There have been studies done which point to a cycle being the full heating of the battery during a charge. Plugging in a battery for a few seconds doesn't heat it any noticible amount. Plug in that battery for an extended period and it will get decently warm. It is thought that the act of charging does less damage than the heating of the cell during charging. That is also the reason why batteries charged at 500mA suffer less damage than those charged at 2A.
I guarantee that if you had two batteries, one discharging and recharging fully and the other just discharging to 50%, the battery discharging to 50% would not be able to go through twice as many cycles.
Agreed, heat is the enemy.
There are inefficiencies involved when extrapolating out to the various possible combinations of charge/discharge quantities but the definition if a cycle remains the same.
If I charge and discharge at a low current level, where you don't involve heat and the inefficiencies it adds, then you can achieve the rated cycle life of a battery as defined. That's how the cycle life ratings are derived, at low current levels. We typically charge/discharge at much higher current levels than this, of course, so the cycling becomes less efficient. That doesn't change the fact that a cycle is not defined by every time you charge/discharge it where the battery gets hot.
These studies point to the things that affect cycle life, and they eventually might redefine what a true cycle might be, but there has to be a lot more to it than just saying if the battery gets warm/hot that's a full cycle. How hot? For how long? For which li-ion chemistries? How much do we derate the standard cycle life rating? IMHO, we can't just redefine an accepted rating definition because vaping batteries get hot.
Our batteries do get hot. You change the expected cycle life because of that, e.g., from 300 to 150. You don't change the definition of a cycle to compensate.
