Sol-Ark 15K + SOK batteries = Weird SOC issue

[Watts Happening]

This, regardless if you're using open or closed loop.

According to my SA data the grids been up and down a few times today...


Exactly.... The whole purpose of having battery with grid backup goes out the window.

I can completely see your viewpoint, however on the flip side of the coin there are those of us that are city dwellers with exceptionally reliable power grids. I’ve had a single power outage I can remember in the last 5 years that lasted for all of 30 minutes due to an apparent car crash.

For me, the additional 10% of usable battery capacity on a daily basis far outweighs the remote chance of grid failure. In that unlikely event I have multiple generators, fuel sources and generally just an abundance of ways to get power back into the batteries.

My goal is to rely on the grid as little as possible, and that additional capacity helps accomplish that goal. It’s actually rather hard to be 100% solar powered where I live due to winter and us using mini splits for all of our heating. Summer we have quite the excess of power, winter is another story and where this capacity can make quite the difference.

 

[G00SE]

I think I’d run a bit higher on the charge for a few days/cycles to let the packs balance as @42OhmsPA indicted and then maybe test 10-15% and see how the system responds? 5% is awfully low.
Would be an easy way to rule out or in that as the culprit. And if it’s not, at least your batteries will be happy

 

[Watts Happening]

I think I’d run a bit higher on the charge for a few days/cycles to let the packs balance as @42OhmsPA indicted and then maybe test 10-15% and see how the system responds? 5% is awfully low.
Would be an easy way to rule out or in that as the culprit. And if it’s not, at least your batteries will be happy

That’s my plan, I don’t have any intention to dip down to 5%. I think 10% is a very reasonable number based on our loads and usage

 

[#40Fan]

If you know exactly where the BMS reports 0% SOC, you might be able to run it down to 0% without any issues.

 

[Cmiller]

..... Try throwing 300A at any system at 99% SOC - you would instantly hit OVP, guaranteed.

You sure about that? Has anyone tested that? And I guess I should also be asking, at what charge voltage are you talking?

Because from what I have seen at home with my AC coupled off-grid system, it is amazing how much current can be injected for a few minutes even when the batteries are basically completely full! Now I have never actually experimented with something like 300A, and also my battery bank is 600A 48V, so I have a decent amount of capacity there to help absorb current....

I tend to think that as long as you are not at a voltage higher than ~56.6-56.8 and your battery bank is 300AH or larger you should be able to pump 300A into it for short periods of time without issues.... I guess that would also depend on BMS amp rating. If you go over what the BMS's can take they definitely will shut off! But then that really wouldn't be because of how full they are, but rather because of the amperage.

Do you know of any videos out there where someone has experimented with this? We will soon be getting our lab set up at Rubix with all kinds of load banks and charging options, so maybe we can do an actual test on this! Seems like a fun thing to test out!

 

[HighTechLab]

You sure about that? Has anyone tested that? And I guess I should also be asking, at what charge voltage are you talking?

Because from what I have seen at home with my AC coupled off-grid system, it is amazing how much current can be injected for a few minutes even when the batteries are basically completely full! Now I have never actually experimented with something like 300A, and also my battery bank is 600A 48V, so I have a decent amount of capacity there to help absorb current....

I tend to think that as long as you are not at a voltage higher than ~56.6-56.8 and your battery bank is 300AH or larger you should be able to pump 300A into it for short periods of time without issues.... I guess that would also depend on BMS amp rating. If you go over what the BMS's can take they definitely will shut off! But then that really wouldn't be because of how full they are, but rather because of the amperage.

Do you know of any videos out there where someone has experimented with this? We will soon be getting our lab set up at Rubix with all kinds of load banks and charging options, so maybe we can do an actual test on this! Seems like a fun thing to test out!

The batteries start limiting current when cell voltage is above ~3.55v. Between 3.55 and 3.65 is only a few tenths of an amp-hour. Even with 6 batteries, 50A per battery would pass OVP in seconds.

 

[Cmiller]

The batteries start limiting current when cell voltage is above ~3.55v.

I assume you are referring to the BMS limiting the current internally. But that would depend on the brand of BMS. Many brands do not limit charge amps. With a good active balancing system there is no need to limit current through the BMS.

Between 3.55 and 3.65 is only a few tenths of an amp-hour. Even with 6 batteries, 50A per battery would pass OVP in seconds.

I find that a little hard to believe, but to be fair, I have not specifically done any "playing around" with that scenario. I think I need to try it!

 

[marionw]

With respect to the original post of not being able to draw the batteries down to 10% SOC.
If you look at the "Parameter Settings" tab in the SOKTool software the "SOC Low Alarm(%)" is set to 20%. I assume when the BMS reports SOC Low Alarm the inverter will stop drawing from the batteries. This value would have to be decreased.

 

[HighTechLab]

assume you are referring to the BMS limiting the current internally. But that would depend on the brand of BMS.

This thread is about the SOK 48v100ah batteries. They limit the current by instructing the inverter to slow down via CANbus communication.

I also have done the testing we are discussing. I am the guy that did most of the design of these packs after all…and wrote the whole manual from scratch that accompanies them.

 

[Cmiller]

..... Try throwing 300A at any system at 99% SOC - you would instantly hit OVP, guaranteed.

This wouldn't sound to me like a reference to just SOK, being as you said "any system".

No disrespect here regarding SOK batteries and your involvement! I was simply stating that I'm not sure that this is how it would work on "any system". (Again, your words.)

And also, just to clarify, my personal system that I mentioned is not SOK batteries! And I was not referencing closed loop comms scenarios! Hopefully I didn't confuse anyone on that!

My apologies for derailing the thread. My comment really had nothing to do with the OPs question. In fact I didn't bother responding to the question, because you explained perfectly to OP what was happening! (The SOK batteries are simply telling the inverter to stop discharging at 20%.)

 

[networksguy]

Basically I can't get my Sol-Ark to discharge the batteries below ~19-20% unless I disable closed loop communication.

My Sol-Ark 15k with Kilovault batteries, in closed loop, behaves the same. It will not draw from the batteries when SOC is below 19% and the grid is available. Like you, I too would perfer to get more daily use of the batteries and I'm less concerned with power outages.

 

[Watts Happening]

My Sol-Ark 15k with Kilovault batteries, in closed loop, behaves the same. It will not draw from the batteries when SOC is below 19% and the grid is avaiable. Like you, I too would perfer to get more daily use of the batteries and I'm less concerned with power outages.

I’ve now been into the programming of the batteries but unfortunately not making any progress. From what I can see they are all set to 5% SOC alarm, which was how they were when I connected. This has me back to the drawing board as to how/why it’s happening. Hoping to hear back from a couple private messages I sent to Dexter.

 

[marionw]

For @networksguy . You will need the software and appropriate cable that allows you to monitor your batteries with a computer.
Most BMS's have an SOC Low alarm setting and it probably is set at 20%. In closed loop, if this alarm is raised and sent to the Inverter I would assume the Inverter would stop drawing power from the battery. Changing it may not solve the issue because the BMS also uses other logic to control the state of the "DISCHARGE" MOSFETS. The BMS may use the Pack Under-voltage Protection as well as Cell Under-voltage Protection setpoints to turn off the "DISCHARGE" MOSFETS which prevent further discharge of the battery.

Keep in mind that modifying the BMS setpoints may void your warranty.

 

[Watts Happening]

Anyone have any other ideas? Haven’t heard back from @HighTechLab but I assume he’s a busy guy. Hoping to get this sorted as it’s pretty much the only ““problem”” I’m having, want to do it before expanding the bank.

 

[ksmithaz1]

I've had some similar issues with my batteries. I think if I tell my inverter to take the batteries to 1 effing percent, then they should run until it gets to 1 effing percent. I think if my batteries are telling my inverters to shut down because they are low I need a way to tell my inverters to ignore it. If I can only run my 10K battery to 20%, then I only have an 8K battery. That 2K could be the difference between having power and not having power.

 

[HighTechLab]

I am still looking into this. For the record though, the batteries do not tell the inverter to turn off - they tell the inverter to use grid power if it's available. In a grid-down situation you would still be able to drain until LVP.

 

[Watts Happening]

I am still looking into this. For the record though, the batteries do not tell the inverter to turn off - they tell the inverter to use grid power if it's available. In a grid-down situation you would still be able to drain until LVP.

Much appreciated. If there is anything I can do on my end to be of assistance, please don’t hesitate to let me know. More than happy to test in whatever way needed.

 

[myles]

Alrighty, I'll give her a solid charge and see if I can't get it back in line.

What is your pack voltage when the state of charge causes it to pull from grid?


I only use battery voltage on my solark 15k, I don't use communications, frankly i don't like the complexity of communications, let the BMS do its job instead of the inverter do the bms's job, if your packs are reasonably balanced you won't have an issue. i've been running "headless" for a year and a half without any issues.

One thing i've noticed with the 15k, some of the settings need to be changed in the both the "grayed out" tab, and the primary tab to actually make a change. for instance, charge from generator amperage, there is a glitch which i mention in my youtube video in my signature that needs to be changed in the greyed out and the white one by enabling the greyed out setting in order to make the change otherwise gen charge amperage is not correct.

 

[Watts Happening]

I've had some similar issues with my batteries. I think if I tell my inverter to take the batteries to 1 effing percent, then they should run until it gets to 1 effing percent. I think if my batteries are telling my inverters to shut down because they are low I need a way to tell my inverters to ignore it. If I can only run my 10K battery to 20%, then I only have an 8K battery. That 2K could be the difference between having power and not having power.

Generally I feel the same way. In practical terms I’m sure the batteries would indeed continue discharging if the grid were down, and that makes me happy.

The “problem” we’re having is two fold, there are many days where the difference between switching to grid at 20% vs let’s say 10% is the difference between using grid power and not using grid power at all that day. Then we only have 80% to fill rather than 90% and we end up with a full bank at say noon or 1pm and our panels have little to do for the next few hours.

The real solution here is a larger battery bank, it obviously makes the most sense and is ultimately what I intend to do, but we run into problems there too. With this UL9540 nonsense, I can’t just have “as big of a battery as I want”, I can only have (3) batteries in a stack, then a 3 foot separation and again another (3) batteries. The location of our system just really doesn’t play well with that idea so I’m in a bit of a pickle.

I can either break the “law”, which truth be told I don’t care about, it’s the insurance side of things I fear in a worst case scenario. Or I can look into something like the EG4 power wall battery as it’s form factor would work where I have space. But this isn’t ideal either, I’m not aware of a way I can have both battery banks communicate in closed loop with the Sol-Ark.

Thus my decision to wait, if we can figure out the SOC portion I’ll just buy a couple more SOK batteries and “roll the dice” legally speaking. If not, and I have to rely on voltages and not have closed loop, then maybe my best move is the power wall. I’d be legal, and it should all work. Decisions decisions.

 

[Watts Happening]

What is your pack voltage when the state of charge causes it to pull from grid?


I only use battery voltage on my solark 15k, I don't use communications, frankly i don't like the complexity of communications, let the BMS do its job instead of the inverter do the bms's job, if your packs are reasonably balanced you won't have an issue. i've been running "headless" for a year and a half without any issues.

One thing i've noticed with the 15k, some of the settings need to be changed in the both the "grayed out" tab, and the primary tab to actually make a change. for instance, charge from generator amperage, there is a glitch which i mention in my youtube video in my signature that needs to be changed in the greyed out and the white one by enabling the greyed out setting in order to make the change otherwise gen charge amperage is not correct.

I haven’t checked that, but I can verify that simply removing the communication cable does allow the batteries to be further discharged. That was one of the tests Sol-Ark ran and they happily kept providing power.