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About a week ago my battery status (MacBook Pro mid 2017) claimed that the battery should be replaced after 250 cycles. Now, all of a sudden the battery status has returned to normal.

ioreg -l -w0 |grep Capacity

| |           "AppleRawCurrentCapacity" = 4921
| |           "AppleRawMaxCapacity" = 5067
| |           "MaxCapacity" = 5067
| |           "CurrentCapacity" = 4921
| |           "LegacyBatteryInfo" = {"Amperage"=0,"Flags"=5,"Capacity"=5067,"Current"=4921,"Voltage"=12751,"Cycle Count"=251}
| |           "DesignCapacity" = 6669
| |           "BatteryData" = {"StateOfCharge"=98,"PMUConfigured"=0,"Voltage"=12751,"QmaxCell1"=5827,"AdapterPower"=1100127202,"SystemPower"=3035,"ResScale"=200,"QmaxCell2"=6504,"QmaxCell0"=6376,"CycleCount"=251,"DesignCapacity"=6669}

Is it possible somehow to identify the problem with the battery that evoked the message to replace the battery?

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Is it possible somehow to identify the problem with the battery that evoked the message to replace the battery?

From software?

Not really. Why? What you see there is a point in time measurement of your battery. You’d need a lab with a bunch of diagnostic equipment.

Think of it like the gas gauge in your car. It will only tell you at that moment how much fuel you have in your tank. Now, if you were to place a large brick inside your tank, the gauge will still be reporting accurately, but it would have no idea that the capacity would have changed by exactly the volume of the brick.

To accurately identify the problem, you you'd need to measure a number of things like how much fuel you used to fill it, how much you consumed over a period of time etc. The number of fill ups you made would be irrelevant.

Same for your battery. It’s not a single battery cell that we fill with angry pixies each time we charge it. It’s actually a series of cells and if, while discharging, it runs into a dead cell (meaning no charge in it), all of the point in time measurements will drastically change “setting off alarms” that you may have a bad battery.

It’s important to remember that when measuring voltage, it looks at the aggregate amount. If it runs across a dead cell, the aggregate voltage will change, but so will the charge capacity and available current.

Why does it do this?

There’s a good chance your battery is bad or in the process of going bad. The number of cycles is only a “rule of thumb” and not a hard and fast number. Batteries can die with 100 cycles and they can continue to function well after 1000 cycles. The bottom line is that they are man-made devices and not without manufacturing defects. While rare, they do happen.

So, can you determine the exact cause of a failing battery? If you had the time and resources, yes. However, the cost prohibitive nature of this means it’s much, much, more effective snd efficient to just replace it.

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If I understand correctly, your battery has a design capacity of 6669 mAh, but its actual capacity is 5067 mAh, or 76% of its design capacity. Given this, I wouldn't be surprised if macOS is indeed suggesting you replace the battery. While it's weird for that to happen to a battery less than 3 years old and with only 250 cycles through it, it's not impossible (I would speculate it's been subject to a lot of heat).

I suggest that you run through at least two cycles of full charge/full discharge and see if you still get the same capacity. While discharging, try to avoid drawing too much power (say, running CPU intensive apps, charging devices from your USB ports, etc.) if possible. Also, no partial charges: after a full charge, disconnect the power adapter, and don't reconnect it again until the computer shuts down because the battery drained fully. Now reconnect the power adapter and don't disconnect it until 100% charged.

If the capacity is still below 80%, I'd recommend calling Apple to ask about a free battery replacement -- I recall they claim 1,000 cycles for their batteries before their capacity drops to 80%. If you have AppleCare, I wouldn't be surprised if they agree. However, if they don't, even after insisting and pointing out the 1,000 cycle/80% specification, then be prepared to pay out of pocket to replace it soon -- after the 80% mark, things go downhill fairly fast.

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