Will keeping MBA M2 attached to 10W or 30W charger while using reduce battery cycles?

[1BadManVan]

The battery probably had a few cycles on it from the factory during tests. If not, partial charges, even if you just put the charger on for a short period of time, will still increment those cycles over time.

It had 1 cycle on it from new and nope, just a total of 5. Oh well, this one’s going back anyways, was just trying to make sense of these cycles

 

[Brian33]

I find OP's idea interesting, but it's just a guess that limiting the charge rate to approximate the consumption rate during continuous/extended use is beneficial to battery life. I'd like it to be true, but I don't know of any evidence that supports it.

I hate to be a naysayer, but if using such a charger had noticeable (or at least measurable) benefits, it seems to me that some company would be making and marketing them as such. It could have a switch on it to change from 10W "daytime use" mode to 65W "full charge" mode, for example. It wouldn't take much money for a company to fund a little research on Li-ion batteries and use the (presumably) positive results in their marketing. Anker is missing the boat! Anyone want to invest in a start-up? ;-)

I'd like to be wrong... maybe there is some evidence in favor of the idea...

(Note -- I'm not talking about the "limit charge to 80% and discharge to 20%" idea.)

 

[Don MC]

Don,
I am hoping you needed to use a female USB-c to male USB-a adapter to test your iPad charger to charge your MacBook Air. If so, what brand and specific adapter did you use (link would be very helpful)? Last night I wanted to initially buy one of these adapters, but some reading led to confusion if between which USB spec (USB 3.0 vs 3.1, or even 2.0) would work or not work for this charging scenario. I gave up researching when I could not find any definitive answers. So, if you have one that works... I want that specific one! 🙂

What MBA year, model did you test on?

No fancy adapters. Just a male USB-A to male USB-C cable. No brand.
The chargers in question both have female USB-A connectors.

My MBA is a 2022 M2. Base model, 8GB/256GB.

 

[davekro]

Don,
Cool signature, dude. 😎
Any chance you can look up where you bought it and see if it listed as USB 2.0, 3.0, or 3.1.
Maybe the partial info I saw implying some USB spec version(s) would not work. Though I was focusing just on ability to charge, not data transfer, maybe the no-go I saw on one spec. (3.1 maybe?) meant for data. I don't recall.

Good to see your low watt charging experiment was Apples to Apples with my machine. 😛
I'll see what happens when I get my 20W Anker Nano PIQ charger for rate of charge and if it gets hot when charging from say a 20% SoC.

 

[davekro]

Honestly, using such a low power charger might actually do more harm than good in terms of battery cycle counts. If you have a 10W charger and the computer needs to pull 15W (even instantaneously, for a split second), it's going to pull that extra power from the battery. Even if you're using a tool such as Aldente to limit charging percentages, it's going to have to replenish that power back into the battery. This adds to cycle counts and uses the battery more.

Cycle counts themselves also aren't really a measure of the total wear of the battery. They are just a number. My old 2012 MacBook pro has over 1,860 cycles on the original battery and it's still at 87% battery health. Lithium Ion batteries love partial charges, especially in the range of 20% to 80%, so charges in that range do much less damage to the battery than states of charge that are outside of this range. Using such a low power charger is likely going to result in a lot of these tiny little partial charges, which won't do a ton of harm to your battery in those ranges, but it will still increase cycle counts over time and will likely still negate any benefits you get from using such as slow charger.

The best thing you can do for your battery health is honestly just to keep it in a healthy 20-80% range as much as possible. This is where the most benefits are in terms of protecting battery longevity. Tools like Aldente are great for this.

I get your point if machine use watts consumption peaks above a low level charge wattage. Thanks for that thought to consider.

I have my AlDente App limit SoC to 75% and will make every effort not to let the SoC drop below 20%*. During a work day, being plugged in until the end of that day's use, both my Apple 67W and ordered Anker Nano 20W chargers would keep the MBA M2 battery topped off at the 78% SoC level (AlDente set at 75%). I'll have to see if I can tell from iStat Menus if I ever see any actual charging. When I have looked, I see zero watts and zero mA. So far, AlDente seems to maintain a 78% charge, 3% over my set limit of 75%. No big deal.

1) Would the Apple 67W charger's charging profile or the Anker PIQ (PD+) 20W's charging profile with AlDente set at 75%, not actually send current to the battery in a 10-hour work period? Would both chargers just regulate their watt/voltage output to match the ≈ 7.5 watt normal use rate, and jump up to cover the very infrequent spikes to 9 or 10 watts?
2) Would whatever VERY minimal charging over say a 10-hour work period be about equivalent to making up for say the minimal battery drain if the MBA was closed and sleeping for a similar period?
3) Or would it be equivalent to the even much smaller mini SoC drain from the MBA being actually shut down for that same 10-hour period?


There may not be significant difference in maintaining or replacing the SoC in the three scenarios above. My mind just wonders as a thought experiment how the process works. I always appreciate hearing from EE's or knowledgeable folks willing to explain in the weeds technical processes and theories. 🙂

 

[ArkSingularity]

1) Would the Apple 67W charger's charging profile or the Anker PIQ (PD+) 20W's charging profile with AlDente set at 75%, not actually send current to the battery in a 10-hour work period? Would both chargers just regulate their watt/voltage output to match the ≈ 7.5 watt normal use rate, and jump up to cover the very infrequent spikes to 9 or 10 watts?
2) Would whatever VERY minimal charging over say a 10-hour work period be about equivalent to making up for say the minimal battery drain if the MBA was closed and sleeping for a similar period?
3) Or would it be equivalent to the even much smaller mini SoC drain from the MBA being actually shut down for that same 10-hour period?


There may not be significant difference in maintaining or replacing the SoC in the three scenarios above. My mind just wonders as a thought experiment how the process works. I always appreciate hearing from EE's or knowledgeable folks willing to explain in the weeds technical processes and theories. 🙂

1) This is a great question. In the world of electronics, there's actually a little saying that states "power is drawn, not delivered". The power adapter actually isn't forcing 20 watts of power into the computer, it's just providing whatever the computer needs, up to 20 watts (or whatever the adapter is rated for). In very simplified terms, the computer just draws whatever it wants to use from the adapter, and if it isn't sufficient, it will pull the rest from the battery.

You might also be curious what would happen if the computer tried to draw too much power from the adapter. The Mac could try and it won't start a fire, but there would be a sudden voltage drop on the power adapter as soon as it couldn't deliver any more amps. This would force the laptop to draw the rest from the battery. Incidentally, batteries themselves have limits on how much current can be drawn too, which is why very old batteries sometimes can't keep up and result in sudden shutdowns on phones and computers.

If, on the other hand, the computer only needs 10 watts, it will only draw 10 watts from the adapter and won't draw any more (which would be wasted as heat if it were to be drawn anyway, which is why it's a very good thing that circuits don't do this!)

If Aldente is set up to not charge the computer, the Mac will only draw what it needs to run the computer and won't send any excess current to the battery unless it drops below the target battery charge. Aldente Free actually will automatically make minuscule adjustments and make sure to maintain that charge, so if the Mac has to pull any excess current from the battery, it would return that current later in minuscule charge amounts. Aldente Pro has an optional "sailing mode" feature that prevents this behavior if you desire it.

2 & 3) A little unsure on these. There are things besides just power drain to worry about as well, the battery management system has to keep up with self-discharge and things of that sort too (although self discharge for lithium ions is typically in the realm of a fraction of a percent per day). I'm not sure how this is handled under the hood, other than that I know that Apple widely uses Texas Instruments chips to do this (the datasheets on them might have more info). Someone else might be more qualified to discuss this sort of thing than I would.

 

[DavidChoux]

I would guess using a 10W charger in some cases would be more harmful than a higher wattage charger. If you're doing something a bit more intensive and the computer needs to draw more than 10W it'll pull the excess from the battery. So you might be going through a phases where the computer uses power from the charger, then battery, then charger etc. etc. and I can't imagine this is better for the battery than just using a higher wattage charger.

Other than that IIRC the best way to maintain battery health is to keep the battery away from >80% and <20% charge.

 

[Don MC]

Don,
Cool signature, dude. 😎
Any chance you can look up where you bought it and see if it listed as USB 2.0, 3.0, or 3.1.

On closer inspection, it is the charging cable that came with my Logitech MX Master 3 mouse. I suppose it's only for charging the mouse, so no USB3 or anything fancy like that.

 

[arcite]

What is the objective here? To somehow preserve the battery life a little longer? My MacBook Air has well over 1300 cycles....only around 1200 did I start getting warnings to replace soon. however, now the inevitable is taking hold, and it says replace now. I shan’t bother however, it’s hardly worth shelling out $200 to replace a battery in a nearly obsolete computer, instead I’ll be upgrading to a new MacBook shortly.

Long story short, Apple engineers know what they’re doing. Just use your laptop.

 

[DavidChoux]

Long story short, Apple engineers know what they’re doing. Just use your laptop.

They can't defy the behaviour of lithium ion cells though. They haven't magically been able to make them not degrade faster and high and low states of charge. It has to be botched with something like the 80% charge limit.

Engineers can only go so far lol, they're not magicians. I don't get a lot of people on here who say trust the Apple engineers for all of these things without actually thinking about it.

Anyway OP just wants to preserve battery life, let them be.

 

[CTHarrryH]

My M2 is kept plugged in 95% of the time since I bought it. It runs this built in program that doesn't charge to more than 80% with the statement this improves battery life. I can get it to 100% if I want.

 

[Technerd108]

Keeping an ion lithium battery plugged in all the time is not good no matter what type of charger.

It will reduce battery lifespan significantly. Better to use Apple built in battery optimization and charge to 80% and let it drain to 20%.

The battery is meant to be used. If you charge it only when it reaches 20% but not lower and let it charge to 80% and not higher and do this on a regular basis as you use it and as needed you will extend the battery lifespan as much as possible.

Batteries are consumable parts and will wear out no matter what you do.

Trickle charge or plugged in all the time won’t extend the lifespan.

As long as you use an apple charger it will automatically adjust as it charges giving a higher wattage at first and lowering as it nears the end of the charge. It has a smart charging system so you don’t need to interfere with it. Just use it as suggested above and you will have the longest possible battery lifespan.

 

[flyfly]

This is exactly what I want to avoid as much as possible. I'm trying to discern if keeping my MBA M2 plugged in through the work day to my current Apple 67W charger (or future Dell 6000 Dock 65W charge), has any negative effect on the battery or adds to battery cycles.

Today, the MBA has been plugged into the 67W charger for ≈ 6 hours or so up to now. It was at 23%, went to 100% where it has remained the whole time. It seems the 67W charger keeps battery topped off all day as I use VERY small amounts of power. How does this affect battery cycles? I really do not understand 'cycles' in this usage scenario. Is being plugged in all work day, unplugging from say 10pm to 9:00am 5 or so days a week, and unplugged days it is not in use the best way to extend my MBA's battery life? I plan to use this MBA M2 for hopefully ten years. My last MBA (mid 2013 13") was in part time use until I got the M2, so 9+ years. It was not my main machine. This M2 is taking over as my main machine from my late 2012 Mac Mini. (specs of current and retiring machines below).

same as my process! from 2013 MBA to the M2. I keep it plugged most of the time and it stays at 100%. I might unplug it until 95% and then i get it back to the charger. I did it this way on my 2013 MBA and battery lasted like 6 years pretty good.

 

[davekro]

Keeping an ion lithium battery plugged in all the time is not good no matter what type of charger.

It will reduce battery lifespan significantly. Better to use Apple built in battery optimization and charge to 80% and let it drain to 20%.

The battery is meant to be used. If you charge it only when it reaches 20% but not lower and let it charge to 80% and not higher and do this on a regular basis as you use it and as needed you will extend the battery lifespan as much as possible.

Batteries are consumable parts and will wear out no matter what you do.

Trickle charge or plugged in all the time won’t extend the lifespan.

As long as you use an apple charger it will automatically adjust as it charges giving a higher wattage at first and lowering as it nears the end of the charge. It has a smart charging system so you don’t need to interfere with it. Just use it as suggested above and you will have the longest possible battery lifespan.

I understand the point that it is healthy for Li-ion batteries to go through use cycles and best between 20% and 80% (75% is MY AlDente setting) SoC. To understand the electrical theory (okay, and to appease my OCD mind ;o), is it to any degree better for extending battery health into my planned year ten M2 use, to lower the frequency, and hence lower annual number of 75-20-75-20%…charge cycles from 5 times per week to 1 time per week? For example:
1) If leaving my M2 unplugged until it dropped to 20% SoC an average of 5 times per week, and I recharged to 80% each time.
-OR-
2) If I keep the M2 plugged-in ~ 60% of the time each day (at trickle charge maintaining at 75% SoC), then putting it to sleep and unplugging at bed time. Once per week let discharge to 20%. Balance of week, 60% plugged in, 40% (while asleep at night) per day.

I realize this may be more of an academic question because there is not a significant difference if at year 9 the battery is at 70% vs 80% OEM aH capacity. But if at year 9 the potential might be between 60% vs 80%, that is significant. Just for me, I would adjust my plug-in plan for the possibility of having 10% better battery capacity at year 9. This question certainly does not affect the vast majority of MacBook owners who would retire their MB’s, at least from primary use, way before their battery capacity was an issue. But for people planning to use until end of life, it is a pertinent question.
Thanks for any insights into this question.

 

[trevpimp]

I charge my M1 MBA when it goes down to 50% then I fully charge it to 100% I don’t get below 50%

Honestly there are so many ways to try and protect your battery but to me it’s just a better option to take care of your Mac.

- Don’t leave it in too hot/cold weathers (could damage internals)
- Don’t leave near metals/ magnets/ (^)
- Don’t use near or around liquids
- Keep it in a case when not in use
- Take care of the battery by not letting it go down below 50%

 

[ArkSingularity]

I charge my M1 MBA when it goes down to 50% then I fully charge it to 100% I don’t get below 50%

Honestly there are so many ways to try and protect your battery but to me it’s just a better option to take care of your Mac.

- Don’t leave it in too hot/cold weathers (could damage internals)
- Don’t leave near metals/ magnets/ (^)
- Don’t use near or around liquids
- Keep it in a case when not in use
- Take care of the battery by not letting it go down below 50%

Charging fully to 100% is actually one of the worst things you can do if you're trying to maximize battery cycle life. Some tests have more than tripled the number of cycles that Lithium Batteries can withstand by doing nothing else other than limiting the charge to 80%.

Lithium ion batteries are also charged to around 40% to 50% on purpose before placing them in storage (or shipping them in a device) because this is the state-of-charge that is chemically the least damaging to the battery. If anything, you want to keep it closer to this state of charge to maximize the battery's longevity.

 

[jdb8167]

Charging fully to 100% is actually one of the worst things you can do if you're trying to maximize battery cycle life.

Apple seems to think that charging to 100% isn’t as bad as leaving it at 100%. Of course Apple might have a slight interest in battery replacements. But they charge to 100% just before they think you are going to use the MacBook on battery.

 

[ArkSingularity]

Apple seems to think that charging to 100% isn’t as bad as leaving it at 100%. Of course Apple might have a slight interest in battery replacements. But they charge to 100% just before they think you are going to use the MacBook on battery.

Well, there are two kinds of aging that they have to worry about: Cycle aging and calendar aging. Cycle aging measures the battery's health as it is repeatedly charged and discharged, but lithium batteries will lose capacity just sitting on a shelf too. The rate at which this happens is mostly a function of temperature and the state of charge that it is stored at.

Some of the more recent studies they have performed have shown that lithium batteries generally lose about 20% of their health/capacity in just one year sitting on a shelf if stored at 100% charge. At 80% charge, they lost only about 4%. It's a pretty dramatic difference, and is part of why Apple doesn't like to keep the battery at 100% any longer than it has to.

In other words, charging to 100% is more stressful on the battery than charging it to a lower percentage (such as 80%), but keeping it at 100% is far worse, as it also significantly accelerates calendar aging.

 

[davekro]

In other words, charging to 100% is more stressful on the battery than charging it to a lower percentage (such as 80%), but keeping it at 100% is far worse, as it also significantly accelerates calendar aging.

AlDente or similar 3rd party app seems like a mandatory one to limit maximum charge capacity. My Samsung S21 phone has a setting for 85% max charge. I wonder why Apple does not have a setting choice like that for it’s laptops?