MacBook charging myths: what really wears the battery

Most MacBook charging worries are left over from older batteries and older laptops. A modern MacBook manages its own charging: it stops when the battery is full, and on Macs that offer Optimized Battery Charging it can hold the charge at 80 percent until it expects you to need the rest. Leaving it plugged in, charging overnight and using it while it charges are all fine.

What actually wears a battery is time, use and heat. You can't avoid the first two, and you shouldn't try to. Heat is the one worth your attention. Here are the common myths, one at a time, with what is true in each.

What really wears a battery

Every lithium-ion battery slowly loses capacity, however carefully it is treated. Apple says as much in the Battery section of System Settings: Mac batteries, like all rechargeable batteries, "are consumable components that become less effective as they age."

Three things drive that wear:

• Charge cycles. Each cycle is one battery's worth of energy used, whether in one sitting or across several days of top-ups. More cycles mean more wear, slowly.
• Age. Batteries lose capacity over the years even with light use.
• Heat, and long stretches at full charge. A battery that sits hot, or sits full for long periods, ages faster. This is the part your habits and your Mac's settings can actually change.

Keep that list in mind and most of the myths sort themselves out.

Myth: leaving it plugged in ruins the battery

For a modern MacBook, this one is mostly false. When the battery is full, the Mac stops charging it and runs from the adapter. It does not keep pushing power into a full battery.

The small grain of truth is that sitting at full charge all day adds some wear over time, especially if the Mac runs warm. That is what Optimized Battery Charging is for. The Mac learns when you usually unplug, holds the charge at 80 percent through the long plugged-in stretch, and tops up the rest in time for you to leave.

To check it is on:

1. Open System Settings > Battery.
2. Click the info button next to Battery Health.
3. Make sure Optimized Battery Charging is turned on.

When it is holding the charge, the battery menu in the menu bar may say charging is on hold. If you know you need a full battery today, you can usually choose to charge to full from that menu. If you turn the feature off, macOS offers to turn it off only until tomorrow, which is handy before a long trip.

Exactly what you see depends on your Mac. Some older models show a battery health management setting instead, which aims at the same thing in a different way. If neither appears, your Mac doesn't offer it, and the rest of the advice here still applies.

Myth: charging overnight is bad for it

Also mostly false, for the same reasons. The Mac stops charging when it is full, and if you charge overnight most nights, Optimized Battery Charging is built for exactly that routine: it can wait at 80 percent and finish charging closer to the time you usually unplug.

The real overnight risk is heat, not time. A MacBook charging on a bed, under a pillow or wrapped in a duvet can't get rid of heat the way it can on a desk or table. Charge it on a hard, open surface and overnight charging is nothing to worry about.

Myth: drain it fully to calibrate the battery

This was real advice once, for older laptops. For current MacBooks with built-in batteries, Apple doesn't ask you to do it, and running the battery to empty on purpose just adds a cycle of wear for nothing.

If the percentage sometimes jumps, for example from a moderate level to the low battery warning faster than you expect, that can be macOS refining its estimate, and it often settles with normal use. It can also be a sign of an aging battery, which Battery Health will show. A Mac that switches itself off with plenty of charge apparently left has a different problem, not a calibration one. Check Battery Health in System Settings > Battery, and if it says service is recommended, talk to Apple or an authorized service provider. MacBook battery health explained covers what each reading means.

For the everyday side of this, when to plug in and what to do when the charge runs low, see low battery on a MacBook.

Myth: any other charger will damage your Mac

Mostly false, as long as the charger is a decent one. MacBooks that charge over USB-C agree on power with the charger before drawing it, so a well-made USB-C charger from a reputable maker works safely.

A few things are worth knowing:

• A higher-wattage charger is fine. The Mac only draws what it needs.
• A lower-wattage charger is slower. It may charge the Mac only while it sleeps, or barely keep up when you are working hard. A phone charger falls in this group: it works, slowly.
• Cheap, unbranded chargers and damaged cables are the real risk. They are more likely to overheat or fail. If a charger or cable gets hot, smells or has frayed insulation, stop using it.
• MagSafe isn't the only way in. On recent MacBooks with a MagSafe port, the USB-C ports can usually charge the Mac as well.

To see which charger is connected and its wattage, hold Option, click the Apple menu, choose System Information and click Power. Look for AC Charger Information.

Myth: don't use it while it charges

False. Using a MacBook while it charges is normal and expected. The only caution is the same one again: heavy work, like exporting video or a long game, makes the Mac warm, and charging adds a little warmth of its own. Keep the vents and base clear and it is fine.

The short version

Where Notchpals fits

Notchpals doesn't manage charging or count cycles. macOS already does the clever part. What the Tech care character in your crew, Juice or Gumdrop, does is speak up at the one moment that matters day to day: when the battery drops below 20 percent and the Mac isn't charging, and again with more urgency below 8 percent. When you plug in after one of those warnings, it pops back once to celebrate.

JuiceResurrected! You saved me! I'll name my next bar after you.

Apart from that one cheer, it says nothing about the battery while the Mac is charging or full, so it won't nag you to unplug or tell you to drain it, both of which this post has just argued against. Juice is dramatic about all of it. The advice underneath is not: plug in when it is low, keep the Mac cool, and leave the top end of the charge to macOS.