Lengthen Battery life

Apple iPhone - Lengthen Battery life

My husband was browsing on his iPhone and up popped a suggestion that to lengthen the life of the battery, one should keep the battery fully charged but occasionally let it run down to almost nothing. Is that correct? I keep my 4 charged fully most of the time and have never let it go down below 75%.

iPhone Battery
The iPhone has a battery that is unlike older "NICAD" batteries that would benefit from letting it run down. Lithium batteries do not have a memory like Nicads do so its really not necessary. I recharge when it gets down to about 20%. Either way will work.

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Yes that's true it let's the iPhone know the hi & low of the battery & if you let it go down to almost nothing then the battery will last longer in the long run usually I'll let the battery drain if I'm not going anywhere & I'm staying in the house all day

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It seems that old myths die hard - I should submit this one to the Mythbusters.

The truth is - with Lithium Ion batteries your fully charged cell voltage is around 4V. If the battery ever discharges below 2.5V, it is unrecoverable. The good news is - that almost never happens. Lithium Ion batteries are so dangerous - there are sophisticated charging circuits controlling them. Part of the function of the charge circuit is to optimize life - if the battery is fully charged, the charging circuit shuts down before any potential damage could happen from overcharging. Similarly, if the cell has dropped below 2.5V, it will not attempt to charge it.

Bottom line - fully discharging a Lithium Ion battery is flirting with the lower cell voltage limit, and repeatedly doing this could fool the charging circuitry into thinking the battery is unrecoverable.

As with any rechargeable battery, you shouldn't attempt charging unless the phone is at room temperature. Charging when the battery is hot or cold can damage it - and the charging circuit may contain a temperature sensor to keep the battery from charging until it is in a safe temperature range.