Best way to run down phone battery?

[Sam3]

This is probably too late, but nevertheless...

You don't want to run down a lithium-ion battery, which what is in most electronic devices today. Running it down can actually shorten it's life, if not cause it to fail and become dangerous:

Wikipedia wrote: Most modern cell phones, laptops, and most electric vehicles use Lithium-ion batteries. These batteries last longest if the battery is frequently charged; fully discharging them will degrade their capacity relatively quickly.[citation needed] When storing however, lithium batteries degrade more while fully charged than if they are only 40% charged. Degradation also occurs faster at higher temperatures. Degradation in lithium-ion batteries is caused by an increased internal battery resistance due to cell oxidation. This decreases the efficiency of the battery, resulting in less net current available to be drawn from the battery.[citation needed] However, if Li-ION cells are discharged below a certain voltage a chemical reaction occurs that make them dangerous if recharged, which is why probably all such batteries in consumer goods now have an "electronic fuse" that permanently disables them if the voltage falls below a set level. The electronic fuse draws a small amount of current from the battery, which means that if a laptop battery is left for a long time without charging it, and with a very low initial state of charge, the battery may be permanently destroyed.

https://en.wikipedia.org/wiki/Battery_charger

Don't like or trust Wikipedia? Try this: http://batteryuniversity.com/learn/artic..._batteries

Interestingly enough they mention not to completely charge a Li-ion battery either.