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According to what I understand about cycles of deep cycle batteries is that a cycle is when a battery is drained to it's cut off voltage and then recharged to full capacity again.

I experienced something different and therefore my question:  Is my ICC calculating my Pylontech's cycles as episodes of use?   

After my Pylontech was applied the first time to carry us through the first load shedding happening (after installation of my system)  I noticed 1 cycle on the dashboard of ICC the moment after the Pylontech was fully charged again.  I was so exited about showing Escom a specific finger and was consistently in front of my installation and on my phone monitoring the performance of the brand new Pylontech US3000 on ICC.  At the end of load shedding it wasn't close to 46volts and not below 50% SOC as displayed by ICC - BUT 1 cycle was recorded.

I hoped to see somewhere a log of data to indicate to me that I missed the possibility that the Pylontech was in fact drained to the cut off voltage at least, but apparently there isn't such log available.  Sorry, if I'm wrong - but this is disappointing of the ICC monitoring application and let me to believe that ICC is calculating a cycle as a period/episode of usage of the Pylon battery.

Last night another load shedding experience and again the battery wasn't drained,  BUT ICC displayed, even while the battery was still charging, another cycle recorded (see attached image).  

So is ICC calculate a cycle as a period/episode when the battery was used (not drained) and recharged?    I lost 2 of the 6000 cycles of the Pylontech only because I made use of it twice - or do I have the understanding of a cycle completely wrong?

2cycles ICC.jpg

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2 hours ago, Cassie said:

Sorry, if I'm wrong - but this is disappointing of the ICC monitoring application and let me to believe that ICC is calculating a cycle as a period/episode of usage of the Pylon battery.

ICC is not calculating the Pylon cycle number - it is a number that it reads directly from the Pylon BMS.

I do not know what triggers the Pylon BMS to register 1 cycle (SOC, voltage, ...). Maybe anyone else here does?

2 hours ago, Cassie said:

I hoped to see somewhere a log of data to indicate to me that I missed the possibility that the Pylontech was in fact drained to the cut off voltage at least, but apparently there isn't such log available.  

You can see the last 12 hours of battery SOC, voltage, and current in/out-flow under the tab 'Graphs' and 'Battery trends'. There you can check down to what SOC and voltage your battery drops during loadshedding

2 hours ago, Cassie said:

So is ICC calculate a cycle as a period/episode when the battery was used (not drained) and recharged?    I lost 2 of the 6000 cycles of the Pylontech only because I made use of it twice - or do I have the understanding of a cycle completely wrong?

As a first thing I believe that you should never use the Pylon down to its cut-off voltage and have it shut down completely

I think it comes down to what you mean by 'drained' and 'used'. An example: If during a normal day I am running in SBU mode, my batteries have already been fully re-charged, and then I get a bit of cloud cover that my PV production drops below my load for a while - then my batteries will start being discharged. If the cloud cover hangs around for a bit longer, my batteries might even get discharged back down to 90%. Then the sun comes back out, my PV ramps up, and eventually fills the batteries back to 100%. To my understanding this will not be registered as a cycle by the Pylon BMS. But if I use my batteries during the night and (instead of using them down to just over 20% like I normally do), I set ICC to switch back to Utility already at 40% to keep a bit of reserves for unannounced loadshedding - then the Pylon registers this as a cycle

2 hours ago, Cassie said:

I lost 2 of the 6000 cycles of the Pylontech only because I made use of it twice

I personally would not be too worried about that. Remember that even a 1 cycle per day, the 6000 cycles lifetime than Pylontech claims equates to more than 16 years. In the grander scheme of things, I don't think that 2 cycles will make a difference 😉

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1 hour ago, wolfandy said:

As a first thing I believe that you should never use the Pylon down to its cut-off voltage and have it shut down completely

My definition of the cut off voltage is a voltage that is not near the "shut down completely" stage.  I'm talking about my experience with lead acid deep cycles for the last 5 - 6 years where I never dropped them below a total voltage of 47 - 48v.

What is the cut off voltage you are referring to on the Pylon.  And what is the voltage more or less at  20% and 40%.  This is what I don't understand, my pylon was never close to 46v and a cycle was registered?

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Posted (edited)

One cycle is a full charge & discharge of the rated battery capacity.

So, if you discharge it from 100% -> 50%, then recharge it from 50% to 100% it counts as half a cycle.  If you do this twice, you consume 1 cycle of battery life.  Discharging from 100% -> 20%, then recharging to 100% again counts a 0.8 cycle.  Quite simple, really 😀

If you have a Pylontech battery and it communicates to your ICC Pi with a comms cable, ICC simply reads the cycle count from the battery management software and does not calculate anything.  Oh, and it also has nothing to do with voltages or current either.

Edited by ChristoSnake
Added voltage/current bit...

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2 hours ago, Cassie said:

What is the cut off voltage you are referring to on the Pylon.

I always had 46V in mind - but just looking again at the manual I realized it is actually 45V is actually specified as lowest discharge voltage point

2 hours ago, Cassie said:

And what is the voltage more or less at  20% and 40%

I am not an expert on this, but to my understanding the SOC and voltage correlation is not linear. But I do not know even closely enough about lithium batteries and simply rely on the SOC that the BMS provides. Maybe just a screenshot of my Pylons from today as example:

Voltage.thumb.JPG.be695fe6ef7bf07beadb2af415120fed.JPG

57 minutes ago, ChristoSnake said:

Discharging from 100% -> 20%, then recharging to 100% again counts a 0.8 cycle.

Are you sure about that? I always thought that the BMS only counts in full cycles - but also have to admit that I've never paid that close attention. But I will keep on my cycle counter when I use my batteries down to 20% tonight and recharge them tomorrow

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33 minutes ago, wolfandy said:

Are you sure about that? I always thought that the BMS only counts in full cycles - but also have to admit that I've never paid that close attention. But I will keep on my cycle counter when I use my batteries down to 20% tonight and recharge them tomorrow

Yep - when you remove the battery's full capacity and then add it back again, it counts as a full cycle.  That means that 100x charge & discharge sessions of 1% each counts as a full cycle. Or 10x sessions of 10% charge/discharge each constitutes a full cycle.  You can mix it any way you want!

Voltage vs SoC changes depending on whether the battery is being charged or discharged, and has very little in common with the actual SoC.  Here's a graph of the two overlaid to give you an idea.

  • I charge mine to 52.5V, and they stay there once charged with the load running off solar.
  • When the sun sets and they take over the load, their voltage drops to about 49.7V even though they are still at 100%.
  • The voltage remains fairly constant until the SoC reaches 70%, after which they take another dip in voltage to 49.3V.
  • From there they drop gradually to around 48.9V in my system, which corresponds to a 40% SoC in the mornings.
  • Once solar takes over the voltage jumps to over 50V again as the charging starts.
  • You can also see the typical "Pylontech plateau" at 89% SoC while the BMS does its cell balancing before the voltage takes a sharp increase to 52.5V again.  Some folks say this only happens with new batteries.  Mine have 350 cycles on them and still do that.

The graphs will obviously differ depending one the amount of batteries you have and the load your put on them.  Fewer batteries means that each of them must supply a larger percentage of the total load, and therefore they'll take a bigger voltage knock.  More of them means they each have an easier life, meaning less of a voltage drop per battery.   No two systems will be exactly the same, but the principle stays the same...

image.thumb.png.855d19aa1d51cad3ecb8ce559f49b0a4.png

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16 minutes ago, ChristoSnake said:

Yep - when you remove the battery's full capacity and then add it back again, it counts as a full cycle.  That means that 100x charge & discharge sessions of 1% each counts as a full cycle. Or 10x sessions of 10% charge/discharge each constitutes a full cycle.  You can mix it any way you want!

Cool - thanks for the info. Learned something new again today 😀

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14 hours ago, ChristoSnake said:

Yep - when you remove the battery's full capacity and then add it back again, it counts as a full cycle.  That means that 100x charge & discharge sessions of 1% each counts as a full cycle. Or 10x sessions of 10% charge/discharge each constitutes a full cycle.  You can mix it any way you want!

Voltage vs SoC changes depending on whether the battery is being charged or discharged, and has very little in common with the actual SoC.  Here's a graph of the two overlaid to give you an idea.

  • I charge mine to 52.5V, and they stay there once charged with the load running off solar.
  • When the sun sets and they take over the load, their voltage drops to about 49.7V even though they are still at 100%.
  • The voltage remains fairly constant until the SoC reaches 70%, after which they take another dip in voltage to 49.3V.
  • From there they drop gradually to around 48.9V in my system, which corresponds to a 40% SoC in the mornings.
  • Once solar takes over the voltage jumps to over 50V again as the charging starts.
  • You can also see the typical "Pylontech plateau" at 89% SoC while the BMS does its cell balancing before the voltage takes a sharp increase to 52.5V again.  Some folks say this only happens with new batteries.  Mine have 350 cycles on them and still do that.

The graphs will obviously differ depending one the amount of batteries you have and the load your put on them.  Fewer batteries means that each of them must supply a larger percentage of the total load, and therefore they'll take a bigger voltage knock.  More of them means they each have an easier life, meaning less of a voltage drop per battery.   No two systems will be exactly the same, but the principle stays the same...

image.thumb.png.855d19aa1d51cad3ecb8ce559f49b0a4.png

Hi Christo,

Thanks for the info, very helpful.

Have you lost any battery capacity after 350 cycles?

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2 minutes ago, francois said:

Have you lost any battery capacity after 350 cycles?

Who knows these things?

Measurable things are that the Pylontech BMS dropped my battery pack's SoH from 99% to 98% when I hit 320 cycles, so I assume they will drop by another percentage point when I hit 480 cycles?  The BMS gradually keeps lowering their maximum capacity (in available Ah) as they age, so when fully charged ICC now reports that I have 102% of available capacity!  It seems mostly to affect the oldest battery, and I think this is pre-programmed behaviour from its BMS based on cycle count and may not reflect the actual performance of the pack in real life?

image.png.b2d3d92caf982ad3fee153d6cc69c4a2.png

I also moved the goalposts by adding additional batteries after starting off with just one at the beginning of last year, and the new ones have fewer cycles on them which affects the performance of the whole battery pack.  We've also optimised our power consumption at night by letting PCs go to standby much sooner, saving a large thermos flask with hot water for instead of boiling cold water each time, dropping the fish tank temperature by a degree or two, heating the house during the day and not at night during winter (we only use the gas fireplace at night), using electric blankets instead of heating the bedroom, etc.

Any way - we are now as close to off-grid as one can get when running in grid-tied mode 😀

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1 minute ago, ChristoSnake said:

Who knows these things?

Measurable things are that the Pylontech BMS dropped my battery pack's SoH from 99% to 98% when I hit 320 cycles, so I assume they will drop by another percentage point when I hit 480 cycles?  The BMS gradually keeps lowering their maximum capacity (in available Ah) as they age, so when fully charged ICC now reports that I have 102% of available capacity!  It seems mostly to affect the oldest battery, and I think this is pre-programmed behaviour from its BMS based on cycle count and may not reflect the actual performance of the pack in real life?

image.png.b2d3d92caf982ad3fee153d6cc69c4a2.png

I also moved the goalposts by adding additional batteries after starting off with just one at the beginning of last year, and the new ones have fewer cycles on them which affects the performance of the whole battery pack.  We've also optimised our power consumption at night by letting PCs go to standby much sooner, saving a large thermos flask with hot water for instead of boiling cold water each time, dropping the fish tank temperature by a degree or two, heating the house during the day and not at night during winter (we only use the gas fireplace at night), using electric blankets instead of heating the bedroom, etc.

Any way - we are now as close to off-grid as one can get when running in grid-tied mode 😀

Thanks Christo,

Good job on reducing the power usage.

I see you are also using a Infinisolar, I have the same but the baby 3kw version. 

 

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1 minute ago, ChristoSnake said:

Here's another view of the weirdness:

image.png.86131da1f8e0c445cadb17a8617008c4.png

Ah yes I get the same, my battery capacity is now 98.7 ah, and when they're fully charged ICC reports 101% SOC and 100AH, it does eventually come down a bit after they're left to settle.

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Wow!  This is so much knowledge one gets from the experience of other members.   This Litium technology is definitely a complete new discovery for me.  I get so jealous of younger guys, the future of technology development will be all part of their lives and not mine.  But I made it to Lithium technology and just curiously waiting for G5, and if the technology gurus hurry up I might experience a few more exiting developments.  

Designing and installing my own system, rewiring my main DB board to support my house via the inverters or grid but also separating the grid support part to feeds the geyser, (when there is no sun for the solar heaters) my workshop and the gate motors (with their own battery support) - and all your support with knowledge, enable me to keep the dementia away.

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