Voc vs SOC winston cell

[PNjunction]

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.

[Sunking]

How do u know? Did u use them?

In the biz. Try finding a discharge curve for them You cannot do it or else you would not be here.

[Barba]

How do u know? Did u use them?

[Sunking]

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.

[Barba]

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 advance

[karrak]

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 controller

[Barba]

Hi there again can someone post a graphic of Voc vs Soc of a Winston cell?