Making a case for Victron to consider the new "Pylon Feature" for all

IOT (The internet of things) GX Devices
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“Pylon feature” (my nickname):

I know there are strong views for and against some of my suggestions, but all views aside, what is the new issue one has to look out for on Lithium, for this post, Lifepo4 batteries?

BMS job is to protect a Lifepo4 bank.
Remember, with lead acid some bought Victron / other make balancers to help.

These protections include:

  1. A cell shall not exceed 3.65v.
  2. BMS has a balancer built in facilitate point 1.

What are the challenges: (I was introduce to this issue when LBSA was brand new selling DIY banks and BMS’es)

  1. BMS switching off to protect can be dramatic for the equipment. Victron can get a DC Ripple.
  2. Parallel banks will mitigate this. Fact. But not all have parallel banks, the wider consideration.
  3. Long term, the “more connections” consideration coupled with more cells installed = more points of failure.

I’m not against parallel banks at all!!! It is/has a clear benefit.
I focus more on the fact that cells can become an issue based on my personal experienced and in the last year or so, more feedback from installers generally ito the amount of warranties being honored, alluding to the cells as the next level consideration. Note: Lead acid banks had same challenges. But the cells where inside the 6v/12v battery.

The Points I consider: (In non-engineering terms)

  1. I’ve been told by experts here, Victron vids / documentation if memory serves, that the fewer connections on the DC side, the better.
    Extrapolating that solid advice:
  • My personal preference advocating fewer larger cells = fewer points of failure.
  • More scope, I believe, for cells to last longer i.e. more “fat” in a 280ah cells than a 105ah cell pushed to the limit.
  1. We also now know that if cells are:
  • not Grade A Batch Matched, the best cells in other words,
  • wear and tear or manufacturers defect,
  • in due course, just plain old age,
    That it will contribute to the problem of a BMS forced to switch off due to the volts shooting out, the balancer not being able to keep it in check, causing a potential DC Ripple on a single bank.

Lifepo4 banks, we now have control on cell level, a huge benefit for us.

Far as I know:
A DC Ripple is predominantly a Victron design matter, being a LF design (which has benefits we like), that HF inverters won’t necessarily have the same risk I was told by experts.

As a matter of fact, Victron has a document out on DC Ripple explanation and rectification.

I therefor make the case for Victron to consider, going forward, once tested, to make the “Pylon feature” a user setting as a standard option.

I.e. if a cell hits x-volts (user decides or manufacturer):

  • reduce the charge amps immediately by Y amps on a incremental sliding scale. (Clever developers can figure out the finer details.)
  • Send a clear warning to the user that a issue has occurred.

Been a “lone voice in the dark” (it felt at times) advocating this matter. Then the Pylon Feature saw the light. It is a “thing”. :slight_smile:

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Thanks TTT. I am all for this. The more protection the better.

Is this something that could be done merely by programming/adding it to Victron software?

Or will it be battery dependent with different code for most makes and model batteries? Asking as layman here because I understand it took considerable effort by Victron to do this for the Pylons.

So the groundwork has been done. Some slight changes to it may be necessary I suspect depending on the battery’s specs?

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Yes, it is all programming.

On the condition, on like DIY banks, the Venus/Cerbo must be able to see the individual cell volts.

Because, my opinion, it must be at the source of the control, being a Cerbo/Venus.

Like i.e. a JK BMS (I’m told) is seen by the Venus/Cerbo. Just check.
Where the BMS is not “seen”, no driver yet, then using @Louisvdw driver comes to mind.

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Alright! Now why did I not understand this earlier? I probably skim-read it too fast. Well, yes, that is still true. But I think you need a balance. It’s the age old pros and cons thing. One string… less to go wrong, but if something goes wrong, it is the whole thing that goes wrong. Two strings, two things that can go wrong, but the odds of both going wrong at the same time is lower.

I would take three 100Ah strings over one 260Ah string. But I would also take 3 x 200Ah strings over 6 x 100Ah strings. There is a balance to be had.

As another data point, the BMW i3 EV? It has one 400V 60Ah string. Teslas batteries on the other hand have multiple strings (6s74p). You can lose a cell, and still keep most of the capacity.

Regarding the Pylontech issue: It really is unclear why they go out of balance. There would be two cases. The one case, is that there is an actual issue with a cell going bad. The other, is that the cells are fine, but they somehow become unbalanced.

Now, there is no reason for a battery that is consistently charged to 3.5V per cell, and that was balanced to begin with, to get out of balance. No reason. And once it starts to go out, there is also no reason why this new “feature” will fix it.

All this new feature does, is avoid high voltage alarms. In a way, perhaps, it also helps to keep the module connected for longer periods of time (because obviously, when it disconnects on high voltage, it cannot really balance), but there is no reason that a battery with a high cell, which connects and disconnects repeatedly from the bank, will not eventually balance itself given enough time.

But, maybe this is all it takes then. And another tick mark for why proper voltage control really is non-negotiable.

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image

Here I’ve done the hard part for you, now all you need to do is fill in the Python code :rofl:

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Just a note here. The driver is now maintained by Manuel Delmonego.

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In my experience it has always been the former. 14 of the 15 cells are all at the same voltage, except for the one cell that shoots out every day. You can wait for the balancer to get that cell back into perfect balance, but if you discharge the battery then the next time it recharges close to 100% that same cell will shoot out again.

Every time this has happened I sent the logs to Pylontech and they offered to replace the battery without even suggesting anything I should try first. This tells me it has to be an unrecoverable issue with the cell, since I cannot imagine it would make business sense to replace batteries if there is any chance of recovery.

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Here are some of the cells we imported. Grade A Batch Matched.

Note the subtle difference in this batch.

image
image1481×485 21.8 KB

I manually grouped the cells in batches. Did not send out a 292.5ah cell with 289.3ah. Very basic simple attempt my side.

Now I would imagine brand names do the same. Just on a much larger scale, relying extensively on quality control, with a acceptable margin of error.

Hence I can understand when thousands of banks are sold, country specific, will have issues, develop issues over time.

And why I feel comfortable to rather focus on one bank cells, control that, than worrying about more parallel banks, at times even newer cells.

Subtle cell level difference, and time, is what I deduced the key to a bank staying in balance longer.

Not to mention any manufacturers acceptable losses ito their quality control.

On top of that, the older the cells get, being cycle driven, it being a chemical reaction, the more balancing will be required over time.

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I have a question. I see 220ah max charge current.

Example:
Say each bank is max 50a the BMS will allow.
4 in parallel = 200a max charge current.

My question: (and this is the shiite I ponder on, my luck it happens to me)
What happens when one, or more BMS, at full charge amps, “duck out” under load, i.e. disconnecting as their individual 50a is exceeded?

Will the remaining batts handle that?

Genuine question.

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Did you change the title? Anyway, my answer to that is this: Ask the dbus-serialbattery maintainer to do it. That’s where it should be.

Edit: To be clear, we have an Afrikaans saying that translates roughly to “Don’t make your problems mine”. And that’s why I’m hesitant to make this a global feature. The BMS should manage the battery. Exceptions are made at times, but once you take this too far, it just becomes the way.

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Now if we were Mandalorian… :wink:

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After reading all of the above - this is the answer! If you have a BMS - “just disconnecting” - then this is a BMS issue.

Root cause argument wins for me…

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I mean, of course one wants to be as nice as possible, but there is also the matter of shifting responsibility. Every software team in the world would much rather that someone else fixes it. We have enough to do already :slight_smile:

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Take Note:
I’m not bound by any warranty.
Can add a bigger balancer any day,
Can upgrade to a newer better state-of-the-art latest clever software BMS any day.
Can replace a cell if I want.

My “horse in this race” is for the wider audience, the installers having to deal with clients.

If I may.

BMS is a last-in-line safety control to protect cells by disconnecting.

The “root cause” of the protection trigger, is cell/s shooting out (for whatever cause) due to the charge amps at that moment in time.

Therefor, intelligence at the source, take the information from the BMS, like the cell volts, and help the BMS balance better/faster, balancers that operate with mA, not amps, to avert forcing the BMS to protect and disconnect, all because the source is unaware of any brewing problem.

How can a BMS reduce the charging amps?
Crudely by opening the charge relay. A last ditch attempt to protect the bank against the core software of the system, where the intelligence sits, doing what it supposed to do i.e. charge the batts.

I’m open to be educated on this. Where I have it wrong.

The wider audience:
As has been alluded to in another thread, replacing under warranty, not a long term solution for any manufacturer, be that battery or hardware.

Open minds are what is needed.

Not to forget:
Once a replacement has happened under warranty, if it happens again, it becomes a costly exercise for the owner, who bought off-the-shelf, properly installed equipment.

It becomes the installers problem too …

Be a leader:
Those thousand of cycles Lifepo4’s can allegedly achieve, what can be done more to ensure it happens, should be the focus of manufacturers, in my opinion.

More intelligence is required … the parts are in place.

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No.

I think this is a decision for Victron highest levels to consider, make, not the “dbus-serialbattery maintainer”. But their insights into the matter, invaluable. :slight_smile:

Request should also come via approved installers channels, having been asked for by their clients who start to understand better.

Done properly in other words.

Will it take time, without a doubt.
The seed must come from somewhere.

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Agree and therefore the “first ditch”, etc, etc attempt should be managing things better… Even if the BMS manufacturer needs to add a ditch or 2.

The connected devices, etc should not and can not be expected (to some degree) to solve a major BMS/Cell failure on the Battery Bank Side.

My 2c.

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Have look at this video, re. the balancing issue on daily cycled solar systems.

I agree with Will, hence also the advice at times to keep a problem bank for ±7 days at 100% for the balancers to attempt to fix the imbalance after a while of use … to happen again, until a bank replacement is required.

Hence this thread, the BMS does need some more help from the charging source, due to the daily cycling.

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Titbit:
I’ve done the Zero BMS SOC. Let the system run till the inverter cuts out, as I agree with him. Use the damn batts.

The only reason I don’t run 100% SOC at 3.65v … 18 cells x 3.65v = 65.7v … damn no bro, that is me looking for drama, Victron is max 66v … and I do not do drama anymore.
Playing it safer because of 18 cells

When I have to remove cells later in the banks life, I will go “flat out”. My cells are not going to die of old age on me, like the Trojan Bank way back did.

The balancing, due to daily cycling, that is and still remains an issue though.

Remember, I’ll just upgrade my BMS, for I agree with his other vid, BMS will probably fail before the cells will. Also on my next build, will make the BMS easier replaceable.

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Quick question for you: How do you see all the brand name banks out there today getting a new BMS’es that has that “ditch or 2” added?

Is that even remotely possible?

Problem is compounded in that it will take a while for the manufacturers to effect that to be a standard feature going forward.

What does one do today?

Let me think … o wait, I know!!!

How about we ask a open minded equipment manufacturer to consider if they could attempt to facilitate the problem, we are all facing today, and for a while into the future. :grinning:

Had to throw some humor in.

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@mmaritz let me share with you another point I have pondered on.

Lets say I had brand name banks, in parallel.
Professionally installed.
10 years / 6000 cycle warranty.

Couple of years in, the one bank goes. Cell imbalance (probably what Will is on about.)
No problem. Replaced under warranty and installer gets it back in and balanced.
Then soon after, the 2nd bank goes.

Now I sit, not even say 5 years in with 2 banks that never lasted 10 years/6000 cycles with the same range, maybe slightly upgraded BMS, but with no “ditch or 2” added yet.

Can you imagine that horror show?

… another reason I went DIY, btw.

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