almost all the rest including even many of the non branded, Chinese versions are pushing closed loop.
I don't even understand Rubix's position on the matter other than for cost cutting. Yes the support and updates cost money but if you want to be competitive you have to offer what the other companies offer.

You are correct that you have to offer what others offer! Ironically enough the Rubix GigaStack batteries, which have the same cells as the Ark but now have a smart BMS with closed loop comms, are a few hundred dollars cheaper. So no, it isn't really for cost cutting.

Sometimes when you have experience with having installed literally hundreds of systems, you see real world performance things that a corporate company with little (or no) in-the-field experience doesn't see.

One of the other Reasons why closed loops Comm is moving so fast is that the new UL-9540 2020 certifications require that Batteries and Inverters to be matched together for certification. So most companies started moving in that direction right after 2020. The revision for 2023 does ease up on this but it will probably not be incorporated for several more years and might change back again.

I may be wrong here, but I believe the new UL-9540 would basically be that the complete system has to be UL tested/listed as a complete system. For example: Ark batteries with Sol-Ark 15K, or Eg4 batteries with Schneider XW Pro inverter, Mppt60, AGS, Batt Monitor, etc. In other words all the components of the complete system tested together. I don't believe closed loop comms is a requirement of it. Again, I could be wrong.... I can't say 100% for sure.

30K and 60K are already being installed commercial buildings.

Yep, and we have already quoted a 60K. And I know our local dealer had one that they were testing and then sold to someone. I know they are out there. But from what I saw, it seemed like the menu layouts were pretty well identical, to the 12K and 15K, which while I realize that just makes sense to keep it similar across the board. But, that also tells me the backend programming is pretty well identical, other than the "size" of the voltages being worked with. As far as batteries on those, that's a whole other animal when you get into high voltage batteries, so I'm not really referring to that specifically as I have no experience with high voltage batteries! But things like having random glitches and also the lack of a proper gen auto start menu are the type of things that I don't like.

The auto start thing already blows my mind. For all practical reasons, if you have an auto start relay, you need a proper menu with start and stop parameters etc. And also the fact that charging with a gen during grid outage will be limited to the Time Of Use setpoint simply doesn't make sense...... So things like that are what I am concerned about on the bigger units. A residential customer who enjoys "playing around" with his system may well be fine with manually adjusting setting when there is a grid outage. But in a commercial application, as the 30K and 60k will undoubtedly be used for, you simply must be able to set it up in a way that is foolproof!

So far my Contact at Sol-Ark says that no problems are showing up.

So you are pretty sure that your contact at Sol-Ark would definitely let you know if there were issues...?? And you are confident that any issues would also be viewed by Sol-Ark as issues and not just skirted around...?? And you are also, of course, sure that there wouldn't be any "bugs that come up down the road, or specific scenarios that Sol-Ark would not have been able to foresee and test out..???

Just out of curiosity.... how many solar/inverter/battery systems have you personally worked on?

 

[robby]

Ark battery is not a Sol-Ark Battery Partner and it is not listed as working in closed loop coms with Sol-Ark Inverters. They state the have a "Working relationship" with them, whatever that means.
Maybe they are still doing development to get the closed loop system working.

Other Batteries like Fortress Power and EG4 Will Work in Closed Loop but they are not listed.
Fortress use to be listed but I guess they got booted after the Envy Inverter came out.



Your drift of 15% is way higher than I would tolerate. The most I have ever let mine drift is 10%.

I am not a Solar Installer, I am Electronic Engineer & CE.
The only Solar installation I have done is my own.
I have worked on fixing issues with a few other installations but that is about it.

As for issues with the 30K or 60K I have no idea why they would lie and since most problems come from the Firmware and as you said they are using the same firmware, I would expect that it works properly just like the 8/12/15K models.

 

[Cmiller]

Ark battery is not a Sol-Ark Battery Partner and it is not listed as working in closed loop coms with Sol-Ark Inverters. They state the have a "Working relationship" with them, whatever that means.
Maybe they are still doing development to get the closed loop system working.

Ark batteries have no smart BMS, and no comms ports period. As such, they won't ever have closed loop comms..... I believe I stated that before. Extremely robust batteries, they simply work! We can install them and walk away knowing they will work. The working relationship means that there have been meetings between the owner of Ark and Sol-Ark, that Ark batteries can be used with a Sol-Ark inverter, etc. Nothing to do with closed loop comms. And they do work perfectly fine with Sol-Ark inverters as long as you don't need % on the Sol-Ark itself.
Rubix GigaStack is the "new" Ark, same cells and quality, etc., but with smart BMS and closed loop comms.... Also more finicky due to the smart BMS..... exactly why Ark were originally designed with a "non" smart BMS. But now with how everyone pushes for closed loop, you either have to stay "with it" or you will lose out. Hence the smart BMS and closed loop comms.

My info on the Ark and Rubix scenario is, by the way, not word of mouth. It is from my firsthand connections to the company, and actually working side-by-side quite a bit....

Your drift of 15% is way higher than I would tolerate. The most I have ever let mine drift is 10%.

To be honest I highly doubt that the actual state of charge is drifted 15%. I suspect simply a drift of the "screen" on the battery, as the batteries had not been fully charged for a number of weeks. I could be wrong on that, but the nature of voltage difference between batteries causing charge to flow between units tends to keep from having too much drift. My own batteries at home (experimental units with smart BMS's, but running open loop) have a variation as well, and the one unit showed ~70-75% even after the whole bank got charged completely full, all the way up to around 56V last weekend. This is simply a drift of what the smart BMS believes the SOC is at. It would probably re-calibrate to 100% if I would take the charge voltage up to ~57 volts.

But even if there is 15% difference, what are we hurting? We see no adverse, strange behavior, no odd battery bank voltage drop etc.....
Let's say we charge then discharge 30% every day for 2 weeks, so that would be a 30% DOD every day (not actual numbers, just hypothetical) what is the difference (or the drawback) between the units that cycle between 15-45% vs the units that cycle between 30-60%? At the end of the day the each still did a 30% DOD...

Now if you would have one unit cycling at only a 15% DOD while the others did a 30% DOD, that is a whole other story. But we generally don't see a variation like that on LFP batteries that are of decent quality components, regardless of the brand. And also, closed loop comms will not adjust charging amps between units, to my knowledge, so it really won't help anything in terms of imbalance, other than shutting down discharge if one unit shows 0% (or whatever % you would set it) while the others would show, say 30%. But of course, as you can see from my personal bank with one BMS off by ~25%, I would have shutdown issues before the bank is actually low if I would be using closed loop! I really truly don't think it is possible to have a spread in actual internal SOC more than~10% or so, between LFP batteries with the same cells internally! If you look at voltage curves on charge and discharge, the way the voltage drops off in the bottom 25%, and they way it rises in the top 15-20%, I think it keeps them relatively well "balanced" out between units.... That middle 50% may be able to spread more, but you will hardly ever sit in the middle 50% for any extended period of time!

I am not a Solar Installer, I am Electronic Engineer & CE.
The only Solar installation I have done is my own.
I have worked on fixing issues with a few other installations but that is about it.

Speaking for myself, I am a Solar Installer and service technician with 10+ years of experience in the field. I have worked on hundreds, if not thousands of systems. Probably 95% of those were off grid, the other 5% grid tied or hybrid, with the last 2-3 years being more like 10-15% grid tied or hybrid. Probably 75% of the off grid and hybrid systems that I have worked on have some kind of SOC tracking device, all pretty much exactly what Sol-Ark has integrated specifically for batteries that do not have closed loop comms. Shunt based, often using a 500A/50mv shunt, tracking down to a fraction of an amp. Sol-Ark has this built-in so their inverter can be used with any 48V battery..... I believe they would say so themselves!

The Sol-Ark algorithm is simply inferior! I speak from experience....... I speak from all the other brands that I have seen work absolutely fantastic and both lead acid and/or LFP batteries, or even with salt-water batteries for that matter. These other units work with both open loop and closed loop LFP batteries..... In fact oftentimes in off grid installs we won't even bother using closed loop comms even when it is available, because open loop works so well, and maybe it's an existing Schneider system (or whatever brand) with existing shunt based SOC that works. So we adjust the settings for the new LFP batteries and walk away knowing it will work. But not so with Sol-Ark.....

I would think if you are an Electrical Engineer you would understand that sometimes the hardware is not the issue, but rather the software. And sometimes the end user/ installer sees the real world side of what works and what doesn't!

I find it very strange that you (I mean you personally) would continue to pose this as not an issue, when I have given examples of it not working, as well as the fact that I am also speaking from a number of years' experience on the subject (that you don't have)...?

As for issues with the 30K or 60K I have no idea why they would lie and since most problems come from the Firmware and as you said they are using the same firmware, I would expect that it works properly just like the 8/12/15K models.

You would expect that it works properly just like the 8/12/15K models....... perhaps you are not understanding that there are actually issues with those units...?

As far as why they would lie.... sometimes it is not so much the things that are said, as the things that are not said. Why would they want to tell you about an issue that has come up? It is simply common sense to expect that they won't be telling you if they had an issue come up! I would assume they would try to fix any issues to avoid having customers telling other people that their units have issues! But my concern is the fact that when I as an installer brought up issues, they did not listen and address the issues. So, what if I, as an installer, bring up an issue on the 30K or 60K? Why would I expect them to listen to me when they have not listened so far?

I will give an example:
This is an actual install, and actual problem...
3x Sol-Ark 15Ks, set up for 120/208V 3 phase, set up in Limited to Home mode (using CT's) on 2- 45kw gensets that can run in parallel for a total of 90kw. The Sol-Ark 600A CT's are in place and in use (45kw is approx 125A at 3ph 208V, 90kw is approx 150A at 3ph 208V), but any time that more than 40kw is drawn through those CT's I lose all monitoring of power through the CT's! There was one day where the Sol-Ark's said the power drawing through the CT's was ~40kw when it was actually 80kw! It pretty much flatlines at 40kw, once you are there or higher!

I asked tech support about it and they asked someone further up and came back saying that the actual circuitry in the Sol-Ark is not capable of monitoring over 40kw using the CT's..... I didn't get any technical details, just that. So I asked if I could use a different CT ratio, 6000:1 instead of 2000:1, to theoretically be able to monitor 3x as much, or 120kw. The response was that Sol-Ark does not recommend using other CT's with other ratios..... now what I am I supposed to do with that?

In an email with someone further up at Sol-Ark, I noted this issue and I got no response on it. This is an actual, real world situation where eventually I will need to be able to monitor higher than 40kw in order for the Sol-Ark system to work properly! At this point I have no idea what I will do once they need the additional power over 40kw....

I also asked (in that same email) whether the 30K and 60K will have this same issue or not..... I got no response on that either. And seeing how much is the same or similar on the bigger units vs the 15K, I tend to think that the issue may well be present in the bigger units also.....

Do you think I would be excited to install a 30K or a 60K? If I would want to do peak shave using limited to home and CT's I wouldn't even know how many kw I can Peak Shave at.....

Sol-Ark has phenomenal tech support for the average homeowner who wants to have the system explained and wants to know how it works, etc.! But when it comes to technical backend things that are above the regular tech support level, it seems so far that they are very poor at listening and/or providing solutions! As of the last few months, I can't even expect to be able to get ahold of Sol-Ark tech support when one of our service guys, or myself are onsite to diagnose an issue. Not even when we select the onsite phone que option! This results in multiple truck rolls to get an issue resolved. That costs us money, and causes frustration for the homeowner!

 

[robby]

I would think if you are an Electrical Engineer you would understand that sometimes the hardware is not the issue, but rather the software. And sometimes the end user/ installer sees the real world side of what works and what doesn't!

I find it very strange that you (I mean you personally) would continue to pose this as not an issue, when I have given examples of it not working, as well as the fact that I am also speaking from a number of years' experience on the subject (that you don't have)...?

The replies have gotten so long that I cannot even respond to all of it.
I think your ignoring the fact that I stated that I was one of, if not the first person on here to bring up the Subject of the SOC drifting with the Inverter and complaining about it.

I am simply stating that all of the companies in both the Inverter and Battery business seem to have moved on from depending on the Inverter to calculate SOC with LFP batteries.
Long before Sol-Ark said anything to me on going Open Loop it was Fortress Power that was pushing me to go back to closed loop. After all it is not the Inverter that is going to get damaged if some kind of low voltage situation arises, so there is no warranty expenses for them to worry about.

BTW your scenario of a battery dropping to the cut off point and just dropping out, may be fine for larger installations, but when I only had 10KWh of batteries it was a warranty provision by Fortress Power that I have Closed Loop. I am sure that you know that if one pack drops out the other one can be damaged by a surge and blow the Class T Fuse or damage a BMS if it is Mosfet based.
The Closed Loop Comms with the Fortress Batteries is constantly updating the Total Amount of Amps available to the Inverter. If one goes down the Max Amp setting in the Sol-Ark will drop by that amount.
Therefore the Inverter will not try to pull anymore power than what the online packs can deliver.
Here is a snippet of Fortress Powers Guidelines that I had to follow.
Anything below three packs with the 12K required Closed Loop Comms.

 

[Cmiller]

The replies have gotten so long that I cannot even respond to all of it.

My apologies! I tend to get long-winded.

There are a few facts that remain-
-The Sol-Ark does not accurately track SOC despite the company insisting that it does!
-Sol-Ark as a company is not willing to listen to an installer and try to improve.
-Sol-Ark has failed time and time again to give me satisfactory fixes to real issues that my customers see, and as such, these issues are still out in the field.
-If the 12k and 15k units have issues, then the 30k and 60k units will likely have issues as well. Especially seeing as they seem to have the same "programming backend".

When I told Sol-Ark reps that because of some of these issues I'm open to a different brand that has solutions, they literally said "I understand".

Now, as you have seen and commented on as well, Midnite has brought an AIO unit to market. I expect that we will very likely switch to Midnite, because I know 100% for a fact that Midnite products can accurately track SOC, that they have proper gen start menus, that they know how to create inverters will real surge capability, and that they provide fixes for problems that may come up, and I can get ahold of someone any time I might run into an issue.... I mean what more could we want.... Even when someone suggests a function that would be very handy, if it's something practical, they literally bring it to the engineers and see if they can incorporate it! When I brought up a proper gen start menu to Sol-Ark they literally said despite many people asking for it, they won't add it in any current models.....?? Say what....???

 

[b.shaw]

Sol-Ark's SOC tracking algorithm runs off and jumps around! And so far I have gotten no satisfactory response from them on any solution!

The scenario is that we have quite a few Sol-Ark's out there with LifePo4 batteries that have no closed loop comms, but with shunt based SOC screen built-into the battery. (Ark battery brand) The Sol-Ark inverters are terrible on tracking the SOC!!! We see them often being off by 50% or more, and the SOC will jump as much as 50-70% at the drop of a hat!

I have worked with battery monitors from Schneider, Magnum, Midnite, Outback, Tri-metric, Victron, etc., etc......... And Sol-Ark is the worst, by far!

It is extremely disappointing that they are not better, when their spec sheet even says they have a shunt "for Accurate % SOC".

Where we really run into issues is on the (quite a few actually) jobs that we are using Time-Of-Use settings to do Limited to Home with no grid sell. When you go SOC based, there are issues where the Sol-Ark says SOC is 50% and the batteries are actually at 15%.... or 5%.... or even completely dead.... I'm talking 49-50V on 16s LFP batteries. Then when the voltage hits the battery empty volts setting, (49V is where we generally have it set) the SOC snaps to 0%.

If we are using the gen start relay this obviously creates issues if we want to start the gen at say, 15% when grid is down, but the Sol-Ark thinks SOC is still at 50% until the batteries are flat dead! There is a huge risk of the system shutting down or even the BMS's shutting down in this scenario. We have one customer who goes to Florida over winter, and he wants to be able to not worry about the system while he is gone, and of course with this issue you can't really actually depend on the backup generator to for sure start in time.

Switching to voltage based is not a viable option, as the Sol-Ark uses the Time-Of-Use setpoint to limit gen charging as well......

So for reference: Using voltage based settings, TOU set to 52V, gen start set to 50.7V (roughly 15%). Now when grid happens to be down for a few days and the battery volts hits 50.7V and we begin to charge at 175A (using Kohler 14KW standby gen), how long until our 300-500AH battery bank hits 52V????? 30 minutes..??? How many times would the gen start in 24hrs? Many times!

Sol-Ark says "use a battery with closed loop comm". Why? Why do they say they have SOC monitoring, when in fact, it doesn't work? Why do we need to come up with work-arounds to overcome the shortcomings of an inverter not having what it is advertised to have?

I emailed them about this issue as well as some others and they at first said they need a few days to look over the issues. Then I got no response and finally after 4 weeks I emailed them and told them I need answers! Now they emailed me back and here is the response:

View attachment 181371

Here is my original email:
View attachment 181369
View attachment 181370

The spec sheet for the 15K says they have a shunt "for Accurate % SOC". I would not say that showing 50% when batteries are at 25% is anywhere near to "accurate"! Neither is it an acceptable margin of error. That is what we saw yesterday on our one job. (Actually the customer sent me these pics wondering if this is right or how it should be.... How do I respond to that...??)

View attachment 181374
View attachment 181375

This battery's screen is actually shunt based, and these screens have always been very accurate! Obviously any SOC monitoring device can, and will, sometimes run off! But in the grand scope of things, these have actually done better than any battery monitor from any inverter manufacturer that I have ever worked with. So as you can see, the Sol-Ark isn't even remotely close.....

As far as the jumping around of the SOC on the Sol-Ark goes, here are some screenshots showing that:

View attachment 181376
View attachment 181377
View attachment 181378
View attachment 181379
View attachment 181380
View attachment 181382
View attachment 181390
View attachment 181391
View attachment 181392

Some of these screenshots are from PowerView, others are from a Solar Assistant that is on our one job, so all of that data would have been directly collected in realtime from the 3x Sol-Arks that are on that job.

I really wish this post would somehow get the attention of Sol-Ark, and they would work on this. But at this point my faith in that is pretty small...

The Sol-Ark inverter can't be beat in terms of simplicity and also they just have an absolutely great all-in-one platform! That is why we use a ton of these units! And compared to other brands they rule in areas like stringing solar panels (26A pr mppt, why doesn't anyone else do that????), 200A passthrough is great and not many others have that, the menu is better than pretty much any other all-in-one (although it is way behind when compared to non all-in-one setups like Schneider, Victron, etc., etc., etc.), built-in battery breaker, we really like their battery terminals as well, and even their solar wire connectors are hard to beat!

But if I constantly have customers calling with issues that have to do with a problem with the programming of the inverter, I very quickly start feeling like it would be worth it to revert back to a non all-in-one system. A system that we can install and know pretty much with 100% certainty that we can walk away from it, and it'll just work! A system where we can tell the customer "your generator will start before the batteries are dead". A system where we can say, just look at this screen to see what % your battery charge is at.

Sadly, this issue is literally only a software issue! All it would take is some programming, and it could be fixed! But the response is that there won't be a change.....

P.S. For a backdrop, I have been in the solar industry for over 10 years, I have personally installed probably 400+ battery setups, and we as a company have installed 100+ Sol-Arks. So I'm not at all new to this stuff. I have seen things that work, and I have seen things that don't work. I prefer what works! ??️??

Hi,

I didn't catch your name, but mine is Bill.

TLDR: EG4 SOC calculations suck and there is going to be no real fix.

I installed my system a little over a year ago, Dual Sol-Ark 12K, 18KW PV, 62KWh EG4 Lifepower4. My goal is to not use grid power, but we have it available. I have been chasing this SOC problem since the winter solstice approached and we started not getting enough PV to fully charge the batteries. When we have excess PV power the system charges fully and everybody involved gets back in sync @100%. Once we no longer fully charge, the Sol-Arks start to drift from the REAL SOC (the EG4's SOC). The more days that go by, the farther away it drifts. Eventually it gets to the point where the Sol-Arks think there's 20% left when the batteries actually have 50% and the Sol-Arks shut down, plunging us into darkness when we still have half of our capacity.

I've been 'round and 'round with Sol-Ark, EG4 and Signature Solar. The bottom line is there is no solution to this problem and no intent to treat it as a problem. I have suspicions as to why this is, but I don't have enough inside information to be sure where the problem lies, (the 'lack of desire to fix the problem' problem) so I'm a bit reluctant to speculate.

I did get a suggested 'fix' from EG4 - fully discharge the batteries then fully recharge 14 times as quickly as we can, once/day or faster if possible. Obviously that 'fix' is a non-fix and patently absurd. How do I drain and recharge 62KWh 14 times in rapid succession? For a software bug workaround? No - that is not a fix, just a deflection.

So my fix is to set the battery's shut off point at 5% instead of 20% (could set it to 0%) and completely ignore the Sol-Ark's SOC. It is wrong anyways, so ignoring the bad data is valid. If my batteries ever get drained that far the EG4 BMS handles it.

I ended up doing similar on the charge side, essentially disabling the Sol-Ark's charge control and letting the battery BMS control the charge. If Sol-Ark cannot correctly calculate the SOC why would it correctly handle charge parameters & rates properly? Sol-Ark BMS is redundant anyways, EG4 has a much better handle on what the battery needs than Sol-Ark (obviously).


Probably not much help, but that's my experience.

Best,

Bill

 

[Cmiller]

Hi,

I didn't catch your name, but mine is Bill.

TLDR: EG4 SOC calculations suck and there is going to be no real fix.

I installed my system a little over a year ago, Dual Sol-Ark 12K, 18KW PV, 62KWh EG4 Lifepower4. My goal is to not use grid power, but we have it available. I have been chasing this SOC problem since the winter solstice approached and we started not getting enough PV to fully charge the batteries. When we have excess PV power the system charges fully and everybody involved gets back in sync @100%. Once we no longer fully charge, the Sol-Arks start to drift from the REAL SOC (the EG4's SOC). The more days that go by, the farther away it drifts. Eventually it gets to the point where the Sol-Arks think there's 20% left when the batteries actually have 50% and the Sol-Arks shut down, plunging us into darkness when we still have half of our capacity.

I've been 'round and 'round with Sol-Ark, EG4 and Signature Solar. The bottom line is there is no solution to this problem and no intent to treat it as a problem. I have suspicions as to why this is, but I don't have enough inside information to be sure where the problem lies, (the 'lack of desire to fix the problem' problem) so I'm a bit reluctant to speculate.

I did get a suggested 'fix' from EG4 - fully discharge the batteries then fully recharge 14 times as quickly as we can, once/day or faster if possible. Obviously that 'fix' is a non-fix and patently absurd. How do I drain and recharge 62KWh 14 times in rapid succession? For a software bug workaround? No - that is not a fix, just a deflection.

So my fix is to set the battery's shut off point at 5% instead of 20% (could set it to 0%) and completely ignore the Sol-Ark's SOC. It is wrong anyways, so ignoring the bad data is valid. If my batteries ever get drained that far the EG4 BMS handles it.

I ended up doing similar on the charge side, essentially disabling the Sol-Ark's charge control and letting the battery BMS control the charge. If Sol-Ark cannot correctly calculate the SOC why would it correctly handle charge parameters & rates properly? Sol-Ark BMS is redundant anyways, EG4 has a much better handle on what the battery needs than Sol-Ark (obviously).


Probably not much help, but that's my experience.

Best,

Bill

Thanks for the response Bill! (I am Conrad, by the way.)

I think there are a lot of people dealing with this issue and this is exactly why I posted this on here! To hopefully get attention, and have other people verify that they have the same issue!

SOC, understandably, will drift some in the winter when the batteries don't get full for extended periods of time! That is inevitable. However, when compared to other SOC tracking devices, the Sol-Ark's are in a whole other category! literally within 36 hours or so of a full charge they can be off by 15% or more! I tend to think that some of the issue is that they do not measure a small enough amount of current, and therefore especially when sitting at an "at-rest" state, or not really drawing power out of the batteries or charging, there are small amounts of current flowing but not getting measured, and that quickly adds up! I could be entirely wrong on that specific suspicion, however, what I'm not wrong on is the fact that other brands track SOC waaaayyyy better using a shunt, just like Sol-Ark does! Therefore it is obviously simply a programming issue.

I do think that you are correct in thinking that there is a lack of wanting to improve it! I find it sad that they handle it this way!

 

[LydMekk]

This is why I no longer trust ANY SOC calculations.
Either from inverters or batteries.
The only difference between BMS comms and voltage is that the first put in the necessary voltage data on the parameters in the inverter automatically.
With voltage you have to think and register the values manually.
THERE ARE NO OTHER DIFFERENCE.

What every owner should do is print out a piece of paper with the cell voltages list
which corresponds to what level of charge and hang it on the wall beside their inverter.
Stick to that as a SOC and look at each of the cell voltages from the batteries.
And for this the internal screen on each battery is sufficient.

Of my 6 different BMSs NONE show the same SOC. NONE.
I've given up trusting a BMS screen or readout when it comes to SOC in percentage.

 

[Ampster]

The reason I used an Orion JR2 BMS is twofold. It is contactor based and it has more accurate SOC and voltage measurements. My cells are EVE LF280 in a 3P16S configuration. The Orion JR2 allows you to set the Victron protocol and then follow the instructions in the SolArk battery interface download manual