[qasdfdsaq]

Originally Posted by BenMcr

I always thought the full discharge / charge cycle advice was a hangover from older battery technology i.e. Ni-Cd batteries, rather than the Li-ion used today.

That is indeed correct. Li-ion chemistry doesn't benefit from full cycles and instead suffers excessive wear.

Same reason I thought as to why phones originally came uncharged with the advice to charge for 12 - 16 hours before first use, whereas now you normally have a reasonable charge out of the box.

Sorta. Most phones and batteries have always come partially charged. A partial charge of around 40% is the generally accepted optimal state in which to store a rechargeable battery of any type. Only, battery technology has gotten better, reducing internal self-discharge, and distribution networks have gotten faster, so a battery that left the factory at 40% charge has more of it left by the time it gets into your hands.

---------- Post added at 14:18 ---------- Previous post was at 14:15 ----------

Originally Posted by peanut

As for depleting the battery, maybe that's an IOS thing as that's what I've been told. And only do it on initial charge and obviously not recommended to be done often. But it does calibrate the battery gauge on IOS which is recommended to be done every few months. Still if that's wrong, then I'm happy to be corrected, seems everyone says something different unfortunately. But qasdfdsaq cheers for the heads up.

Indeed, the 'recommendation' to do a full discharge on iOS is to 'recalibrate' the battery gauge/meter/monitoring circuitry. It does not apply to all platforms, partly because on phones with removable batteries, the calibration circuitry is built into the battery, not the phone.

---------- Post added at 14:22 ---------- Previous post was at 14:18 ----------

Originally Posted by alferret

Yea the full charge/discharge is a throwback to Ni-Cd batteries and it can harm newer lithium batteries.

Indeed, this is correct too.

I should add, doing an 'operational discharge' - running your phone until it's empty - just wears the battery down without much damage, as long as you charge it reasonably soon after.

Doing a 'full discharge', as in to continue draining it even after your phone dies (e.g. with a battery-discharger, resistor, etc.) can do damage. Draining Li-ion batteries below a certain voltage per cell will permanent physical damage but most batteries have self-protection circuitry that will disconnect the cells at a safe level to stop you from doing this.

However if you drain it until said cut-off, and then don't charge it for some time, internal self-discharge can cause the voltages to drop even further, beyond the safe limit imposed by the circuitry. That's really bad for the battery.