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Narada low voltage issue


Jay-Dee
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Hoping someone has some insight for me on an odd problem... The last two days, my system is switching back to grid from battery mode in the early mornings. This is caused by the batteries hitting a low voltage of 44v in a sudden drop. As you can see from the below graphs, the steep decline is not caused by an increase in usage or drop in temperature. The final drop was caused by an increase in load when we got up this morning but that does not explain what happened for the hour before which lead to the problem.

This has happened once or twice before but on days when the batteries were not fully charge on the previous day and I put it down to the voltage perhaps not have hit it proper levels but the last two days have been reasonable weather and although only achieving a full charge late in the afternoon, we still got there.

Any ideas as to why this could be happening and how I prevent it?

 

 

Screenshot 2020-12-11 at 06.08.41.png

Screenshot 2020-12-11 at 06.09.26.png

Screenshot 2020-12-11 at 06.20.58.png

Edited by Jay-Dee
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That battery voltage curve is typical of a lithium battery being completely discharged. i.e. The voltage remains pretty flat until the battery is close to empty and then the voltage starts dropping rapidly. This should not happen at 50%SOC. How are you reading SOC? i.e. Do you have comms to the battery itself or are you using a 3rd party device like a Victron BMV to measure energy in and out? Do you have more than 1 battery in parallel? If you have 2 for example, then maybe there is a bad connection on 1 of them so you are only using 1 of the batteries and therefore only have half the capacity available (hence being empty at 50%)

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52 minutes ago, Stanley said:

That battery voltage curve is typical of a lithium battery being completely discharged. i.e. The voltage remains pretty flat until the battery is close to empty and then the voltage starts dropping rapidly. This should not happen at 50%SOC. How are you reading SOC? i.e. Do you have comms to the battery itself or are you using a 3rd party device like a Victron BMV to measure energy in and out? Do you have more than 1 battery in parallel? If you have 2 for example, then maybe there is a bad connection on 1 of them so you are only using 1 of the batteries and therefore only have half the capacity available (hence being empty at 50%)

Thank you for the insight... I had not looked at the curve from that perspective.

I am running 2 batteries in parallel with BMS comms between them and then comms back to my ICC, so the readings are coming directly from the batteries.

You got me thinking and I recently mounted the batteries on wall mount brackets and check the cabling this morning... The one negative cable, although making a solid connect is loose. I am going to put it some locking washers in an hour or so and will keep an eye on it.. I did put a meter to both batteries and I am getting current form both batteries although 2A difference (lower from the loose connection) and this makes me think even more that this could be causing the issue as the voltage drops the difference becomes too much

 

Will keep you posted and thanks again!

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Perhaps somebody who knows ICC well can answer this question then:

If ICC is communicating with 2 batteries and 1 reports 100% SOC and the other 0%, will ICC report 50% SOC (i.e. The average of the 2)?

A loose connection could definitely cause low voltage issues, let's hope that's all it is and the fix is as simple as a lock washer.

Good luck

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7 minutes ago, Stanley said:

Perhaps somebody who knows ICC well can answer this question then:

If ICC is communicating with 2 batteries and 1 reports 100% SOC and the other 0%, will ICC report 50% SOC (i.e. The average of the 2)?

A loose connection could definitely cause low voltage issues, let's hope that's all it is and the fix is as simple as a lock washer.

Good luck

So I have already chatted to Manie from ICC when installing the batteries and ICC only reads from 1 on the Narada's... Apparently (I cant personally confirm), the way the Narada's communicate is different to Pylontec in the sense that while they talk to each other the reporting back to ICC is only of the battery which you are plugged into and not the combination of all. In theory this will not make a difference as they should be balanced / equal but I know it is something they are looking further into as they have been pulling logs from my system.

As a precaution, I did also change the BMS cable into 2nd battery (with the tighter cable) but the readings are the same at the moment

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I would not let a 15S LFP battery drop below about 47.5 V; certainly never as low as 44 V.

Don't trust the SOC reading on the inverter, and only from ICC if it is getting that SOC from the battery's BMS. The inverter will be doing a rough estimation based on battery voltage alone, and assuming lead acid chemistry.

At 100% SOC, I would expect a higher battery voltage than 50.0 V, and as pointed out already, it can't possibly be at 50% SOC when the battery voltage is at 44 V. 44 V is about 2% SOC; dangerously low. So something is screwed up, for sure.

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On 2020/12/11 at 8:51 AM, Stanley said:

A loose connection could definitely cause low voltage issues, let's hope that's all it is and the fix is as simple as a lock washer.

Sadly or fortunately... Which ever way one wishes to look at it.. This was not the problem. While it was loose, it was not enough to cause an issue.

In the process, I actually split the batteries and put a meter on each and both had the same low voltage readings while the SOC from the BMS (and SOC lights) were high

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On 2020/12/11 at 2:36 PM, Coulomb said:

I would not let a 15S LFP battery drop below about 47.5 V; certainly never as low as 44 V.

Don't trust the SOC reading on the inverter, and only from ICC if it is getting that SOC from the battery's BMS. The inverter will be doing a rough estimation based on battery voltage alone, and assuming lead acid chemistry.

At 100% SOC, I would expect a higher battery voltage than 50.0 V, and as pointed out already, it can't possibly be at 50% SOC when the battery voltage is at 44 V. 44 V is about 2% SOC; dangerously low. So something is screwed up, for sure.

I fully agree these low voltage readings are extremely concerning. I decided to fully charge the batteries from grid for the first time in a while. From the below, you can see that while the SOC hit 100% at around 22:55 it only stopped charging the battery around 01:10 when it hit the bulk charge 52.5v and then returned to the floating 51.4v

1430971877_Screenshot2020-12-12at05_01_49.thumb.png.ac2735f685d68ec211da3bc1f2dd2ac6.png

 

Since fully charging on Saturday, I have then run off grid again and you can see things are running a lot more "normal". This morning when pulling the below, you can see we are back just under 50% SOC and the voltage is sitting around 49v

917112598_Screenshot2020-12-13at05_46_04.thumb.png.8f845befd3e5331d657bb2dbcf96f8fa.png

 

So while this now returns my system to what was normal behaviour, it got me thinking. The reason my bulk charge (52.5v) and float (51.4v) were set this "low" is that higher caused by PV to cut to 0w every few seconds once it hit 100%. This was solved with tweaking the settings but now I know that this could have been a firmware issue which has been fixed by v71.94 which I updated to recent.

A while back, @Coulomb... You suggested that I run my Narada batteries with the same values of Pylontec's (52.5v & 51.8v). Would this still be your recommendation, now that I have 2 connected? 

Battery Spec - http://narada-ap.com/wp-content/uploads/2016/04/48NPFC100.pdf 

 

In the meanwhile, I am going to raise the float value, to see if the initial PV cutoff problem returns but your input is always greatly appreciated.

 

Bottom line for anyone else having this problem in future... Fully charge your batteries from grid every now and then... Also 100% SOC is not fully charged 🤣

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4 hours ago, Jay-Dee said:

You suggested that I run my Narada batteries with the same values of Pylontec's (52.5v & 51.8v). Would this still be your recommendation, now that I have 2 connected? 

Yes, although you may need to tweak the values somewhat. My recollection is that the float voltage (51.8 V, 3.45 VPC) is so high (relative to what I'd prefer to see, 3.356 VPC) because Pylontechs need to stay above a certain voltage for balancing to occur, and 3.356 VPC isn't enough. I have no idea what voltage balancing occurs at with the Narada BMS, and it seems to be a Herculian task to find this sort of information.

My other thought is that your battery isn't getting a full charge. Could it be an Axpert inverter-charger with the premature float bug? If so, perhaps consider patched firmware if available, or one of the other workarounds (timed absorb or frequent equalising with the equalisation voltage set to the same as the bulk/absorb setting).

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1 hour ago, Coulomb said:

Yes, although you may need to tweak the values somewhat. My recollection is that the float voltage (51.8 V, 3.45 VPC) is so high (relative to what I'd prefer to see, 3.356 VPC) because Pylontechs need to stay above a certain voltage for balancing to occur, and 3.356 VPC isn't enough. I have no idea what voltage balancing occurs at with the Narada BMS, and it seems to be a Herculian task to find this sort of information.

My other thought is that your battery isn't getting a full charge. Could it be an Axpert inverter-charger with the premature float bug? If so, perhaps consider patched firmware if available, or one of the other workarounds (timed absorb or frequent equalising with the equalisation voltage set to the same as the bulk/absorb setting).

That you as always! Reading through the spec's, I can see that the charge voltage quoted is supposed to be 54±0.5V... This is also making me think that my settings are off and perhaps the Narada's need higher voltage like the Pylontechs. I am going to play around and see

Re the float bug... How would one tell if my inverter suffers from this?

Lastly, how often would you recommend equalising without a float bug vs with a float bug?

Thanks in advance!

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3 hours ago, Jay-Dee said:

Re the float bug... How would one tell if my inverter suffers from this?

Basically, if it's an Axpert/RCT/Mecer/etc made by Voltronic, and you didn't put patched firmware in there, it has the bug. Sadly.

You can convince yourself by following the steps in this post.

3 hours ago, Jay-Dee said:

Lastly, how often would you recommend equalising without a float bug vs with a float bug?

If you don't have the float bug, never equalise (assuming an LFP battery).

If you have the float bug, every day or possibly every second day. It would be a bit like that utility charge you did recently, except completely automatic.

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37 minutes ago, Coulomb said:

Basically, if it's an Axpert/RCT/Mecer/etc made by Voltronic, and you didn't put patched firmware in there, it has the bug. Sadly.

I have an Axpert King 5K with firmware version 71.94.. Is there a patched firmware for this unit that also has the utility charge / no utility charge issue fixed?

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22 hours ago, Jay-Dee said:

I have an Axpert King 5K with firmware version 71.94.. Is there a patched firmware for this unit that also has the utility charge / no utility charge issue fixed?

No, not yet. Now that the firmware seems to have settled (71.94 has been out a while now), it looks like the time is near when Weber and I will take on a fully patched firmware. I might be able to do a partial patch (just doing the two premature float bugs) before then, I'll see.

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5 hours ago, Coulomb said:

No, not yet. Now that the firmware seems to have settled (71.94 has been out a while now), it looks like the time is near when Weber and I will take on a fully patched firmware. I might be able to do a partial patch (just doing the two premature float bugs) before then, I'll see.

Thank you in advance... I will definitely be keeping an eye out for that.

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