On Dec 24, 2012, at 8:00 AM, Dinse, Gregg (NIH/NIEHS) [V] wrote:

> On Dec 23, 2012, at 7:51 PM, Macs R We wrote:
> 
>> On Dec 22, 2012, at 11:19 PM, Dinse, Gregg (NIH/NIEHS) [V] wrote:
>> 
>>> I thought the number of power cycles was the most important factor in 
>>> determining when a battery would need to be replaced.  This is why I was 
>>> asking about the length of time between charges.  If I charge the iPad each 
>>> night, but the battery would actually last for a week without recharging, 
>>> won't the battery need replacing 7 times sooner?  I'm guessing that it 
>>> won't really be 7 times sooner, but you get my point.  Or is that just a 
>>> myth?
>> 
>> I'm not positive about iPads, but on Macs, fractional recharges are 
>> accounted for as fractional recharges.  That is, if you recharge a battery 
>> from 50%, it's counted as half a power cycle, not a full one.

Official confirmation here:

http://www.apple.com/batteries/

Note that this is not necessarily true of older technology batteries.

> That's interesting.  If a fractional recharge counts as the same fraction of 
> a power cycle, then it should not matter how frequently or infrequently the 
> battery is charged, at least with respect to the impact of power cycling on 
> overall battery longevity.

Either that, or it further divorces the reported cycle count from the 
real-world longevity prediction.  For example, we know that batteries with 
extremely low cycle count (because they are hooked up to AC all the time) 
actually tend to fail fastest.

> If that's true, and I'm certainly not saying it isn't, that seems like good 
> news for those of us who have been trying to monitor battery status and wait 
> until the battery is low.
> 
> Thanks for the information.

-- 
  Macs R We -- Personal Macintosh Service and Support
    in the Wickenburg and far Northwest Valley Areas.
                            http://macsrwe.com

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