How many times can I charge my iPhone's battery?

[Red Barchetta]

So I just got a new iPhone and am coddling it like a baby. As such, I want to maximize it's battery life so I don't have to send it in for replacement anytime soon.

It's to my understanding that the iPhone uses a Lithium Ion (cobalt) battery, which evidently is good for 300-500 charges, before its capacity is reduced to 80% of what it once was.

Now here's my question: What exactly constitutes a charge? If I plug it in for only 5 minutes, is that one charge? Or does it have to have a complete discharge/charge cycle to count as one? What if come home and plug it in every night, regardless of its remaining charge? Should I expect to have a reduced battery in less than a year?

So what's the best way to treat this battery?

[slaphead]

Originally Posted by Red Barchetta

So what's the best way to treat this battery?

I believe partially discharging and rechargin again, at low/moderate temperatures. Any discharge followed by a charge counts as a cycle, even if it's only a few percent. They don't like being kept at 100% plugged into the charger, or being fully drained. I am not a battery expert, however.

I did turn up this battery-obsessive page which appears reputable and seems to answer most of your questions.

[xash]

Apple battery FAQ:
http://docs.info.apple.com/article.html?artnum=62018

"
Question: Do I need to completely empty the battery before charging it, and does doing this prevent the so-called "memory effect"?
Answer: You don't need to empty the battery before charging it. Lithium-based batteries, like those used in iPod, have none of the memory effects seen in nickel-based rechargeable batteries.

Question: Should I leave iPod connected to the charger or in the dock whenever I'm not using it?
Answer: The battery stops charging when it's full. Leaving it connected won't charge it any more. It's perfectly OK to leave it connected so it can charge overnight, for example.

Question: Is it better to empty the battery before charging it, or can I charge it whenever it's convenient?
Answer: You can charge iPod's battery whenever it's convenient.

Lithium-ion batteries need to be used for maximum performance. If you don't use your device often, be sure to complete a charge cycle at least once per month.
"

Apple iPhone battery tips:
http://www.apple.com/batteries/iphone.html

"
Use iPhone Regularly

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).
"

Charge cycle explained:
http://www.apple.com/batteries/

"
A charge cycle means using all of the battery’s power, but that doesn’t necessarily mean a single charge. For instance, you could listen to your iPod for a few hours one day, using half its power, and then recharge it fully. If you did the same thing the next day, it would count as one charge cycle, not two, so you may take several days to complete a cycle. Each time you complete a charge cycle, it diminishes battery capacity slightly, but you can put notebook, iPod, and iPhone batteries through many charge cycles before they will only hold 80% of original battery capacity.
"

[ASAKMOTSD]

I figure there will be a couple new generations of the device out before my battery dies. I am not worried. It will probably be time to upgrade regardless. (I swear I did not drink that kool-aid from Steve Jobs).

[Cleophus]

"Charge cycles" refers to using the battery's full capacity. So, if you use 25% of the battery's capacity each day and recharge it every day, after 4 days you will have used one charge cycle.

[Red Barchetta]

Originally Posted by Cleophus

"Charge cycles" refers to using the battery's full capacity. So, if you use 25% of the battery's capacity each day and recharge it every day, after 4 days you will have used one charge cycle.

Awesome, that's really good to know. Thanks all for the answers!

[Earl Snake-Hips Tucker]

While I have no reason (or background) to doubt Apple's FAQ, I wonder about their use of the term "memory effect." Didn't we show a long time ago that the performance degradation wasn't due to battery, uh, "memory" of previous charges?

[IAmNotSpartacus]

Originally Posted by Earl Snake-Hips Tucker

While I have no reason (or background) to doubt Apple's FAQ, I wonder about their use of the term "memory effect." Didn't we show a long time ago that the performance degradation wasn't due to battery, uh, "memory" of previous charges?

Not sure what you're getting at here, but battery memory is a well-documented and understood concept. The above link, www.batteryuniversity.com, is courtesy of a company (Cadex) that pioneered automated rechargeable battery analysis and conditioning.

Simply put, crystals will form in the battery paste if not fully discharged and charged, and those crystals impact the paste's ability to absorb and retain power. Since the proportion of paste that crystallized is directly related to the level of charge/discharge, it's not unreasonable to describe the effect as memory.

[beowulff]

Except Lithium batteries don't experience a memory effect, like NiCd batteries do.

[IAmNotSpartacus]

That is correct, lithium based batteries do not suffer from memory effect.

And it's not just Nickel Cadmium batteries that suffer memory, to a lesser extent Nickel Metal Hydride batteries will also suffer from memory effects.