Battery service recommend but what's the issue?

Batteries are considered Consumable Products. Over time it will degrade to a point where it needs to be replaced. The usage is normal as the capacity will go up and down all the time and never stay always at 100%. Apple Batteries are rated for 1000 Full Battery Cycles and / or 80% Capacity before needing Evaluation or replacement.

There is nothing difficult to understand - the battery can not or is not suppling Reliable Power to the computer. This results in sudden shutdown which in turn negatively affect the other components of the machine as well as the OS - corruption may occur

Make a Time Machine Backup ASAP and if possible a Bootable Clone to two each to separate external Drives.

Find an Apple Authorized Service Provider nearest your location. Fill in to Country and City in the website

Inside all batteries you have an anode, cathode, separator, electrolyte and two current collectors ( + / - ) terminals. All batteries rely upon the chemical reaction of these materials to hold an electrical charge and to delivery that charge. The chemistry of all these things varies in different battery designs. Over time, the electrolyte will eventually cause corrosion on the anode and that corrosion will cause battery cells to stop holding a charge as well. Battery technology is always evolving and the chemistry is altered as well as the design of the cells and different materials last longer before this corrosion occurs but all batteries will encounter corrosion eventually. There are some brand new designs in the early development stages that will offer batteries that last years longer in the future.

Within the 30% of your battery capacity, portions of the cells are shorting out due to anode corrosion and unable to provide a consistent amount of amperage. You can think of amperage like the flow of water through a pipe. Except it's the flow of electrons. Imagine a water wheel being spun by the flow of water. If the flow of the water or the pressure drops then the wheel will stop spinning. The pipe carrying the water is corroded inside and less water can flow. The battery cells that form the first 30% of your battery have corroded anodes. When the charge runs down to those battery cells within the 30% mark, they no longer hold a charge or simply cannot provide enough amperage flow and suddenly your Mac turns off abruptly. If this continues, that 30% will increase till the battery won't hold a charge at all. This happens to all batteries. The batteries in an electric car are no different. The range will be reduced and the ability to quick charge will fail.

Apple has made considerable strides in providing good information to the users of their products about the health of the battery. They are also taking steps to help extend the lifespan of a battery. In iPhones, when you charge them at night, it will charge up to 80% then wait till an hour before you wake to trickle charge the remaining 20% up to 100% charged. They do this because it helps extend the lifespan of the battery. New Apple Silicon M1 Macs work in a similar fashion, pausing the charging at times to extend the battery lifespan. In iPhones and Macs you will be alerted when the health of your battery has degraded. Which explains the message you are seeing.

Unfortunately, your battery is degraded and needs to be replaced. The battery is designed to last under normal average usage patterns between 3-7 years, the typical lifespan of most all laptop computers. Environmental (heat / cold) and usage patterns can age a battery faster than the estimated lifespan. If your Mac is new and your battery fails, Apple will replace it under warranty (AppleCare). If it is out of warranty, $129 for a 13-inch MacBook Air. If it's a very old Mac, Apple or Apple Authorized repair centers may refuse to service it. There are plenty of other repair shops that will service vintage Macs allowing you to use it for a few more years.

As @steve626 mentioned, he was able to have a 3rd party repair center replace his 8 year old 13-inch MacBook Air battery for less than what Apple charges (Apple may have refused to service it) and ended up with a longer lasting charge that exceeds the original battery.

Some links from Apple:

https://support.apple.com/mac/repair/service

https://support.apple.com/en-us/HT204054

https://support.apple.com/en-us/HT212049

It's not functioning properly. It's is suddenly unable to support Mac operations when below 30%. It should work down to 1%. You probably have one or more bad cells in the battery. It is rated for 1000 cycles, you have nearly 800, that's not an absolute guaranty, however; there are other factors that affect battery life. It's like automobile tires rated for 60,000 miles, sometimes you get a bit less because of the road conditions, environmental factors, uneven wear. Or the battery may have a defect. Either way, it needs to be replaced.

I recently replaced a battery in a (2013) 13-inch Macbook Air. The new battery was $69 from OWC and the shop that replaced it for me charged $35. The new battery has much higher capacity than the original one did, which is a bonus.

What specific model is it?

MacBook Air (Retina, 13-inch, 2018)

MacBookAir8,1

Model: A1932

If you still have AppleCare then contact Apple. It would be $129 out of warranty to replace the battery via Apple and a bit less via. 3rd party.

No the software might not be accurately reporting the details from the battery. But it's not going to cause your battery to fail sooner than it should. You have a message from macOS saying your battery is degraded and it powers off at 30% so that means the battery is worn out.

The new M1 MacBook Air does handle battery lifespan extension measures far more aggressively and the M1 draws far less power. You should see real world 15 hours of battery out of the new Air. It would also be considerably faster at most everything.

It's your call if you wish to upgrade to an M1 now or replace the battery and go a few more years. Most businesses replace laptops every 3-5 years like clockwork. If you replace the battery you are likely to get close to 4 more years of use before it's obsolete. Maybe a bit sooner due to the Apple Silicon transition away from Intel.

James Brickley's comments make a lot of sense to me.

Your Al Dente software sounds like a good way to try to prolong battery life. Starting with Catalina and Big Sur, Apple MacOS started more actively managing the charging behavior to try to prolong battery life, in ways similar but not identical to Al Dente.

Batteries are variable. We have a 2010 Macbook Air used constantly, plugged in to charger most of the time, the battery has had several hundred cycles and shows 85% capacity ("healthy").

The 2013 Macbook Air was used the same way as the 2010 but its battery wore out completely and was replaced.

My work laptop is replaced by my employer every 3 years, due to things like batteries, SSD's, etc. tending to show signs of wearing out then. My work Macbook Pro was just replaced with a new one. After 3 years its battery was down to about 80% capacity ("healthy") with 300 cycles but the battery had swollen so much the laptop could not be closed all the way and the keyboard was sometimes not typing properly.

So batteries vary a lot. I would not replace a laptop that was otherwise working well just due to a battery wearing out. That 2013 laptop I have is still very peppy and runs fine. It's on Catalina but can go to Big Sur.

Batteries tend to do better when they aren't constantly charging and at 100%. That's why there are programs like Al Dente and Apple has its battery health management. But our 2010 Macbook Air is still chugging away and its battery is "good" even though it's been connected to a charger most of the time. It's really quite variable.

@ James B. - Excellent and details explanation. +1

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