How the iPhone battery works and how to manage its condition

What you need to know about iPhone batteries


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Your iPhone uses a lithium-ion battery that wears out over time, but there's little reason to worry about battery health in a new device. Here's what you need to know about your iPhone's battery.

Batteries are not mysterious black boxes that power your iPhone. In fact, they're pretty basic products compared to the advanced silicon they're powered by. The physical nature of batteries means they eventually wear out and become less useful over time, but device owners have nothing to worry about.

A little understanding of battery science can go a long way towards intelligently managing your device's lifespan. The iPhone controversy surrounding planned obsolescence and expected refresh cycles can easily be dismissed as an overstatement with some knowledge.

Lithiumion battery basics

The battery consists of an anode (+) and a cathode (-), separated, as a rule, by a combustible electrolyte. When the device is powered by a battery, charged lithium ions travel from the anode to the cathode through the electrolyte, releasing electrons.

These released electrons power the device and return to the cathode, creating a complete electrical circuit. When charging the device, the opposite happens — electrons pass through the anode and move towards the cathode.

Without getting too technical, these two chemical reactions are imperfect and result in heat loss and battery wear. The lithium material is slowly depleted, oxidation reduces usable surface area, and filaments grow out of the battery plates. All this leads to the degradation of the cells and, ultimately, to the discharge of the battery.

Slim phones mean smaller batteries that drain faster

There is nothing the user can do to completely stop this process. Just like using gasoline to fill up a car, it eventually runs out. However, discharging a lithium battery takes a long time and can be somewhat mitigated by user and software behavior.

So when a new iPhone has 100 percent battery, it has all the milliamp-hour rating available when fully charged. This also means that the battery can provide sufficient processor power during peak current draw without any problems.

Apple says its batteries are rated to retain up to 80% of their original capacity with 500 full charge cycles. The charge cycle is defined as a full discharge of the battery to zero, followed by a full charge to 100%.

Top: Description of the fast charge cycle. Bottom: An explanation of the charge cycle. Image courtesy of Apple

Expected battery life may vary from user to user. The average user is expected to keep the battery above 80% for the first two years with regular use.

Others who use their iPhone constantly and charge their device almost to 100% several times a day will notice that their battery drains faster.

Ultimately, as soon as the battery is discharged below 80% of its original capacity, protections in the operating system are activated to ensure that the device does not turn off unintentionally. This throttling can be avoided by having the battery replaced by an Apple Authorized Service Provider.

After iPhone disables the processor for the first time, a new toggle will appear in battery settings to prevent shutdown. This gives users the option to disable the throttling feature and allows the processor to draw full current.

However, the device will turn off as soon as the current drawn exceeds what the battery can provide. Disabling the throttling feature is strongly discouraged as this may damage the battery.

Old Batteries

Prior to the release of iOS 10.2.1 in 2017, the iPhone did little to account for battery aging in its software. However, a perfect set of circumstances led Apple to complain about inadvertent shutdowns on older devices.

Recent devices have had more powerful processors, thinner designs, and brighter displays. These factors caused smaller batteries with lower capacity to run out faster. A smaller battery also meant lower peak voltage, which meant that aging batteries dropped below their peak voltage rating more quickly.

These factors were linked to more people than ever buying iPhones and then keeping them for longer than expected, leading to more reports of battery drain. Please note that the Plus and iPad models did not experience shutdown issues due to the larger battery capacity.

Lithium-ion cannot provide peak voltage at lower charges, which worsens with age

Intermittent blackouts have been reported by iPhone 6s, iPhone 6s and iPhone SE owners. Users complained that the device showed a battery level of 30% or more, and then suddenly turned off, as if the battery was dead.

This was due to the fact that the batteries of these devices were drained to the point where they could no longer provide peak power during peak CPU usage. Since there were no other protections, the iPhone sensed that the processor's power draw exceeded the available current and simply shut down to protect the battery.

In iOS 10.2.1 and later updates, security measures have been introduced that limit CPU usage based on the remaining battery power of the device. Newer batteries above 80% health will never experience this CPU throttling feature.

Apple did not think about such a need until massive outage reports began.

iPhone 6 and iPhone SE suffered unintentional shutdown due to aging batteries

Apple has never publicly announced measures to protect the battery, instead it has included a footnote in a software update security and stopped there. Later, users began noticing that their devices were slowing down, blaming planned obsolescence and other conspiracies until Apple issued a statement.

Lawsuits have begun, and Apple has issued a public apology for the feature, saying it was always meant to extend the life of devices, not to force users to upgrade early. Newer iPhones since the iPhone X have also had much larger batteries, meaning the battery takes much longer to drain after peak current draw.

The CPU throttling function protects the batteries from overcurrent, which can lead to overheating or even fire. This feature is not intended to encourage users to upgrade their phones, despite what some YouTubers may tell you.

Battery health management doesn't have to be a full-time job

There is a lot of discussion about battery conservation and how users should charge their devices. Some say that any wireless charging should be avoided for the best battery health, but that's not all.

Due to the multitude of wireless chargers, our iPhone is constantly charging, which is normal

Battery chemistry varies with heat, charging speed, and environment. In an ideal world, the longest battery life a human can achieve would be achieved if the room temperature was constantly at 65 degrees, the iPhone was only charged via wire from 20% to 80% at about 10W, and the processor was never charged. heated up during use.

This fantasy scenario is impractical, if not impossible, for many reasons. Also, the theoretical gain in battery health will never equal the performance associated with maximizing battery life.

So Apple has implemented several tools, invisible to the user, to make sure battery life is extended for as long as practical. For example, a dedicated power management processor provides power management for optimal charging speeds at all times.

The iPhone will also learn your charging habits and, based on that, adjust how it charges the device. So it can quickly charge up to 80% once plugged in, but then it will keep the battery charged until it gets close to your daily wake up time before charging the battery to 100%.

These built-in systems help protect your iPhone battery and can work much more efficiently than human intervention. So users only have to decide how and when to charge their iPhone and leave the rest up to the power management software.

Choosing charging method: wired or wireless Wireless

Your iPhone can be charged with a Lightning cable, MagSafe puck, and Qi wireless charging cradle. Each of these three methods has its own advantages and disadvantages.

Wired iPhone charging

Wired charging is the fastest and most efficient way to get power from your devices. For example, the iPhone 13 consumes about 22W, and the iPhone 13 Pro Max can even support about 27W charging for half an hour.

iPhone starts “fast charging” when using an 18W or higher adapter that supports Power Delivery. This feature can allow any iPhone 8 or newer to reach 50% capacity in about 30 minutes. Fast charging iPhone 12 and later requires a 20W charging adapter or higher.

This 65W adapter can quickly charge two connected iPhones with its high power

Wired connections are the most efficient because the electrical conductors physically touch. Energy is transferred through the wire through conductive surfaces with maximum efficiency and minimum heat loss.

However, faster charging means more heat, more heat loss, and overall less efficiency. Users who rely heavily on fast charging will drain their battery faster.

Wall chargers are getting more power for less money, especially since the advent of GaN. Thus, there is a good chance that iPhones will be connected to fast chargers more regularly.

The iPhone controls the rate of charging even when connected to a fast charger, so the battery is not charged at full capacity all the time. However, fast charging is a tool, so only use it as needed. We'll look at charging recommendations later.

Convenience always comes at the expense of some aspect, and in this case, faster charging means faster electrode wear. The convenience factor also applies to wireless charging.

Qi wireless and Charging iPhone with MagSafe

Wireless charging is a very convenient charging method that allows users to place their iPhones on a surface to start charging. MagSafe goes one step further by attaching iPhone to a magnet and increasing the speed and efficiency of charging.

Wireless charging uses coils separated by a small air gap to transfer power from one set of coils to another. Efficiency and speed increase as the coils get closer to each other, so MagSafe magnetic alignment makes the job much more efficient.

MagSafe is a more efficient form of wireless charging

iPhone will charge up to 7.5W on the wireless charging pad, while MagSafe provides up to 15W. Standard Qi wireless charging is not only slower, but also much less efficient and in some cases can heat up the iPhone more than MagSafe.

The air gap between the coils, however small, poses serious efficiency problems. When electricity passes through the charging coils, it generates a magnetic field that interacts with the coils in the iPhone to charge the battery. This magnetic field is inherently inefficient since most of the field is lost in empty air.

Spiral wire laid close together with electricity running through it gets very hot, so wireless charging pads tend to be warm surfaces. The coils in the iPhone also heat up during power transfer, creating another source of heat. In general, wireless charging is a very warm process that can affect battery chemistry in the long run.

Qi chargers exacerbate these problems due to poor customization and the manufacturer's tendency to use cheaper parts. Just because an iPhone starts charging after being placed on a Qi charger doesn't mean the coils are perfectly aligned, which increases heat loss and reduces charging speed. More heat means the battery drains faster, as we've already discussed.

MagSafe is a more efficient form of wireless charging

MagSafe addresses some of these issues through higher material standards as well as magnetic alignment. Some chargers take advantage of MagSafe magnets, offering only 7.5W Qi charging speeds, which is a decent average. However, customers should look for true 15W MagSafe chargers whenever possible to ensure the best possible charging experience and efficiency.

Note that MagSafe chargers are still admittedly not very efficient, and users need to have 20W Power Delivery Power Adapters to achieve 15W wireless charging. Power adapters without the appropriate specifications will only charge the iPhone at 7.5W.

The iPhone adjusts its charging speed to manage heat, or even stops wireless charging if it gets too hot by 80%. Using wireless charging in cool environments provides the best performance.

Charging recommendations

The most important rule for charging your iPhone is planning ahead. Have your chargers where you need them, know what they are for, and know when to use them best. This level of understanding shouldn't take much time or effort beyond the initial setup.

Your battery will chemically discharge over time and this cannot be avoided. On average, iPhone users can expect battery health to decline by about 10% per year depending on the factors described above.

What can be adjusted is the rate of battery damage. The best way to do this with the least effort is to trust battery management software and use some basic guidelines.

For example, don't expose your iPhone to direct sunlight or expose it to extreme heat when using a car air vent mount. Never leave your iPhone in a car in the summer and be sure to keep it away from hot surfaces.

Don't let your iPhone battery drain completely, but also try to avoid unnecessary charging. If you're going away for a few hours, connecting your iPhone to a fast charger is a great way to recharge your battery while you get ready.

Battery health will degrade over time, no matter how you manage charging

Overnight charging is also perfectly safe, as the iPhone will control the charging rate based on your normal charging mode. sleep schedule. A less than 18W wired charger by the bed will provide the best battery health, but overnight MagSafe or Qi charging isn't too bad either.

If you're really worried about battery health, prefer wired slow charging first, then fast charging, then MagSafe, and possibly avoid or minimize Qi charging. Of course, all charging methods available are safe, they may just result in you needing a new battery a month or two before the expected two year window.

For most people, it's just better to keep your iPhone charged and not worry too much about battery health. If you intend to keep the device for yourself or give it to someone to use it for more than two years, expect to get a replacement battery for $69.

No combat chemistry or physics.

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