Random cell voltage drops

luphi · March 8, 2023, 8:04am

I’m running 2 cellmate-k9 connected each to a 16s eve lf280k LiFePO4 battery pack.
Every coupe of days I receive an alarm regarding low battery voltage. 1st investigation shows a short voltage drop in one of the cells:

Batrium is showing a voltage drop down to 1,8V but Victron is showing just 2.3V. This might be related to the just 1minute resolution at Victron.

Anyway, I’m afraid, that I have a bad balance lead. I manually soldered inline fuses directly to the ring lugs.
What is the best way to identify the bad guy?

luphi · March 8, 2023, 8:06am

Since I’m a new user, I’m not allowed to add multiple pictures in a single post

luphi · March 8, 2023, 8:07am

Renzee · March 9, 2023, 6:02am

Hi @luphi,

Maybe it’s best if we direct this technical enquiry to our Batrium support team via email as we cannot be certain of what is happening without more information about your setup.

Can you let us know what hardware you got and the software and the firmware version (build) you are currently using?

It might be best to send us a manual extract report and send it to our tech support email so we can have a look at your configuration.

luphi · March 9, 2023, 7:36am

Hi @Renzee ,

thank you for your quick response.
Just send the email.
You also should receive an email from Victron VRM, which invites you to my Victron setup.

Cheers,
luphi

physi · March 10, 2023, 11:27am

I would like to hear, when something is found out, because I have the same issue “sometimes”.

luphi · March 10, 2023, 11:29am

got an answer by email this morning:

Currently, we are working with Victron directly, revising some algorithm issues that might be helpful in resolving this.
Alternatively, a new firmware version will be released very soon that hopefully might address this.
We’ll keep you posted for updates.

luphi · March 12, 2023, 6:12pm

yesterday or the day before, I was lucky. I had the watchmon toolkit open monitoring the cells while it happend again.
For a blink of an eye one cell disappeared and I was able to identify it’s number.
So, I went to the battery to check the balance lead and al screws of that particular cell and also it’s neighbors, unfortunately everything seamed to be fine
For me, it looks like Victron is not involved at all, maybe an issue with the K9?

Cheers,
luphi

slimf · March 29, 2023, 8:00am

I have an issue towards the top of charge (when balancing) where a cell will briefly display WAY over its real voltage - For example, a cell might be at 4.11v and all of a sudden will appear as 4.5v – but only briefly. Its some sort of phantom interference. Its not the Victron integration, as I can see the voltages in the watchmon toolkit.

If I had to guess, Batrium will be applying some sort of averaging technique to eradicate these erroneous spikes/dips.

physi · April 18, 2023, 6:44am

Same Problem here today, which causes my Main Switch to cutoff everything…
Luckily a snaphot was generated, which shows a CellVoltage of 1.76V on my Cell 1 (LFP).
Now the cell is back to “normal” 3.3V.

So how should one handle this?
Turn of the critical LowVoltage Watch? Or is there a way to wait for at least xseconds before the criticalOffline State is triggered?

OpStatus AuthMode CMU Mode
CriticalOffline Default Normal

SysFaults: Nil

Live status information
Min @ ID Max @ ID Avg Repeat
CellVolt 1.76v @ 1 3.30v @ 3 3.26v 143

luphi · April 18, 2023, 7:12am

You can play with the delay transition stop values

That is exactly what you are asking for.
But that is just fighting symptoms and should be just treated as a workaround
In my point of view this is a measurement fault. Are you using K9 or individual CellMons?

Cheers,
luphi

physi · April 18, 2023, 7:45am

That value is 120sec in my System, I use CellmatesK9.
I turned on the critical Main Switch last weekend, before I monitored some LowVoltage issues too, randomly spreaded over different cells.
I agree, this must be an K9 issue, but I will check my connections on that cell again…

User_NRW · May 2, 2023, 4:17pm

have the same issue with 2.17.28.
4 banks 16S1P, randomly false measuring on cell 1 of each K9 for two cycles release the shunt trip.

Hopeful 2.17.39 fixes this bug. Will test the next days.

physi · May 5, 2023, 10:17am

Yesterday, again CellDrop even with 2.17.39.

I’ve recorded via mqtt and Node-Red all drops below 2.8V.

My Cellmates are
HW9.0 FW0.7 BL160.15

But because I turned off Low Cell Volt Monitor, no Critical event was reported.

But I’m not brave enough to reactivate the Relay Trigger to the Main Switch, because I don’t like BlackOuts because of false positive measurements.

Renzee · May 11, 2023, 6:44am

@physi Thanks for this information. I have forwarded this to our tech team.

The timestamp has been helpful, indicating that it drops for 4 secs and then recovers. We now have something to help us investigate this issue.

luphi · May 11, 2023, 6:56am

Would you mind to explain, how to setup this up, so I can reproduce it in my installation.
I have a very good understanding of Linux but never used Node Red nor MQTT.

physi · May 11, 2023, 7:00am

@Renzee here are some more data, maybe that will be helpful as well.
The 4 sec. seems to be right in each drop.

{
	"c": {
		"1.73": {
			"1": [
				"2023-05-04T16:55:37.041Z",
				"2023-05-04T16:55:37.081Z"
			]
		},
		"1.49": {
			"1": [
				"2023-05-04T16:55:37.631Z",
				"2023-05-04T16:55:37.672Z",
				"2023-05-04T16:55:38.217Z",
				"2023-05-04T16:55:38.258Z",
				"2023-05-04T16:55:38.805Z",
				"2023-05-04T16:55:38.846Z",
				"2023-05-04T16:55:39.397Z",
				"2023-05-04T16:55:39.438Z",
				"2023-05-04T16:55:39.986Z",
				"2023-05-04T16:55:40.027Z",
				"2023-05-04T16:55:40.574Z",
				"2023-05-04T16:55:40.615Z",
				"2023-05-04T16:55:41.163Z",
				"2023-05-04T16:55:41.204Z"
			]
		},
		"2.695": {
			"1": [
				"2023-05-04T16:55:41.750Z",
				"2023-05-04T16:55:41.790Z"
			]
		},
		"1.95": {
			"1": [
				"2023-05-06T06:42:28.578Z",
				"2023-05-06T06:42:28.618Z",
				"2023-05-08T15:52:27.992Z",
				"2023-05-08T15:52:28.032Z"
			]
		},
		"2.185": {
			"1": [
				"2023-05-06T06:42:29.164Z",
				"2023-05-06T06:42:29.205Z"
			]
		},
		"2.195": {
			"1": [
				"2023-05-08T15:52:23.278Z",
				"2023-05-08T15:52:23.318Z"
			]
		},
		"1.465": {
			"1": [
				"2023-05-08T15:52:23.868Z",
				"2023-05-08T15:52:23.910Z",
				"2023-05-08T15:52:24.455Z",
				"2023-05-08T15:52:24.495Z",
				"2023-05-08T15:52:25.042Z",
				"2023-05-08T15:52:25.083Z",
				"2023-05-08T15:52:25.641Z",
				"2023-05-08T15:52:25.682Z",
				"2023-05-08T15:52:26.228Z",
				"2023-05-08T15:52:26.269Z",
				"2023-05-08T15:52:26.817Z",
				"2023-05-08T15:52:26.858Z",
				"2023-05-08T15:52:27.403Z",
				"2023-05-08T15:52:27.444Z"
			]
		},
		"2.595": {
			"1": [
				"2023-05-10T05:24:52.337Z",
				"2023-05-10T05:24:52.377Z"
			]
		},
		"1.45": {
			"1": [
				"2023-05-10T05:24:52.924Z",
				"2023-05-10T05:24:52.965Z",
				"2023-05-10T05:24:53.511Z",
				"2023-05-10T05:24:53.552Z",
				"2023-05-10T05:24:54.101Z",
				"2023-05-10T05:24:54.141Z",
				"2023-05-10T05:24:54.689Z",
				"2023-05-10T05:24:54.730Z",
				"2023-05-10T05:24:55.325Z",
				"2023-05-10T05:24:55.366Z",
				"2023-05-10T05:24:55.916Z",
				"2023-05-10T05:24:55.957Z",
				"2023-05-10T05:24:56.509Z",
				"2023-05-10T05:24:56.550Z"
			]
		},
		"2.14": {
			"1": [
				"2023-05-10T05:24:57.228Z",
				"2023-05-10T05:24:57.269Z"
			]
		}
	}
}

luphi · May 11, 2023, 7:20am

Keep in mind, hat you just count the time while the cell is below 2.8V but usually it starts dropping from 3.2 to 3.3V. That will give you probably a drop time of 5 sec, which then fits to the K9’s 5 sec measurement cycle.
Just my two cents

luphi · May 11, 2023, 10:59am

just happened also to me at 12:07 local time.
SOC 80%
current -5 Amps
So, definitely no bypassing
You can clearly see it in VRM.

Hope that helps.

luphi · May 12, 2023, 7:05am

Once more, this morning at 5:54