iPhone 4 battery questions

Question

I have had an iPhone 4 with iOS5 for about 6 months.

• Is it good to wait for the battery to be almost 0% to recharge it?
• Is it good to recharge it to the fullest?
• Is it bad to leave the phone plugged to the computer/wall when it is already 100% charged?
• Is it bad never to charge the battery to its fullest?

Thanks.

Answer 1

This is from everythingicafe.com which is an unofficial source, but I have heard this same information about batteries many times:

So, what else can you do to increase your battery life? Charge it often. I’m serious! Apple uses Lithium Polymer batteries (not a straight lithium ion!), which perform best when you keep them “topped off”, meaning if you have a chance to charge it, then do it. I generally never let myself get below 45% unless testing due to what seems like unusual battery drainage. Apple also recommends that once a month you drain the battery down below 10% and then fully (uninterrupted) charge back to 100%. This is more for the battery meter than anything. It helps the meter get a correct reading on the battery and not display inaccurate information.

Source

Charging at least once a month keeps the electrons moving occasionally.

You can read what Apple officially says about batteries and how to maximize battery life.

Answer 2

Every deep discharge cycle of a li-ion battery will add up to reduce its life. So run the battery down to 0% as seldom as possible.

Shallow discharge cycles also reduce longevity a tiny bit, but more than proportionally much less than deep cycles. So keep the discharge shallow if possible.

Storage life of the battery is actually longest when partially charged. But if you are actually going to use your device as a mobile device, keeping the charge level nearly 100% will reduce the depth of any discharge plus full recharge cycles, and thus help maximize battery longevity. The smart charging circuitry will do this automatically if you leave it plugged in forever.

The recommended monthly full 100% discharge/charge cycles do nothing good for the li-ion battery itself. These full cycles just help the smart battery charging circuitry and the battery level meter/gauge to better calibrate themselves. A few times a year is probably more than enough to keep the battery gauge from going way out of calibration.