General > General Technical Chat
Don't keep fully charged Li-Ion in long term storage, they tend to bulge
tom66:
There's a reason Tesla, VW, Polestar, and MG all have a recommended 80% charging limit, with the 100% being reserved for road trips. If you keep an EV battery between 80% and 0% (there's little disadvantage to going to the low state of charge) then the battery will last a really long time.
Siwastaja:
--- Quote from: tom66 on January 15, 2023, 01:27:04 pm ---There's a reason Tesla, VW, Polestar, and MG all have a recommended 80% charging limit, with the 100% being reserved for road trips. If you keep an EV battery between 80% and 0% (there's little disadvantage to going to the low state of charge) then the battery will last a really long time.
--- End quote ---
According to my tests, it's the cycling damage which is pretty significant between 80% and 100%; especially at higher currents and lower temperatures. This is the region of lithium plating. Calendar fading component depends a lot on the cell, some are much better at 80%, some are not. But cycling damage component is always better when you stop at 80%, so that's a reason alone to do it.
This is also why I'm a little bit naysayer when it comes to this "boohoo, follow the manufacturer instructions and continuously cycle the cell between 100% and 80% instead of CC-CV float charging at 80%" stuff we occasionally discuss, and recommend floating at 4.0V instad.
BravoV:
--- Quote from: Siwastaja on January 15, 2023, 01:24:53 pm ---
--- Quote from: BravoV on January 15, 2023, 01:18:07 pm ---Alternative view, on storing Li-Ion cell, the sweet spot is 4.03 volt, the longer the cell is soaked in higher voltage, say like 4.15 volt, the faster the decay.
--- End quote ---
As always, "alternative views" tend to be wrong.
--- End quote ---
According to an "anonymous" source in some public forum, compared to Prof. Dahn, yeah, right. :-DD
Siwastaja:
--- Quote from: BravoV on January 15, 2023, 01:49:10 pm ---According to an "anonymous" source in some public forum, compared to Prof. Dahn, yeah, right. :-DD
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Read and try to understand what is said, instead of who is saying that. Usually there is no contradiction at all, you are just being confrontative for no reason. Only when there is contradiction, then you might want to apply "appeal to authority" - but be careful; see the "Nobel disease" phenomenon for example. For on-topic example about li-ion, John B. Goodenough, called the inventor of lithium ion, have caused embarrassed reactions within the industry in his old days.
With appeal to authority, you sometimes win the internet argument, but you can't win the understanding to the subject that way.
In this particular case, Prof. Dahn is apparently (I did not check) saying a li-ion cell used by Tesla shows significant calendar fading improvement when stored at 4.0V, and engineer A. Alhonen (me) says that during his testing, Samsung ICR18650-26H did show significant improvement at 4.0V, but the newer Samsung INR18650-29E did not. There is absolutely no contradiction as I see it.
RoGeorge:
--- Quote from: magic on January 15, 2023, 12:03:01 pm ---Is there any "quick and dirty" way to put a battery into a reasonably safe long term storage level without coulomb counting?
Like, say, (dis)charge to 3.6V or 3.8V or something of that sort.
--- End quote ---
That's what I come with, because I have plenty of DZ4V3 (NOS), and power LEDs with radiator (from bad light bulbs :D):
Either charges or discharges until the battery reaches 3.7V, the Li-Ion cell is ready for long term storage when the two LEDs light at about the same intensity. Main goal was to keep the currents small enough so any small battery can take that (50mA when charging, 20mA when discharging).
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