Can anyone chime in on this
"I was under the impression that a battery is only damaged internally when theyare drained right down and left in that state over time causing a chemical reaction inside the battery ?"
"Incorrect uses of all batteries are excessive vibration, elevated heat and charging Li-ion below freezing. (See BU-410: Charging at High and Low Temperature.) Li-ion and lead acid batteries cannot be fully discharged and must be stored with a remaining charge. While nickel-based batteries can be stored in a fully discharged state with no apparent side effect, Li-ion must not dip below 2V/cell for any length of time. Copper shunts form inside the cells that can lead to elevated self-discharge or a partial electrical short. If recharged, the cells might become unstable, causing excessive heat or showing other anomalies"
Although not all batteries are the same it seems that time is the factor with li-ion above a certain level
"Don’t overdischarge them. Our batteries are rated down to 2.5V or lower but you can extend their life by staying above 2.8V-3.0V***. Going below 2.0V or so leads to metal being plated inside different parts of the battery, eventually causing an internal short circuit and possible bursting of the battery.es"