Iphone battery life: drain or not drain?

You can't overcharge the battery. Don't let it drain to dead, no need to. The battery does not have a memory.

It's not necessary to completely drain the battery before charging.

I don't believe you can overcharge the battery. If the iPhone remains plugged in after the battery is fully charged, charging stops.

With a Lithium-ion battery, you can charge the iPhone's battery at any battery level. There is no memory effect with a lithium-ion battery.

Copied from the link you provided:

For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally. Be sure to go through at least one charge cycle per month (charging the battery to 100% and then completely running it down).

By definition, a full charge cycle can mean going from 100% to 50% followed by charging to 100% one day - which equals 50% of a full charge cycle, followed by doing the same the next day equals a full charge cycle.

Going from 100% and then completely running the battery down until your iPhone shuts off automatically does more for calibrating the battery indicator than anything else, but since Apple recommends going from 100% and then completely running it down once a month, this is probably a good idea.

In between, you can charge your iPhone's battery to 100% when at any level.

Hi i3g,

You do not have to drain the battery completely before charging it.

"You can also recharge a lithium-ion battery whenever convenient, without the full charge or discharge cycle necessary to keep nickel-based batteries at peak performance. (Over time, crystals build up in nickel-based batteries and prevent you from charging them completely, necessitating an inconvenient full discharge.)" http://www.apple.com/batteries/

-Jason

I charge mine whenever I'm near a charger. I leave it on the charger overnight, every night. You can't overcharge it.

Once a month or so I run the battery down completely (using a playlists of 101 music videos) and then recharge it. Which is what the link you posted recommends.

I leave WiFi on, 3G on, bluetooth on, push off, 2 min auto-lock, auto-brightness on and brightness at 1/2. I have no battery problems.

I saw somewhere that the battery has 400 life cycles. I thought that the cycle counts whenever you charge it .. meaning charging on 50% battery will count as one cycle and kill battery lifespan.

Not true or not accurate.

Copied from this link - the same link you provided in your post.

A properly maintained iPhone battery is designed to retain up to 80% of its original capacity at 400 full charge and discharge cycles. You may choose to replace your battery when it no longer holds sufficient charge to meet your needs.

It isn't a life cycle - it is a charge cycle.

A full discharge and charge cycle is going from zero to 100%. In the example I gave, if you go from 100% to 50% and charge the battery to 100%, this counts as a 50% discharge and full charge cycle. If you repeat this the next day, this amounts to one full charge cycle. Over the two day period in this example, you did one full discharge and charge cycle - 50% one day, and 50% the next day.

If you wait until your battery level is at 20% and charge the battery to 100%, this amounts to an 80% full discharge and charge cycle. If you charge your battery 100% the next day when at 80%, this amounts to a 20% full discharge and charge cycle. Over the two day period in this example, you did one full discharge and charge cycle - 80% one day, and 20% the next day.