I repeatedly see low battery alarm in my system and don’t have a clue where it can come from.
My configuration is as follows:
3 Pytes V5 Batteries, connected on DC side to three Victron MP II 48/4k5/55-32 running in 3phase config. On the AC side there is an 3phase solar inverter connected. All Loads are connected on AC-in. Both AC-out are unconnected (despite N-Connection which is connected between the MP’s)
The communication is set up via a CerboGX MK2, all components can be seen an administered from there.
Master of ESS is Pytes. (automatically selected), so I would expect that maximum discharge current is limited by Pytes automatically (?)
Max. current for loading is set to 70A (as Pytes says max.75 A are allowed)
The system was running quite well while loading and charging. After (firstly) connecting a car via wallbox the energy first was taken out of the batteries and the solar inverter. Out of a sudden no energy was taken from batteries any longer, but from grid.
Since then, the low battery alarm was raised by the master MP and is now coming repeatedly.
Measurement on the DC side shows, that the voltage goes down to ~19V and raises to ~55V after a short while again. In this case the alarm stops and 5-10 min later the same cycle starts again.
All FW versions are on actual state, possible cabling faults are checked and no errors found.
The Pytes Data in CerboGX shows no faults, according to the transmitted status, everything on battery-side looks good but the battery remains in idle mode and is neither loading nor charging.
What can cause this behavior and how can I heal it ?
If you need further data, don’t hesitate to ask, I will deliver what’s needed.
Thanks in advance for your highly appreciated help
During the night I switched off my system to prevent unattended faults.
This morning I switched on the Pytes V5 while the MP’s remained off. Measurement on DC bus shows a voltage of 1.2V. I have the feeling that the transmitted status from the Pytes batteries is not correct and somehow yesterday’s discharging didn’t stop at Minimum SoC (20%) but led to complete discharge of the batteries. What I don’t know is what to do now to get the system running again and in future to prevent the next fault…
In the GX have you in system set up marked the system as having no loads on the output.
Yeah not a normal wiring convention. The neutral is always combined at the main DB. (Not usually connected/commoned on the input and the output.) In your case there are no loads on the output so no wires should be connected there at all.
Might not be programmed to or have the ability to transmit anything about that. And that isa firmware issue so out of the end user control or influence normally.
So their output is not right and they are reporting their pack voltage to the GX before the bms disconnect not uncommon.
What is happening or so it appears if there is no output, is your battery pack is shutting down its output in protection.
For three batteries that is not correct. Are they all online on the GX? That seems small it should be 3x70/75A
As an FYI your battery bank is too small for your system size with 3 batteries only.
Using SOC relies on the fact that the battery is correct about its soc.
Ess uses voltage so maybe raise the low cut off a bit.
At low SOC the chances of a low cell tripoing the system is higher, so the possibility is that the pack or pack have one cell that is low and that is the cause of the issues here.
That would be my first suspect here.
on the AC-out I only connected the N-contacts of the MP’s with no connection to AC-in because I found that advise in the installation manual of a 3phase system. To be honest I didn’t really understand the sense of this measure, but it shouldn’t hurt…
What do you mean with “might not be programmed or have the ability to transmit anything” ? Before the low voltage fault occurred, the data was consistend and logical. So I don’t expect to have a transmission problem between Cerbo and Pytes. I have the feeling Pytes is thinking everything is fine, but in fact it isn’t. Unfortunately there is no reset-button to start the SW from scratch…
If the battery is shutting down its output: How can I force the output to go online in order to have the chance of loading the batteries ?
All three batteries are shown in Cerbo, yes. And it’s also reported there that no cell is blocking carging or loading, the rest of the indicators shows “OK”
I had chosen 70A to be on the save side when starting the system. The plan was to increase that later.
I agree, there must be a fault inside the batteries, maybe a mismatch between reported status and reality.
The question is how can I solve that - just by raising Minimum SOC to >20%, maybe 50% for the start ?
First the batteries should be forced to check the status and correct it, or am I wrong ?
Do you see anything on the cell min and max in the vrm advanced?
Usually imbalances happen because cells are imabalnced or unwell (i don’t think you are at that point) batteries aren’t balancing and batteries normally only balance at 90 to 100% or in absorption soc. Do you regularly charge to 100%?
As I checked the complete configuration of ESS, Cerbo and MP’s and everything looked fine, I (again) started searching for other faults.
In short: there was a hidden fault in the cable between battery and Lynx PowerIn. This caused the voltage to toggle or break down completely, depending on the position of the cable. I found this because I was checking, if all screws are fixed.
So Thanks a LOT for your highly appreciated help, LX !!!
In the end it was quite easy to fix, but hard to find. BTW: now that the cable is fine, the measurement between MP and batteries differ only by a few 1/10 V
Maybe this can be used by others in case such a behaviour occurs somewhere…