Battery unexpectedly dropping to 0% SOC

[Grant27]

Hi all.

I have a 5kW Deye Inverter with three Pylontech US3000C batteries. On a few occasions over the past two weeks the battery SOC has dropped from around 20 or 30% to zero in a matter of seconds (see attached screenshots). Can anyone advise on what could be causing this? Is there possibly a setting that is not set correctly?

[Nexuss]

I have seen this before on Solarman . It turned out to be a logging issue as the batteries were still all on the SOC that the logger was at before it went to zero. When you see it happening again just go check on the batteries to make sure they all still have the same SOC lights on,if they still have SOC lights on and are not really empty you can usually rule out battery problems.  

[Grant27]

Thanks for the advice, Nexuss. I will keep an eye on it and compare the SOC lights on the batteries themselves if it happens again.

[Grant27]

Hi everyone.

I had the same issue again this morning... batteries were at 22% at 05:30 then at 0% by 05:35 (see attached screenshot). I checked the physical batteries (as suggested by Nexuss) but they were completely dead. They stayed on 0% until 07:30 at which time they started charging (I assume this is when there was enough PV).

What I find odd is that it is happening randomly (every 2 - 4 days) and always between 5am and 7am. The rest of the time everything works perfectly.

Has anyone else experienced this issue? Is it possibly something to do with my battery settings? (I have attached my settings below for you to view).

Any suggestions / recommendations would be welcome.

[Nexuss]

4 minutes ago, Grant27 said:

Hi everyone.

I had the same issue again this morning... batteries were at 22% at 05:30 then at 0% by 05:35 (see attached screenshot). I checked the physical batteries (as suggested by Nexuss) but they were completely dead. They stayed on 0% until 07:30 at which time they started charging (I assume this is when there was enough PV).

What I find odd is that it is happening randomly (every 2 - 4 days) and always between 5am and 7am. The rest of the time everything works perfectly.

Has anyone else experienced this issue? Is it possibly something to do with my battery settings? (I have attached my settings below for you to view).

Any suggestions / recommendations would be welcome.

Did the system actually shut down ?  Were the Run lights on the batteries still flashing ? no red light alarms? No SOC lights could also mean they are in idle mode but then the run lights should still flash. When it starts charging again can you show the graph as the soc rises ? does it go up gradually from 0% or does it jump up rapidly at any stage(it looks like its jumping up rapidly when its starting to charge but hard to see from your picture.

[Scorp007]

Try upping your 0h-04h and 04h-08h to 25% and see if it prevents this problem. 

Also tick Use Grid for these times. 

Edited May 12, 2023 by Scorp007

[Grant27]

No, the inverter did not shut down, it was still running. Only the battey was showing 0% charged.

There were no error / alarm lights on the batteries - below is a photo I took of the physical batteries...

[Grant27]

7 minutes ago, Scorp007 said:

Try upping your 0h-04h and 04h-08h to 25% and see if it prevents this problem. 

Also tick Use Grid for these times. 

Thanks Scorp007, I will change those settings and monitor for a few days to see if it resolves this problem.

[Nexuss]

9 minutes ago, Grant27 said:

No, the inverter did not shut down, it was still running. Only the battey was showing 0% charged.

There were no error / alarm lights on the batteries - below is a photo I took of the physical batteries...

Ok i see , that middle older battery is probably draining faster than the other 2 and causing the SOC to bug out if i had to guess ,As @Scorp007 mentioned raising the minimum SOC will likely solve the issue. You can also use batteryview software to monitor the batteries while they are at 15-20% to see exactly what is happening with that older battery.Edit * i just remembered the older US3000 series was only 80% DOD batteries which is maybe why this is happening.

Edited May 12, 2023 by Nexuss

[Grant27]

Yes, one of the batteries is about 4 years old, the other two were purchased within the last month. What you are saying certainly makes sense, I am sure the older battery is draining faster than the new ones. I have made the setting changes suggested by @Scorp007, so hopefully that will help as I am concerned that this issue might be damaging the batteries. I will search for batteryview software and see if that gives me a bit of insight.

Thanks to you and @Scorp007 for all the assistance, much appreciated.

[Eurard]

Will the middle placement of the older battery also not play a small role?

[Grant27]

22 minutes ago, Eurard said:

Will the middle placement of the older battery also not play a small role?

I have no idea, but if all three batteries are now behaving as one I would think the placement/order of the batteries would make little difference.

This is how our installer set it up when we recently upgraded from one battery to three.

Are there any experts out there who can comment on this?

 

[Nexuss]

1 hour ago, Grant27 said:

Yes, one of the batteries is about 4 years old, the other two were purchased within the last month.

Ah ok that makes sense , that is quite a big age difference... that one battery is going to be limiting the 2 new ones quite a bit unfortunately,so your minimum SOC will have to be set higher than 20% maybe even 30%. Depending on how tech savvy you are it may be worthit to update each battery with the latest firmware ,i have read on this forum that the older 80% DOD US series gets updated to 95% DOD with newer firmware but i dont know if this is true. Do some good research before you attempt this ,all the info you need is on this forum.

 

[Grant27]

1 hour ago, Nexuss said:

Ah ok that makes sense , that is quite a big age difference... that one battery is going to be limiting the 2 new ones quite a bit unfortunately,so your minimum SOC will have to be set higher than 20% maybe even 30%. Depending on how tech savvy you are it may be worthit to update each battery with the latest firmware ,i have read on this forum that the older 80% DOD US series gets updated to 95% DOD with newer firmware but i dont know if this is true. Do some good research before you attempt this ,all the info you need is on this forum.

 

 

2 hours ago, Nexuss said:

Ah ok that makes sense , that is quite a big age difference... that one battery is going to be limiting the 2 new ones quite a bit unfortunately,so your minimum SOC will have to be set higher than 20% maybe even 30%. Depending on how tech savvy you are it may be worthit to update each battery with the latest firmware ,i have read on this forum that the older 80% DOD US series gets updated to 95% DOD with newer firmware but i dont know if this is true. Do some good research before you attempt this ,all the info you need is on this forum.

 

I am pretty tech savvy, but I would be a bit worried to attempt the firmware upgrade myself... these batteries are pretty expensive toys to break if something goes wrong!

I will ask my installer about it and see what experience he has had with upgrading firmware on older batteries.

In the meantime, I have set my minimum SOC to 25% and will monitor and see how things go.

[Tinbum]

3 hours ago, Grant27 said:

I have no idea, but if all three batteries are now behaving as one I would think the placement/order of the batteries would make little difference.

This is how our installer set it up when we recently upgraded from one battery to three.

Are there any experts out there who can comment on this?

 

That is correct placement.

[Tinbum]

2 hours ago, Nexuss said:

Ah ok that makes sense , that is quite a big age difference... that one battery is going to be limiting the 2 new ones quite a bit unfortunately,so your minimum SOC will have to be set higher than 20% maybe even 30%. Depending on how tech savvy you are it may be worthit to update each battery with the latest firmware ,i have read on this forum that the older 80% DOD US series gets updated to 95% DOD with newer firmware but i dont know if this is true. Do some good research before you attempt this ,all the info you need is on this forum.

 

Yes the old batteries didn't have the 95% DOD so I'm pretty certain that will  be causing the issue.

 

Can you show a graph of the SOC?

Edited May 12, 2023 by Tinbum

[Grant27]

1 hour ago, Tinbum said:

Yes the old batteries didn't have the 95% DOD so I'm pretty certain that will  be causing the issue.

 

Can you show a graph of the SOC?

@Tinbum below is a screenshot of the SOC today...

[Tinbum]

20 minutes ago, Grant27 said:

@Tinbum below is a screenshot of the SOC today...

It looks to be at about the 20% SOC so probably is the old battery limiting it via the bms.

[Grant27]

20 hours ago, Tinbum said:

It looks to be at about the 20% SOC so probably is the old battery limiting it via the bms.

Yes, that certainly makes sense. I have changed the minimum SOC to 25% and had no problems this morning. I'll keep an eye on it for a week or so to make sure the problem has gone away.