Battery cycle count inaccurate

[tploumen]

I've got a new Macbook Air M3 since 17 juli 2024. From the start I kept an eye on the battery cycle count.

What is striking is that when approximately 89-90% of the battery has been used, a new cycle is calculated. For instance I did this test:

My cycle count went from 9 to 10 when I was at 32,4% battery charge. I used the battery till 20% battery charge left. So that is effectively 32,4 - 20 = 12,4% of 1 cycle.

I then recharged to 80,06%, unplugged and used the battery till 42,2% was left. So that is effectively 80,6% - 42,2% = 37,86% of 1 cycle.

I then recharged to 100%, unplugged and used the battery till 73,9% was left. So that is effectively 100% - 73,9% = 26,1% of 1 cycle.

I then recharged to 100%, unplugged and used the battery till 86,5% was left. So that is effectively 100% - 86,5% = 13,5% of 1 cycle. At 86,5% the cycle count went from 10 to 11.

So in total I used: 12,4% + 37,86% + 26,1% + 13,5% = 89,86% of 1 cycle. There should be 100% - 89,86% = 10,14% left. But my cycle count went 1 up! And it does this all the time at 89-90% of 1 cycle.


Who wants to test for me whether this is also the case with him...?

To do this, you must first wait until the Mac shows a new cycle (in System Viewer). Then write down the battery percentage. You then deduct your consumption from that each time. Suppose you get a new cycle at 85% and you use your Mac on battery up to 25% (you have effectively used 60% of a cycle). You then charge again to 100% and then use the battery again to 60% (you have then effectively used 40% of a cycle). In total you have used 60% + 40% = 100% = 1 cycle.

In my case, a new cycle appears in System Viewer every time after 89-90% battery consumption.

 

[MacCheetah3]

It’s battery charge cycles, not battery discharge cycles. I know it seems like the same thing but it’s not.

I used the battery till 20% battery charge left. […] I then recharged to 80,06%

So, that’s 60.06% charge.

unplugged and used the battery till 42,2% was left. [...] I then recharged to 100%

This is 57.8% charge. 57.8% + 60.06% = 117.86% So, now you're more than one full cycle.

unplugged and used the battery till 73,9% was left. [...] I then recharged to 100%

26.1% charge

Now the battery has been charged 60.06% + 57.8% + 26.1% for a total of 143.96% or ~1.44 cycles

 

[tploumen]

It’s battery charge cycles, not battery discharge cycles. I know it seems like the same thing but it’s not.


So, that’s 60.06% charge.


This is 57.8% charge. 57.8% + 60.06% = 117.86% So, now you're more than one full cycle.


26.1% charge

Now the battery has been charged 60.06% + 57.8% + 26.1% for a total of 143.96% or ~1.44 cycles

I appreciate your answer, but you are incorrect. 1 cycle = when 100% of the battery charge has been used. This can be spread over several days. As long as your discharge sum is 100%.

This is what Apple says on their website:

About battery cycles​

When you use your Mac laptop, its battery goes through charge cycles. A charge cycle happens when you use all of the battery’s power—but that doesn’t necessarily mean in a single charge.

 

[MilaM]

About battery cycles​

When you use your Mac laptop, its battery goes through charge cycles. A charge cycle happens when you use all of the battery’s power—but that doesn’t necessarily mean in a single charge.

I'm just speculating here, but maybe the algorithm Apple uses tries to account for the fact, that cycling batteries down to 0% and up to 100% is more detrimental to the long-term health of the battery. Using your batter from 30% down to 0% is, for example, worse than using the same amount of energy around the 50% mark.

 

[MacCheetah3]

I appreciate your answer, but you are incorrect. 1 cycle = when 100% of the battery charge has been used. This can be spread over several days. As long as your discharge sum is 100%.

This is what Apple says on their website:

About battery cycles​

When you use your Mac laptop, its battery goes through charge cycles. A charge cycle happens when you use all of the battery’s power—but that doesn’t necessarily mean in a single charge.

I did reread Apple’s explanation after posting, and sadly, even they make it a little confusing. The portion Apple leaves out (or at least doesn’t describe well) is a full cycle is really the full discharge-charge process. That is, discharging 100% is only half the process, you need to replenish what was depleted.

A quick analogy:

You’re given a full (100%) glass of water. You drink half (-50%), then someone refills it (+50%). Next, you consume three quarters (-75%). It gets refilled again (+75%). As you sip on the water, the glass is only one third empty (-33%). before the server makes a refill (+33%) round. You consume all of the water (-100%) and the server refills the glass (+100%) once more. You eventually finish, leaving the empty glass (-100%).

Consumption: -50 -75 - 33 - 100 = -258 or 2.58 glasses of water drank
(Re)Filled: 50 + 75 + 33 = 158 or 1.58 glasses worth of water provided to you

The value is 1 short because to complete the cycle we need to refill the glass (i.e., recharge the battery) for the next time.

I hope that makes sense.

#####

To circle back — no pun intended, just a nice coincidence of word choice — that’s why I feel it’s easiest to simply add up the charged percentages like I did in my original reply.

 

[tploumen]

I did reread Apple’s explanation after posting, and sadly, even they make it a little confusing. The portion Apple leaves out (or at least doesn’t describe well) is a full cycle is really the full discharge-charge process. That is, discharging 100% is only half the process, you need to replenish what was depleted.

A quick analogy:

You’re given a full (100%) glass of water. You drink half (-50%), then someone refills it (+50%). Next, you consume three quarters (-75%). It gets refilled again (+75%). As you sip on the water, the glass is only one third empty (-33%). before the server makes a refill (+33%) round. You consume all of the water (-100%) and the server refills the glass (+100%) once more. You eventually finish, leaving the empty glass (-100%).

Consumption: -50 -75 - 33 - 100 = -258 or 2.58 glasses of water drank
(Re)Filled: 50 + 75 + 33 = 158 = 1.58 glasses worth of water provided to you

The value is 1 short because to complete the cycle we need to refill the glass (i.e., recharge the battery) for the next time.

I hope that makes sense.

Thank you! So you are actually saying that the cycle count calculation in my MBA M3 is correct...? (and even on the conservative side)

Are you 100% sure and may I ask how you know this information...?

 

[MacCheetah3]

Thank you! So you are actually saying that the cycle count calculation in my MBA M3 is correct...?

Yes.

Are you 100% sure and may I ask how you know this information...?

A few quick sought sources:

How Battery Cycle Count Affects the Lifespan and Performance of Your Device

Learn how to determine the cycle count of your battery and how many times it has been charged and discharged.

pluginhighway.ca

What is a Battery Cycle Count and How Does it Impact Performance?

Unveiling Battery Cycle Count: Understand its impact on performance, lifespan, and power management. Learn more now!

batteryhacker.com

 

[tploumen]

Yes.


A few quick sought sources:

How Battery Cycle Count Affects the Lifespan and Performance of Your Device

Learn how to determine the cycle count of your battery and how many times it has been charged and discharged.

pluginhighway.ca

What is a Battery Cycle Count and How Does it Impact Performance?

Unveiling Battery Cycle Count: Understand its impact on performance, lifespan, and power management. Learn more now!

batteryhacker.com

I really appreciate your effort to help me. Though before you posted your last post I contacted Apple Support. They said that my calculation was correct, though they didn't have a reason why a new cycle was calculated after 89-90% discharge.

Though I think I've found my answer:

Batteries - Why Lithium-ion?

Learn why Apple rechargeable lithium-based technology provides the best performance for your iPhone, iPad, iPod and MacBook.

www.apple.com

In the footnote it says:

* A complete charge cycle is normalised between 80% and 100% of original capacity to account for expected diminishing battery capacity over time.

I still find this a little bit strange since my new Macbook Air M3 still has 100% capacity after 11 cycles and according to coconutbattery it even has 101% battery health.



If anyone could test this on their system I would be really gratefull...!

 

[MilaM]

* A complete charge cycle is normalised between 80% and 100% of original capacity to account for expected diminishing battery capacity over time.

Interesting find. Can someone knowledgeable maybe chime in and explain what this means in simple words?

 

[f54da]

It means that as battery undergoes cycle and calendar aging, the 100% mark on the gas gauge no longer corresponds to 100% of the original capacity, as that will never be able to be reached. Instead it's always normalized to 100% of the current estimated capacity.

Take a look at https://www.ti.com/lit/an/slua364b/slua364b.pdf?ts=1613743898155

 

[MilaM]

It means that as battery undergoes cycle and calendar aging, the 100% mark on the gas gauge no longer corresponds to 100% of the original capacity, as that will never be able to be reached. Instead it's always normalized to 100% of the current estimated capacity.

Take a look at https://www.ti.com/lit/an/slua364b/slua364b.pdf?ts=1613743898155

Thanks. I wasn't sure what normalizing means in this context. Your explanation makes sense.

 

[Chancha]

I still find this a little bit strange since my new Macbook Air M3 still has 100% capacity after 11 cycles and according to coconutbattery it even has 101% battery health.

This one bit is because Apple choses to always report any >100% capacity as 100%, probably to make it less confusing for some (most) people who may struggle against the idea of the meaning of >100%. This is why sometimes you can spend two hours watching videos on a MacBook on battery, at the end macOS still says it is at 100% as if no energy was used, while in fact it actually went from say 104% to 100% for example.

Then coconutBattery just reports it as is. The "designed capacity" is often just a target, a given battery can be shipped above or slightly below it depending on many factors.

 

[tploumen]

I swapped my new Macbook Air M3 for a new one because I didn't trust it. The new Macbook Air M3 did exactly the same: it went from cycle count 1 to 2 after a total discharge of 89%. The full charge capacity on my new Macbook is even 103,2% according to CoconutBattery.

The only thing I cannot get to work is Optimized Battery Charging. I use it every morning and in the afternoon on battery. In the evening I use it for 5 consecutive hours plugged on AC. I've been doing this for 15 days in row now and it still charges to 100% and stays there.

 

[BigBlur]

The only thing I cannot get to work is Optimized Battery Charging. I use it every morning and in the afternoon on battery. In the evening I use it for 5 consecutive hours plugged on AC. I've been doing this for 15 days in row now and it still charges to 100% and stays there.

This sounds like expected behavior to me since you're only charging 5 hours per day. What exactly are you expecting it to do? When Optimized Battery Charging is in effect, it will charge to 80%...and then charge to 100% when it predicts you'll be unplugging soon based on your usage patterns. It's designed more for those that use their Mac plugged in for an extended period of time.

If Optimized Battery Charging even works in your scenario, it would be charging to 80% during the first few hours, and then to 100% during the last couple hours or so. Not sure if the battery sitting at 100% for two-ish additional hours is really going to have that much of an impact on battery health, so maybe macOS doesn't apply Optimized Battery Charging since it knows you're going to be unplugging soon.

 

[tploumen]

This sounds like expected behavior to me since you're only charging 5 hours per day. What exactly are you expecting it to do? When Optimized Battery Charging is in effect, it will charge to 80%...and then charge to 100% when it predicts you'll be unplugging soon based on your usage patterns. It's designed more for those that use their Mac plugged in for an extended period of time.

If Optimized Battery Charging even works in your scenario, it would be charging to 80% during the first few hours, and then to 100% during the last couple hours or so. Not sure if the battery sitting at 100% for two-ish additional hours is really going to have that much of an impact on battery health, so maybe macOS doesn't apply Optimized Battery Charging since it knows you're going to be unplugging soon.

Then why does it work so on Iphone:

* Optimized Battery Charging needs at least 14 days to learn your charging habits, so it won't engage before then. Also, your iPhone needs to experience at least 9 charges of 5 hours or more in a given location for Optimized Battery Charging to engage.

Source: https://support.apple.com/en-us/108055

 

[BigBlur]

Then why does it work so on Iphone:

* Optimized Battery Charging needs at least 14 days to learn your charging habits, so it won't engage before then. Also, your iPhone needs to experience at least 9 charges of 5 hours or more in a given location for Optimized Battery Charging to engage.

Source: https://support.apple.com/en-us/108055

That statement is a bit vague/unclear, imo. Personally, I think it means that needs to happen to allow Optimized Battery Charging to engage at that given location...not that it will engage.

These statements are found elsewhere on that page:

Optimized charging is designed to engage only in locations where you spend the most time, such as your home and place of work.

Possibly referring to the "9 charges of 5 hours or more" rule?

Your iPhone uses on-device machine learning to learn your daily charging routine so that Optimized Battery Charging activates only when your iPhone predicts it will be connected to a charger for an extended period of time.

Does Apple consider 5 hours to be an extended period of time? In my experience, if I plug my phone in around 10pm or so, I will see optimized charging kick in. If I happen to have a late night and plug in around 1am or so, I do not see optimized charging kick in despite me always unplugging my phone around 7am when I wake up.