[Samsung Galaxy Note 8 Accessories] Huele Fello:
From my point of view it's wrong. There could be some circumstances where the 35% is correct, but in general it is best to not discharge batteries down to those levels too many times, because the discharge cycle changes the chemistry inside the battery such that it doesn't accept the full amount of charge that it accepted prior to the deep discharge. The chemistry changes significantly when you deep discharge down to the single digit percentages and less as as you go up to 50%. My batteries have discharged deeply in the past but they were few and far between. I speculate that when I sold my Nexus 6 about 1.5 months ago, its battery capacity was about 98% due to my careful diligence.

Now why should you take my word on this? I can ask you the same question about the 35%. Why should you take his word on it? My opinion comes from decades of electrical engineering work, mostly in programmable devices and ASIC development, but some of it is in testing. I was hired as a consultant to test batteries for aircraft prior to the lithium-ions showing up in aircraft. We found that lead-acid batteries changed chemistries significantly when they were deep discharged. This is evident when people have cars that sit for a while. The batteries have normal self-discharge and need to be charged when the car owner finally gets around to wanting to start the engine. That really wears a battery down, and they make trickle chargers to prevent batteries from deep discharging.

Then came the lithium-ions. These tests by the way also involved testing of charging curves or how the voltage on the batteries are changed as they charged. We found two things. One is lithium-ions behave similarly to lead-acid batteries when deep discharge cycles occur. Both types of batteries lose some capacity. There are different lithium-ion chemistries, but they all seem to have the same characteristics with deep discharge cycles. The other thing we found is that most devices have smart chargers in order to prevent lithium-ion fires. They will take a large voltage and convert it to a charging cycle voltage that varies depending on where the charge percentage is. While these chargers are sold to make them look like they're tweaking the hell out of the batteries' capacity, they're mostly there to achieve 100% charge and prevent fires. These chargers not only monitor the batteries' internal voltage but also their temperature.

With our smartphones, this all boils down to chargers simply providing enough power to allow the internal smart charger to charge the battery efficiently, safely and quickly. I've found the Tylt Vu will charge a Nexus 6 and Note 8 sufficiently enough to where it can be used and gain charge simultaneously. As far as deep discharge cycles are concerned, I have actual lab test knowledge of battery charging and discharging, and I've applied this knowledge to my phones and many other devices. In all cases, I have always been able to preserve my batteries such that when I sell them, the new owner gets what I consider a very good OEM installed battery. One of the perils of buying used electronics is the condition of the battery, and I explain this to my buyers. I've always had happy buyers that never complained after the sale.