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Cell capacity at different temperatures
(08-23-2019, 12:09 PM)Overmind Wrote: @ajw22 in the case of Li-Ion that is not valid. Li-ion works great in low temperatures and it's a disaster at high temperatures.
This is valid for anything from smartphone batteries to 18650 cells.

I bed to differ. There have been many tests confirming that EV range drops significantly in cold weather, even when not using the heater. Ie usable capacity drops when batteries are cold. But the effect is less noticeable on slow discharge rates, such as phones.

And many EV makers are coming up with systems to pre-heat batteries to optimum temperatures before arriving at the charge station. Ie max charge/discharge rate drops when batteries are cold.

So while LiIon may not slow down in the cold as much other chemistries, it certainly performs much better when warm.
Modular PowerShelf using 3D printed packs.  60kWh and growing.
(08-25-2019, 10:00 PM)energysteven Wrote: Can you identify the cell manufacturer and part number? 
If so, please share that information since it seems you're committed to life-cycle testing these cells.
Also, could you include the charge time, the rest time, and the discharge time - in otherwords, what your cycle looks like?
And how often you cycle - how many times a day?
As to your question on how temperature affects cells, the "aging path" is affected by cell temperature, cell nominal or average state-of-charge, and cycling severity.
Even daily thermal cycling of the cell - similar to the "cold start" of an automobile on the driveway needing time to "warm up", affect cell aging.

They are LG cells and the packs they come from say 2000mah.
There is no set charge time, discharge time or rest time.
The cells are charged with a tp4056, and discharged with a ZB206 at 1A.
Its a manual process, so timing is "When I get to it".
Typically I will start one test in the morning and two more in the evening although this can vary a fair bit.
I believe I can fairy accurately predict that capacity will be 1950-2000mah when tested "cold" and 2000-2050mah when tested "warm"
I have slowed testing recently so am am only at 107 tests across the 2 cells now but I have been recording start temperature for a while.

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