Full Charge/Discharge graphs for 4YO Winston LFP cell

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Full Charge/Discharge graphs for 4YO Winston LFP cell

Postby karrak » Mon May 08, 2017 11:28 pm

Finally got around to doing some full charge/discharge tests for the 90Ah cell that I took out of my friend's nearly four year old LFP battery.

On the graph I have set 100%SOC to 90Ah. It is an interesting coincidence that the cell has around 90Ah available capacity after four years. Unfortunately I don't have any baseline data to compare it to. I have heard that new cells usually have more than 100% capacity when new so it is more than likely that this cell has lost some capacity.


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
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Re: Full Charge/Discharge graphs for 4YO Winston LFP cell

Postby Warpspeed » Tue May 09, 2017 11:39 am

Very helpful.
Thank you !
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Re: Full Charge/Discharge graphs for 4YO Winston LFP cell

Postby offgridQLD » Thu May 11, 2017 7:35 am

Nice one thanks for going to the trouble of testing it.

Yes its be shown that often the Chinese cells had more that nominal capacity from new ( particularly the earlier Winston and Calb cells) It was a reasonable amount more to like 15% or so on some. Some of the real early Winston cells where way over nominal.

Though consistency in capacity from one cell to another wasn't that crash hot and there were some complaints about that on earlier cells from several brands.

If the advertising spill is to be believed more effort was put into capacity constancy (though automated manufacturing) in doing so the cells capacity was dialed back a little to closer to nominal (though still over) Reading some reports from businesses dealing with and doing in house tests of the Calb cells they did notice changes in the cells from the earlier blue cells to the grey CA cells that aligned with the advertising spill.
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