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| Battery overcharing |
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| Andy Chee:
--- Quote from: Siwastaja on December 26, 2023, 11:25:12 am ---Normally, holding the cell voltage near 100% voltage is still something that a battery can take for years. --- End quote --- Does Tesla still recommend charge termination at 80%? I don't own a Tesla or any EV, so I don't know how charge management differs from mobile phones & laptops (if any). |
| tooki:
I think the problem is this: confounding two related, but distinct, things. One thing is “leaving plugged in”. The other is “storing at 100% SoC”. Lithium ion batteries do not like long-term storage at 100% SoC. Self-discharge and current draw from the device will lower the SoC, so the only way to maintain a 100% SoC is to regularly top it up. Many phones (though more and more are doing it differently) will do this if left plugged in. I once replaced the degraded battery in an iPhone 6 (my obsolete backup phone) with a new battery (replaced at an Apple Store, so zero chance of counterfeit battery) and after a year of being left plugged in, the battery swelled. But I say that leaving plugged in is separate because it’s also possible to be plugged in permanently but not strive for 100% SoC, which is exactly what newer iPhones and countless other devices (phones, laptops, etc) do: they let you set a different SoC target, and/or use intelligence to modify the charging strategy themselves. (iPhones now, by default, learn your usage habits and charge up to 80% only when you go to bed, and then top up to 100% just before you wake up.) Thus, saying that a device shouldn’t be left plugged in all the time isn’t really correct advice, either. What is categorically untrue is that leaving a device plugged in means it’s charging 24/7: doing that to a LiIon cell would kill it very quickly, be it with or without unscheduled rapid disassembly. Every LiIon charger chip uses proper CC/CV charging with defined termination voltage and current — in some configurable on the fly (e.g. via I2C), in others via config jumpers or resistors, and in others preset at the semiconductor factory. Only death-trap garbage from aliexpress ever uses “dumb” charging on LiIon, like the lantern bigclive found that used a capacitive dropper (!) to put unregulated DC directly onto the lithium cells and USB ports (including exposed metal)… |
| Siwastaja:
--- Quote from: IanB on December 26, 2023, 11:50:08 am --- --- Quote from: Siwastaja on December 26, 2023, 11:25:12 am ---You can disagree, but you are wrong, because facts do not care about agreement. --- End quote --- You have the theory about lithium ion cell chemistry, I have a fact about a dead battery. --- End quote --- Death of which was very unlikely caused by the normal use you described. But keep believing. |
| Siwastaja:
--- Quote from: tooki on December 26, 2023, 01:00:45 pm ---Lithium ion batteries do not like long-term storage at 100% --- End quote --- Yeah, true. But remember the two-fold relativity of this: first, it might be a good compromise. Battery stored at 100% might still last longer than the desired lifetime of the device, especially if charge rates are small, temperature is never very high, and cells are of good quality (e.g. Panasonic and Sony cells I tested performed very well when stored at full charge). Another relatively interesting feature is that storage at, say, 80-90% might not increase the life expectancy at all, it depends on the small details of cell chemistry; I have seen data where a cell stored at 80% loses capacity faster than at 100%, although my own measurements show a small improvement on nearly every specimen. The large and reliable improvements, however, only start significantly below 80%. Note this calendar fading is different from cycling damage: by limiting maximum SoC to 80%, cycling damage done on each cycle is significantly reduced. |
| electronium:
According to my experience in the field of batteries, lithium batteries should not be overcharged and the battery will blow up, which is dangerous. As soon as the charging current reaches 10%, the current should be cut off. |
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