Hi there again can someone post a graphic of Voc vs Soc of a Winston cell?
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Voc vs SOC winston cell
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I haven't come across any official graphs of Voc vs SOC for Winston Cells.
I have graphed SOC v Cell Voltage from two sources. The data for the blue line comes from here http://advrider.com/index.php?thread...#post-18206897 and the data for the yellow line comes from some tests I have performed recently.
My tests involved setting Bulk=Absorb=Float to the same voltage at the start of the day and taking an SOC reading when the charge current had dropped to around zero.
SOCvVoltage.jpg
Simon
Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger https://github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controllerOff-Grid LFP(LiFePO4) system since April 2013 -
What about the SOC vs under voltage vs C discharge ? Is there a graphic showing what would be the SOC based on the voltage vs C????
Thx in advanceComment
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There is no good answer to your questions. Winston does not publish discharge rates. It would be too embarrassing if they did. Of the Chi-Com lithium batteries, Winston scores next to last place. Last place belongs to GBS. Winston and BGS Internal Resistance are very high is very high for the Chi-Coms. That means Voltage Sag under load will be much higher than expected. That is why Winston and GBS will not publish discharge curves.
What you want to do is set your Low Voltage Disconnect to 3.0 vpc. So if you have a 24 volt or 8S system, disconnect at 24 volts or if any cell sags to 3.0 volts. Limit charge voltage to 3.45 vpc and you are good to go.MSEE, PEComment
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Sunking's right.
Barba, voltage is a poor indicator of SOC, especially under load. However, stopping at 3.0v per cell is *roughly* 5% SOC. You may want to stop a bit higher at 3.1 to 3.15v per cell *rested*, which is roughly 20% SOC.
In-between values higher than this are hard to predict with any accuracy under load, and most attempt to do coulomb-counting or other current-measuring techniques to predict SOC under load. Even that is not totally precise, but good enough for ballpark figures.
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Originally posted by Barba View PostSunking please answer my specific question.
Is your answer going to be yes or no?MSEE, PEComment
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Originally posted by Sunking View PostWinston does not publish discharge rates. It would be too embarrassing if they did. Of the Chi-Com lithium batteries, Winston scores next to last place. Last place belongs to GBS. Winston and BGS Internal Resistance are very high is very high for the Chi-Coms. That means Voltage Sag under load will be much higher than expected. That is why Winston and GBS will not publish discharge curves.
Off-Grid LFP(LiFePO4) system since April 2013Comment
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Thx karrak for the info that is exactly what I was looking for. Personally I don't understand why sunking is so negative about Winston... My previous pack cycled thousands of times more than 500 cycles at 80% DOD and more than 15000 cycles with more than 5% DOD and still today after 6 years the pack has the same capacity as new. I always cycled at 0,5C but I am about to go as far as 2C for few minutes a day as my power demand as increased due to new toys in the house.
Now playing with 100 kW instant power......
Little scared to go there but I have no choice....
Thx again to everybody for the interest in this postComment
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Originally posted by Barba View PostThx karrak for the info that is exactly what I was looking for. Personally I don't understand why sunking is so negative about Winston...Last edited by Sunking; 04-03-2016, 09:50 AM.MSEE, PEComment
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Originally posted by Sunking View PostBecause they are failed Thundersky with the same poor performance.
If you look at the Voc graph and know what you are looking at, you can see how poor the performance is.
From the graph you choose 3.0 vpc disconnect.
Simon
Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger https://github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller
Off-Grid LFP(LiFePO4) system since April 2013Comment
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Originally posted by karrak View PostPlease tell me how I can tell how poor the performance is by looking at the Voc (Battery open circuit voltage). That doesn't give any idea what the battery impedance is and how the battery will work under load.
You could care less what the impedance is, it is internal resistance that counts, and it is right on the graph if you know what you are looking at. You do not have a clue what you are looking at. Give you a hint: Delta Voltage and Delta Current.MSEE, PEComment
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