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AndewJ

please help. Infinisolar + Pylontech batteries

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Hi, 

 

Can someone please help me with the recommended settings for 3 Pylontech batteries on a Infinisolar 4KW inverter? 

I have 16x 325W Solar Panels. The settings below don't seem to work well as it runs for 5 minutes and then switch off. The lights on the batteries are all lit up when I press the red button. 

There's a Raspberry Pi with ICC and the Pylontech cable as well. I was told that I need to change the settings in SolarPower and not ICC. Eskom is used at night. 

P1.png

P2.png

Edited by AndewJ

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1 minute ago, langou said:

Call number on website. They'll get you in contact with Johan.

I did and was told to email him. So is he the only one who can help?

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6 hours ago, AndewJ said:

Can someone please help

Hi Andrew, Johan is handling the front-line support. 

One thing i do see in your settings is that you allow for batteries to be discharged when no pv is unavailable, yet you allow AC to charge it right back up.  That doesn't look right to me. 

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8 minutes ago, Jaco de Jongh said:

Hi Andrew, Johan is handling the front-line support. 

One thing i do see in your settings is that you allow for batteries to be discharged when no pv is unavailable, yet you allow AC to charge it right back up.  That doesn't look right to me. 

I want to use Eskom at night and only use batteries when necessary. I understand that is what this setting is for. Or how else should I set it?

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26 minutes ago, AndewJ said:

Or how else should I set it?

Change "Load Supply Source (PV is Unavailable)" to Grid First and Battery Second. 

That should untick the "Allow battery to discharge when PV is unavailable" on the right side of the page. 

If you only want the PV to charge your Bats, you can select"PV only" in the "Charging source" drop down.  

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1 hour ago, Jaco de Jongh said:

Change "Load Supply Source (PV is Unavailable)" to Grid First and Battery Second. 

That should untick the "Allow battery to discharge when PV is unavailable" on the right side of the page. 

If you only want the PV to charge your Bats, you can select"PV only" in the "Charging source" drop down.  

Thank you. 

What do you think about the voltage settings ?

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4 hours ago, AndewJ said:

What do you think about the voltage settings ?

I would definitely reduce the float voltage setting. I would say 50.3 V, but others seem to suggest much higher. Perhaps they will be willing to say why they prefer such high float voltages. Maybe it's just a temporary thing until the cells are balanced, and modules balanced with other modules.

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10 hours ago, Coulomb said:

I would definitely reduce the float voltage setting. I would say 50.3 V

I wonder if this is really such a big issue with LFP. For one, I've never seen a can-bus battery actually lower the voltage unless there was something wrong (a high cell), so in most "smart" systems that follow the battery's parameters it will simply hold it at 53.2V permanently. It is however true that you slightly extend the life of the battery by not holding it at 100% all the time. To this end I've received a recommendation for 52V, because it is high enough for the balancers to operate, and it sacrifices only around 3% SoC at the top.

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3 hours ago, plonkster said:

52V, because it is high enough for the balancers to operate

But that would mean that the balancers are working all day. Where does the idea come from that the balancers have to work all day? Surely a half hour every day during the absorb stage is enough?

Sure, when first installed, or after a major change like a replacement of a cell or module, but otherwise, LiFePO₄ stays in balance with just a minor nudge as long as it's nearly every day. At least, that's my experience.

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59 minutes ago, Coulomb said:

But that would mean that the balancers are working all day. Where does the idea come from that the balancers have to work all day? Surely a half hour every day during the absorb stage is enough?

WEeeellll, yes and no. The balancers only activate if there is an imbalance. So they could potentially run all day if there was a reason to... but if there is a reason -- which as you say should be a rare event -- I would prefer that they run rather than not.

On the Victron batteries there is a float setting, eg on a 48V system we charge to 56.8V and then float at 54V, that would be 53.2V (bang on) and 50.6V for a 15s setup. So it's probably okay either way.

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21 hours ago, plonkster said:

The balancers only activate if there is an imbalance.

Duh, yes, my bad. I worded that terribly. If you keep the charge voltage high, it will *potentially* balance all day, and that's a good thing, but the battery voltage will also be very close to where bad things happen, albeit slowly, and that's a bad thing. [ Edit: but I forgot that simple bypassing stops working at high battery voltage, as Weber explains in the next several posts. ]

The Victron figures of 56.8 and 54.0 V (for 16S) sound suspiciously like lead acid values (14.2 V per six-cell nominal module, and 13.5 V respectively). But 50.6 for 15S sounds much more sensible to me.

Edited by Coulomb

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One other thing to consider here: If balancing is done in the usual simple manner where a resistor is switched across any cell that goes past the "bypass" threshold, say 3.45 V, then not only does no balancing occur when all cells are below that threshold, neither does any balancing occur when all cells are above that threshold, because all are bypassing essentially the same current. So holding at 53.2 V all day could just result in 14 cells sitting at 3.54 V and 1 cell at 3.64 V, or at the other extreme: 1 cell sitting at 3.46 V and 14 cells at 3.55 V, with no significant balancing occurring. With this balancing method, all the balancing happens in two periods: 1. in bulk stage on final approach to absorb, and 2. in float stage just after leaving absorb, but only if the float voltage (average per cell) is below the bypass threshold. So if we want to maximise balancing, then we need to maximise the time spent with the battery voltage hovering around the bypass threshold times the number of cells.

Of course Pylontech may use a different balancing algorithm, in which case all this may be irrelevant.

Edited by weber

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Sorry @AndewJ. I think there are two independent questions being discussed in this thread. One is the question of what the float voltage should be set to for Pylontechs. I think we so far agree it should not be lower than 50.3 V and it should not be higher than the absorb voltage setting (presently 53.2 V). BTW, "absorb" voltage is a correct term for what Voltronic confusingly call "bulk" or "C.V." voltage. But let's leave that for now. I'd like to read @plonkster's thoughts on my post above, on that question. I'd also like to hear from @PurePower and @Chris Hobson as to what they have settled on since I recommended a float voltage of 50.3 V to 50.7 V to them many months ago. Maybe that didn't work out for some reason.

The other (I believe unrelated) question is how to solve your original problem which, correct me if I'm wrong, is that the battery disconnects itself when it is nearing full charge. @Chris Hobson had that problem when his Pylontech battery was new (but with an Axpert running our LFP patched firmware, not an Infinisolar). At the time, I hypothesised that due to having been in storage for some time, the cells had drifted out of balance with each other (due to different rates of self-discharge), and one cell was going high voltage well before the others, and so the BMS was rightly disconnecting the battery to protect that cell. I suggested it would all come good by itself after a few days, as the BMS balanced the cells near the top of every charge cycle. But to avoid the nuisance in the meantime, he could temporarily lower his absorb voltage to the highest setting that would not cause the battery to disconnect. I suggested he try a "binary search", first dropping down from 53.2 V to 51.6 V and repeatedly splitting the difference. And I suggested that every day, he should be able to raise that absorb voltage a little until eventually he would get back to 53.2 V without disconnection, because the cells would all be balanced. I believe that worked, but he can correct me if I'm wrong.

I think the float voltage setting doesn't matter for this procedure, provided it is not less than 50.3 V and not greater than whatever the absorb voltage is set to at the time.

Edited by weber

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9 hours ago, Coulomb said:

The Victron figures of 56.8 and 54.0 V (for 16S) sound suspiciously like lead acid values (14.2 V per six-cell nominal module, and 13.5 V respectively). But 50.6 for 15S sounds much more sensible to me.

Default Lead Acid values in veconfigure is 14.5V for absorb and 13.8V for float. Depending on your battery construction you may drop float to 13.5 or push absorb up to 14.8.

Default LFP values is 14.2V for absorb and 13.5V for float. Again, you should adjust that according to the specifications of the battery you install, and if the battery has a smart CAN-bus BMS then none of that matters anyway as the BMS rules the roost.

I feel a bit cautious to say this, because the info came to me from someone at Pylontech but I am concerned that it was a bit hand-wave in the middle of another discussion, so use this info with that proviso, but the advise was to float at least at 51.8V because that is high enough for the balancers to work. When running ESS with DVCC on a Victron setup, 52V is used (for now, no reason other than that it is a nice round number and it does not sacrifice too much capacity at the top).

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4 hours ago, weber said:

because all are bypassing essentially the same current.

Victron batteries (for example, as you say this is the "usual way") use the resistor method, what I refer to as "passive balancing" where you simply bleed off energy at the top to allow the low cells to catch up. The switches are interleaved though, not sure about the details exactly, but they cannot all be on at the same time. The lowest cell will be pulled up, albeit quite slowly.

(For reference, the other kind of balancing, active balancing, actually transfers energy from a high cell to a low one. Much more efficient, but also a lot more complex and costs more).

My gut feeling is to stay clear from what I sometimes call the "elbow" voltage, that point when an LFP cell is so highly charged that it can rise steeply if you put as little as 100mA into it for as little 5 seconds... and that indeed means spending more time below 3.5V per cell... or around 51.8V :-)

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On the float voltage question, Pylontech correctly state that lithium ion batteries do not require a float stage. And it seems that some have interpreted that to mean you should set the float voltage the same as the absorb voltage. But what we mean when we say lithium ion does not require a float stage, is that when you reach the end of the absorb stage (as determined by the charge current having fallen below the "tail current" threshold while still maintaining the absorb voltage) you should just stop charging. So the float stage is replaced by an off stage. Charging then remains off until the battery voltage or the state of charge has fallen below some threshold that returns it to the bulk stage which is followed by absorb and then off as the cycle repeats.

But there is no way to have an off stage with the Voltronic inverters. Pylontech don't seem to understand that. When asked directly by email some months ago, what the float voltage setting for the Axperts should be, Pylontech's reply was "Hi, For Lithium-ion battery the float charge is not necessary. So just set to 48V as normal is enough." [sic].

In fact, the best approximation of an off stage is to set the float voltage to whatever voltage the fully charged battery would naturally settle to if it was rested for many hours without being charged or discharged. That's where the figure of 50.3 V to 50.7 V comes from (15 cells at 3.35 to 3.38 V per cell).

http://www-personal.umich.edu/~hpeng/DSCC2013_Weng.pdf
See figure 2 on page 3.

http://www.cse.anl.gov/us-china-worksho ... %20BMS.pdf
See the graph on the left of page 15.

Edited by weber

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44 minutes ago, weber said:

In fact, the best approximation of an off stage is to set the float voltage to whatever voltage the fully charged battery would naturally settle to if it was rested for many hours without being charged or discharged. That's where the figure of 50.3 V to 50.7 V comes from (15 cells at 3.35 to 3.38 V per cell).

Next year once the family are at school I can disconnect one Pylontech and see what voltage it settles to and we can end this debate.

1 hour ago, weber said:

I'd also like to hear from @PurePower and @Chris Hobson as to what they have settled on since I recommended a float voltage of 50.3 V to 50.7 V to them many months ago. Maybe that didn't work out for some reason.

I ended up with quite a high float voltage of 52.8V. My situation is a bit different to most in that I have a constant 1500W load from 9:30 to 14:30 and we generally only hit 100% SOC some time after 15:00. I am at float voltage for about 1 hour and then the PV tails off and so does the voltage. I added 2 extra Pylontech modules and they were not in balance so I spent more time above 3.5V per cell and they now beautifully in tune with each other. I have now lowered the float voltage and will check again after Xmas that they are still in balance.

1 hour ago, weber said:

The other (I believe unrelated) question is how to solve your original problem which, correct me if I'm wrong, is that the battery disconnects itself when it is nearing full charge. @Chris Hobson had that problem when his Pylontech battery was new (but with an Axpert running our LFP patched firmware, not an Infinisolar). At the time, I hypothesised that due to having been in storage for some time, the cells had drifted out of balance with each other (due to different rates of self-discharge), and one cell was going high voltage well before the others, and so the BMS was rightly disconnecting the battery to protect that cell. I suggested it would all come good by itself after a few days, as the BMS balanced the cells near the top of every charge cycle. But to avoid the nuisance in the meantime, he could temporarily lower his absorb voltage to the highest setting that would not cause the battery to disconnect. I suggested he try a "binary search", first dropping down by from 53.2 V to 51.6 V and repeatedly splitting the difference. And I suggested that every day, he should be able to raise that absorb voltage a little until eventually he would get back to 53.2 V without disconnection, because the cells would all be balanced. I believe that worked, but he can correct me if I'm wrong.

Hi @weber your recommendation was 100% we slowly got the cells in balance over a period of time.

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Contact Heinz at Full Circle Solar.

He did my setup and I am 100% satisfied. It is in operation since Feb without hassles.

My 4 Pylontech batteries charge to 52v and then float charge at 1amp keeping to 52v. There must be some advantage by charging the batteries at a constant amperage every time when power is restored after a shutdown of some sorts ( use it as a backup system without solar panels). I never open the box to check on the batteries.

I have never drained the batteries to the point where the bms would shut it down. And we had our share of load shedding in Witbank - Eskom or otherwise lol.

My objective was to have a system that would run without human intervention.

So far so good....

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49 minutes ago, Chris Hobson said:

Next year once the family are at school I can disconnect one Pylontech and see what voltage it settles to and we can end this debate.

No need Chris. PurePower already did it. He didn't say how long he waited, but he wrote (in a PM): "So, the voltage sort of stabilized around 50.8v as the loss in voltage slowed down drastically at that point." It has also been done more scientifically here, for individual LFP cells:

http://www.bestgopower.com/technology/documents/temperature-test.html

So that's well known, and the debate doesn't really depend on it. It's more about whether there might be a reason to float higher than the neutral 100% voltage, for example to make it able to balance for longer. That's why I wanted to be sure that plonkster understood that the requirement for balancing (using the fixed-threshold switched-resistor method) is not that the battery voltage must be higher than the balance threshold times the number of cells. But rather that it must be close to that voltage, which seems very likely to be 3.45 V x 15 = 51.75 V. Being close below it is just as good as being close above it, and ability-to-balance falls off equally as you go above that voltage as well as below it. So spending hours at 53.2 V is no more useful for balancing than spending hours at 50.3 V.

Edited by weber

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