It is not normal. If your device is mostly plugged in, you should limit battery charge to 80% or less to preserve battery capacity. Many laptops indeed have an option to limit charging in firmware settings, or the OS can do that.
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No, it is not normal. On the contrary, BMS in laptops usually tries to prevent it as much as possible, e.g. by not recharging until battery level drops below 95% or even 90%.
I didn’t say anything about DAMAGING the battery. I said that both high and too low voltage are harmful for it, obviously in terms of excessively degrading its capacity and life time, but not damaging it.
Nominal voltage of lithium cells is 3.6 - 3.7 Volts. Maximum voltage should be <= 4.2 Volts. Minumum voltage should not drop below some 2.8 - 3.0 Volts. The best for a lithium cell is to keep its voltage as close to the nominal voltage as possible - this is what gives it the longest life time and performance. That’s why good Li-Ion chargers offer a “Storage” mode that charges the battery only to 3.8 Volts as with such a voltage it can be safely stored for years.
Obviously, charging the battery only to 3.7 - 3.8 Volts would allow to only use part of its capacity, that’s why they’re being usually charged to 4.2 Volts. Which is a TRADE OFF: more capacity to use in exchange for reduced life time. But as you can easily check with e.g. AIDA64, on your Sony Xperia smartphone in final charging phase battery voltage reaches even 4.5 Volts. Sony’s lithium cells have slightly modified structure and chemistry to safely using such higher voltage (and thus higher capacity) but still at the cost of reduced life time. Sony probably tries to circumvent it with their proprietary technologies (Stamina etc.) trying to save the battery in some other areas so that at the end of the day you end up with the same battery life as others, but I don’t think that those proprietary technologies work on SFOS.
“Battery users want to know if Li-ion cells with higher charge voltages compromise longevity and safety. There is limited information available but what is known is that, yes, these batteries have a shorter cycle life than a regular Li-ion; the calendar life can also be less. Since these batteries are mostly used in consumer products, the longevity can be harmonized with obsolescence, making a shorter battery life acceptable. The benefit is longer a runtime because of the gained Wh (Ah x V).”
Also read this whole article:
For example this part: " Figure 5 demonstrates cycle count as a function of charge voltage. At 4.35V, the cycle count of a regular Li-ion is cut in half."
Well, so it is actually not THE SAME drainage but considerably smaller than in my case, as my 10 III only lasts 24 hours or less when switched to use 4G network. On 2G it easily lasts 2+ days, though.
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