My battery got really low (~ 7%). Is this OK?

Question

I was playing a very demanding game on my MacBook Air (2013) and after maybe an hour it said something about running on reserve power. The fan was constantly spinning at full speed (around 6000 RPM), and all the graphics settings were on maximum. I wish Mountain Lion would have had a low battery warning instead of just changing the color of the icon, which the game hides anyway. I use my laptop daily at university, and I usually get home after a 10 hour day with the battery around 25%. This is the first time ever that it has gone down below 10%. Did I damage the battery at all? (I think I heard it's not good to let it go below 15%.)

Answer 1

matthewfrommb wrote:
I was playing a very demanding game on my MacBook Air (2013) and after maybe an hour it said something about running on reserve power.
Gaming on battery, see 3B below
Forgetting about draining a battery low for a min. which is bad.
Fast / rapid drain on a battery while gaming is also bad.
When gaming, do so on POWER as much as you can, not on battery.
Example:
https://discussions.apple.com/thread/6034488?start=0&tstart=0
Contrary to popular myths about notebook batteries, there is protection circuitry in your Macbook and therefore you cannot ‘overcharge’ your notebook when plugged in and already fully charged.
However if you do not plan on using your notebook for several hours, turn it off (plugged in or otherwise), since you do not want your Macbook ‘both always plugged in and in sleep mode’.
Do not perform “battery calibration” on your current Macbook. There is no calibration of current Apple portable Macbooks with built-in batteries.
A lot of battery experts call the use of Lithium-Ion cells the "80% Rule", meaning use 80% of the full charge or so, then recharge them for longer overall life. The main quantified damage done in the use of Lithium Ion batteries are instances where the internal notebook battery is “often drained very low”, this is bad general use of your notebook battery.
All batteries in any device are a consumable meant to be replaced eventually after much time, even under perfect use conditions.
If the massive amount of data that exists on lithium batteries were to be condensed into a simplex, helpful, and memorable bit of information it would be:
1. While realistically a bit impractical during normal everyday use, a lithium battery's longevity and its chemistry's health is most happy swinging back and forth between 20% and 85% charge roughly.
2. Do not purposefully drain your battery very low (10% and less), and do not keep them charged often or always high (100%).
3. Lithium batteries do not like the following:
A: Deep discharges, as meaning roughly 10% or less. Avoid this in all instances if you can. This is hard on your battery.
B: Rapid discharges as referring to energy intensive gaming on battery on a frequent basis (in which case while gaming, if possible, do same on power rather than battery).
C: Constant inflation, as meaning always or most often on charge, and certainly not both in sleep mode and on charge always or often.
From Apple on batteries:
http://www.apple.com/batteries/notebooks.html
http://support.apple.com/kb/HT1446
"Apple does not recommend leaving your portable plugged in all the time."