So, I just updated my BMS
Settings before
Settings after update and factory defauls loaded.
Let’s see what’s gonna happen tomorrow.
As above, remove any setting for “limit managed battery charge voltage” DVCC so it charges to 56.0V.
Although I promised to perform a test, I didn’t want to changes the settings again (it is a real pain in the a$$ to search for the right settings in different places) so I let it run with the ‘recommended values’.
It sync’d nicely around 13h45m.
It also did not have a prolonged absorption time.
Next will be the test with max charge voltage at 55V and monitoring voltage at 54.9V.
After that I am going to confirm if the absorption last longer when it is actually needed. Hard to test, because the batteries are and remain very well balanced.
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Your point about the battery balance applies to me, as soon as current tails off at 14.0V the cells are within 0.01V of each other.
Join the club 
I installed the firmware, reset to defaults to load the recommended values, removed the DVCC in the console and let it go.
Yesterday evening in the shower, (what other time would one think about the parameters in the BMS?) I remembered that I want the forced sync to happen seldom, because the cells are never (in my case) unbalanced; so today I lowered the SoC threshold from 70 to 50%, and I’m thinking to lower it to 40.
Other than that, it’s working as intended, finally…
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I ran for 6 days without an absorption going down to 45% and used about 1000Ah from 600Ah of batteries over that time and the cells were still balanced, only 3 mins at 14.0V, just enough time for the sync to 100%.
I already run months with the voltage limited; so no absorption. Never saw unbalance.
I see that your system had a very short peak to 56V and then sync’d to 100%. Congrats! 
You say you want to lower the SoC threshold to 40%, but I think this whole setting makes no sense. You could just as well set it to 99%.
The explanation say that “a new charge cycle will be initiated as soon as the battery state of charge drops below this threshold”. But a charge cycle is always initiated, as soon as there is solar power available, regardless the SoC. What they mean, I think, is that it continues charging to 56V, let it sync to 100% and then drop back to float, 54V again. And that it does that only after the threshold has been passed.
I escapes me why it not just always initiates a short peak to 56V and sync. That doesn’t harm the battery, gives always a fresh start from 100%. This whole complicated logic about doing that only after a drop below a threshold only introduces uncertainty about the SoC when it cycles between 100 and 80% for days in a row. It will drift at some point, and that drift accumulates. Now the first reaction would probably be: “then we create another option, a timeout, so that it also syncs after a number of days.” But that is like fighting complexity with more complexity. I believe the whole option could better be removed. Why is it there?
Charge to 56V, sync, drop back to 54V. Takes three minutes. That’s it.
You see, I am also installing this for others. Margins are thin and my time is limited. What about people asking: “why is my battery not 100% charged”. And all these settings… I have to be assured that it works after I installed it. When I have to return and mess with settings, my margin will soon be gone.
If the solar is properly managed by the BMS through DVCC then it does not start a new cycle daily. If you want a daily cycle either set the SOC threshold to 90% or something like thst or set the repeat absorption interval to 1 day. I found the repeat absorption interval was not working and told Victron about this. It works now.
My use is different on a leisure boat, when the boat is in use I want daily absorption, when it is in dock it only uses 5% per day. I have a 90% SOC threshold and 30 repeat absorption so in use it gets daily absorption but not in use then I get monthly absorption.
You need to set your values to suit, and based on my tests with daily repeat absorption, a high SOC threshold is better. The trouble I found with the repeat absorption interval set at 1 day is if absorption finishes at 14:00hrs then the next absorption starts at 14:00hrs the next day, not at dawn so the next day may not charge fully. An SOC threshold that is passed during the night always means absorption starts at dawn.
it always charges to full 54V, and 54V is full battery. 56V is just the drop on top that stresses the cells…
I also think this is the correct explanation.
This could also be acceptable. I could live with always 56, if its only stays there 3 minutes.
No sync today…
I wasn’t looking to this in the right way. tnx for forcing me to think on this. I guess I need to go shower to have a clearer image 
Because “charged voltage” was set at 55.6V sync will only happen every 30 days (Repeated Absorption interval) or if voltage reaches these 55.6V.
For the voltage to go that high, I need to trigger absorption.
If I want sync to happen daily (which I want), I need to reduce the “Repeated Absorption interval” to 1 or raise the “SoC threshold” to a value which I know it gets to every day, for example 80%.
The problem here remains. Sync to 100% is attached to absorption, and absorption is on a value I would prefer my batteries would not reach.
Victron must allow lower absorption voltage; I understand not allowing raise it, but lower it and not using full capacity, is my right!
I changed my settings for now to 80% and 3 days for 5 minutes.
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Reading the last few messages I realised how difficult it is to understand the terms Victron uses for describing what is widely know as end-of-charge detection. Why is it called ‘sync’? Why is the voltage being used called ‘charged voltage’? And why is there an SoC threshold for which the explanation speaks about initiating a ‘full cycle’? And, more fundamentally, why is there an implicit option to let charging terminate and not assume the battery be 100%? And why is that not simply an option: charge to X%, but instead a threshold?
Why would someone want a battery fully charged and not sync to 100%?
Similar things can be said of the absorption and balancing. Victrons’ NG batteries only do passive balancing at a certain cell voltage (like most do) and for that point to be reached, you need the voltage be what the battery says is must be: 56V. Why is there an option to lower it? There indeed (@zedamoca ) won’t be any balancing if you lower it.
Why would someone want a battery with unbalanced cells and not balance them but wait for it to become worse?
@zedamoca I believe you get one thing wrong: sync is not attached to absorption. I had it sync properly last two days using “charged voltage” set to 54.9V and “maximum charging voltage” set to 55V. That was the test I accidentally did. So you can use it at a lower capacity, though it would never balance.
See the short green peak in this image:
That last remark about never balancing might not be true or not. Last night I had Perplexity Pro go over all the documents to see if there is more information about how the NG balancing works. I really pressed it because I thought it was not accurate at some points. It was a long conversation, and it ended with the remark: " So, while the language in the manual is ambiguous, the documented operation and design are that of a passive balancing system." I looked up all the references, and indeed, that is an accurate remark about the state of affairs.
If you want to read the whole conversation (it is rather interesting) I can send the link.
yes, please send the link, I’m interested in reading more.
Where do you see “maximum charging voltage”?
From your screenshot
I believe we use the term “balanced” differently.
I consider a battery balanced at a certain voltage, when the current drops. This means that, at that voltage, if no cells are taking current, the cells are balanced at that voltage; no?
Victron uses this term only when it reaches 3.5v per cell and the current drops.
As many tests, done by many different people show, the benefit of putting more than 3.45V per cell is almost negligible. The higher the voltage the higher the stress.
2 views can be taken in this subject.
The view I prefer, which is “why put more stress in the cells if there is no big benefit” and there is Victron’s way which I believe it is “why not make it slightly higher? it can charge batteries faster on people with limited energy, and it adds only a small bit more stress bringing cells to 3.5V.”
I would prefer 3.45V, if I knew this limitation, I wouldn’t had bought these batteries.
It’s not a big thing, but annoys my autistic brain.
Now that it doesn’t stay there endless hours, it’s less bad. none the less…
Hmm, private messaging is not enabled on the forum and rather not share that link here in public.
Yes, 100%, no, 55V. I made sure the axis were on the image, but still not visible?
Balancing is about every cell being the more of less the same voltage/charge. It does not matter much which voltage, but the key is that they are all equal. Current drop is not a factor I think.
The 3.5V most likely is from the balancing circuits (think a zener diode and a resistor) in the battery: they only become active at 3.5V. Unless this circuit is more sophisticated, balancing cannot happen at lower voltages.
I assume that 3.5V is already at a save margin from over stressing the battery. I cannot tell of course, I must believe the manufacturer. But I can also not tell if margin is not enough, so I cannot understand your worries exactly.
you could send to my cat’s gmail, it’s
gatapinky at gmail
I’m an idiot, I was looking on other screenshot of you…
[quote=“hennephuis, post:57, topic:36747”]
I see it on the console gotcha.
3.5 is not bad. Its just that 3.45 is better.
3.5 is still safe, yes.