funny enough again, some days sync happened but voltage didn’t reach 56v
What happened these days? Soc didn’t went under 70%
I think I found some sort of bug? How do I call Victron’s attention to this?
I have drawn it to their attention through other channels
I can confirm this situation. I have a recent NG system not synchronizing even though the conditions all seem to be met: 56V, <8A, 3min. The manual warns for this situation when irregular changing/discharging currents are present. It does not however explain the mechanics as to why this can happen. The hypothesis that the voltage is not a stable 56V as a result of the irregular currents. Each time it drops to say 55.99V it resets the timer and the 3 minutes is never reached. I set the monitoring voltage to 55.9V and now it synchronizes. I think any voltage between the float value and the absorption value will work (54.8-56V). I hope Victron addresses this such that it works with the default settings, even in the presence of irregular currents.
the odd thing is this didn’t happen when I had a 3 phase system. Now that I changed to parallel, it happens.
Now, wanna see something funny?
For almost 1 week the system won’t reach 56V
I think because the SoC won’t drop under the SoC threshold.
And because I dropped the Charged voltage to 55,5V it sync well the first day after the SoC went under the threshold.
then it stopped sync because it never again reached 55,5V
Now, a solution for the sync would be set the charged voltage to 54,5 or 54,7V
Not sure what to do now…I’m ok to the pack not being elevated to 56V, I see the cells can balance well…
Ahh damn it. I lowered the threshold to 60%, the charged voltage to 54,7V with tail current at 3% and time 5 minutes, manually resynced and lets see the next days
I think what you see here is behaviour as documented. It does not cycle because it does not go under the SOC limit you set and the set period (30d by default) has not been reached.
The drift is quite significant thought. Perhaps it is better to reduce the periode from 30 to maybe 7 days, if you care about the SOC % to be accurate?
Mind that the battery is always elevated to 56V as that is what the battery itself tells the BMS to do. The only thing you can influence is at what voltage it detects 100% charged. (That is ‘charged voltage’).
One more question for you: when the SOC falls below the level you choose (70 - 60%) and the full cycles charge is triggered, do you also see a very long absorption phase of 5, 6 or more hours?
As a side note: are you aware that the default update of VRM is something like 5 minutes and that the lowest you can set is 1 minute? This will significantly reduce the resolution of the graphs. Hence it is hard (impossible?) to tell if, as you asked, the voltage reaches 56V or not and a sync should happen.
3 posts were merged into an existing topic: Experience with absorption time with NG lithium batteries with Lynx NG BMS
New topic created
I lowered the “sync/charged voltage” to 54,7V, It will sync everyday now. I just need to keep an eye on the cell voltages and see if I need to force absorption sooner. Indeed, maybe the 7 days is not a bad idea. We see how will it evolve.
Why did you change it to so low a setting? It is even lower than the float value. I cannot oversee the consequences but I wouldn’t do that.
What is your reasoning behind setting that value?
Because if I’m not going under the threshold, the sync must happen just under the highest voltage of the day.
And if sync and the transition from Abs to Float is a different matter and are not related, this is the only way to sync everyday.
Ah, here is you reasoning. I believe you really should leave the charged voltage setting higher than the float voltage and use the other settings to have it absorb every 7 days (or even less) for say, 30 minutes. Then if that is not enough for balancing, increase it.
Victron suggests 2h in 30 days, so keeping that ratio constant seems a reasonable thing to do as a starter. That is why I suggest 30 minutes 7 days.
Maybe even 4 days / 15 minutes will also work.
If you do so, you are operating with the general framework Victron provides for handling this. Setting the detection voltage lower than the float voltage brings you into unknown territory. That is probably why I hesitate a bit.
I understand this, but looking back in March or what it was, I had weeks at 56V. I much more prefer the 54,8V.
I’ll keep an eye at the cells, and either way if they unbalance, I expect the BMS to trigger 56V directly.
Look here so many days in a row the battery was taken to 56V
Setting it lower won’t cause damage. I’ll try for a few days. for science 
Are you trying to avoid the endless absorption this way?
Regarding your remark that sync happens without 56V being reached and the accompanying graph: as far as I can tell from that graph it did go to 56V after every discharge below 70% and subsequently it synced. There are some point at which a spike up is seen but 56V is not reached. However, the spike is there and I suspect the graph resolution is playing parts here. You mentioned using home assistant and I have in my (long) carrier not met programmers that could reliably (with proper math) scale graphs based on sampling. Actually, up till now, Victron has positively surprised me. In short: short spikes often disappear, but to me the graph looks OK.
Also, sometimes syncing does work and a very short absorption follows instead of many hours. This is consistent with my hypothesis (which we share) about the underlying problem. Is is after all also a matter of statistics and it is very well possible that syncing does see a 3 minute 56V period that satisfies it. Same for absorption.
Yes, I would love to set my cells max voltage at 3.45V
I can’t find a way to do it with these NG. If I knew what I know today I wouldn’t had bought Victron batteries.
This being said I’m not displeased. I’d just prefer to have the option to manage the cells at a lower voltage than Victron forces me.
If this trick allows me to keep the cells near this 3.425 I’ll prefer than keeping it at 3.50.
Yesterday I lowered the HA resolution to 10 sec.
Today we will see the sync without 56v, I hope.
I left home 10 min ago and for sure for several hours I won’t be home. More yo the story in the end of the day
