New 2017 Air - battery design capacity / noisy fan

I've just got a new 2017 Air direct from Apple. Having used it for nearly a week now I am noticing two odd things -

1- On my older Macs Coconut battery would always show the Design Capacity as 100%. For the Air, however, it is fluctuating a little bit and ranging from 99.1 to 100%. How is this possible?

My impression was that it starts coming down from 100% after a year or more of use. At least, that is how it was like with my previous Mac. Could be some hardware issue with the battery?

2- Coconut also tells me that the battery on my new Air is actually 121 days old. Is this normal for a new laptop? Thankfully the charge cycle was only 1 when I booted it up for the first time.

3- Also, the Mojave is over-reporting the battery level by about 4.5%. Coconut shows 65.5% and the Mojave says 69%. Is this normal?

2- I have heard about how the Air has a noisy fan. I can hear it go on at a steady drone for not less than 10 mins now!
Right before typing this I had watched youtube videos for about 20 mins. But the laptop has not heated up at all and room temperatures are 68 ºF. The area around the function keys is normal and cool to the touch. So, why is the fan on and that too for so long? Is this just how the Air is?


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I agree that battery charge should no longer be at 100%

There are long discussions why so I won't write much except to get more life out of the battery (not to be confused with run time) we should let the battery drift down before topping it up.

2. Why is this a concern? From time of manufacture to deliver can be months. I'm going with normal.

3. Again, normal. If the battery had it's own computer to report charge level then I'd agree but it doesn't so as you change OSes I bet the values change.

Fan noise. As we moved away from HDDs the fans became the next noisy part. I see nothing wrong here. I drive an EVcar (electric vehicle) and hear different sounds as there is no ICE (internal combustion engine.) I doubt anyone will reveal Apple's design decisions on the fan timing. But it's best to let it run at low speed rather than let heat build up.

Post was last edited on April 5, 2019 11:03 AM PDT

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I should correct my post a bit. The measurements of these batteries are never accurate. They have always been estimates and will completely upset folk that thought that this was all science and fact when it is not.

On top of that, as the temperature changes so does the battery capacity and available AmpHours. With so many factors if you see some movement I'm calling this normal. This will only concern those that think there is something wrong. Nothing wrong at all. It's been this way since day zero.

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That's reassuring to hear

So, what do you suggest?

I am thinking that maybe for the next 2-3 cycles I will just take the battery down to 10% and then charge it up all the way to 100%. I won't leave it on 100 because I know that induces high voltage stress in the battery. I'll take it off the charger soon as I the light on MagSafe2 turn green.

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Why wear down a battery like that?

There's some old battery advice (thanks Internet) that doesn't apply to Lithium batteries. So if you want to wear down the battery you would do that.

The drain and charge was advice for old, can't find a laptop with them today NiCad batteries.

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