Control and limit battery charging on Apple Silicon MacBooks.
GPL-2.0 License
👆↖️ Note: use table of contents of quickly navigate to the section you want.
batt
is a tool to control battery charging on Apple Silicon MacBooks.
This article might be helpful. TL;DR: keep your battery at 80% or lower when plugged in, and discharge it as shallowly as feasible.
Previously, before optimized battery charging is introduced, MacBooks are known to suffer from battery swelling when they are kept at 100% all the time, especially the 2015s. Even with optimized battery charging, the effect is not optimal (described below).
batt
can effectively alleviate this problem by limiting the battery charge level. It can be used to set a maximum charge level. For example, you can set it to 80%, and it will stop charging when the battery reaches 80%. Once it reaches the predefined level, your computer will use power from the wall only, leaving no strain on your battery.
Quick link to installation guide.
batt
tried to keep as simple as possible. Charging limiting is the only thing to care about for most users:
However, if you are nerdy and want to dive into the details, it does have some advanced features for the computer nerds out there :)
It is free and opensource. It even comes with some features (like idle sleep preventions and pre-sleep stop charging) that are only available in paid counterparts. It comes with no ads, no tracking, no telemetry, no analytics, no bullshit. It is open source, so you can read the code and verify that it does what it says it does.
It is simple but well-thought. It only does charge limiting and does it well. For example, when using other free/unpaid tools, your MacBook will sometimes charge to 100% during sleep even if you set the limit to, like, 60%. batt
have taken these edge cases into consideration and will behave as intended (in case you do encounter problems, please raise an issue so that we can solve it). Other features is intentionally limited to keep it simple. If you want some additional features, feel free to raise an issue, then we can discuss this.
It is light-weight. As a command-line tool, it is light-weight by design. No electron GUIs hogging your system resources. However, a native GUI that sits in the menubar is a good addition.
Yes, macOS have optimized battery charging. It will try to find out your charging and working schedule and prohibits charging above 80% for a couple of hours overnight. However, if you have an un-regular schedule, this will simply not work. Also, you lose predictability (which I value a lot) about your computer's behavior, i.e., by letting macOS decide for you, you, the one who knows your schedule the best, cannot control when to charge or when not to charge.
batt
can make sure your computer does exactly what you want. You can set a maximum charge level, and it will stop charging when the battery reaches that level. Therefore, it is recommended to disable macOS's optimized charging when using batt
.
Currently, it is command-line only. Some knowledge of the command-line is recommended. A native GUI is possible but not planned. If you want to build a GUI, you can ask me to put a link here to your project
bash <(curl -fsSL https://github.com/charlie0129/batt/raw/master/hack/install.sh)
. You may need to provide your password (to control charging). This will download and install the latest stable version for you, then you can skip to step 5.chmod +x batt
after extracting the archive) or build it yourself .$PATH
, e.g., /usr/local/bin
, so you can directly call batt
on the command-line. In this case, the binary location will be /usr/local/bin/batt
.sudo batt install
. If you do not want to use sudo
every time after installation, add the --allow-non-root-access
flag: sudo batt install --allow-non-root-access
. To uninstall: please refer to How to uninstall?
sudo spctl --master-disable
to disable GateKeeper entirely.sudo batt status
. If you see some status info, you are good to go!batt
will set a charge limit to 60%. For example, to set the charge limit to 80%, run sudo batt limit 80
.batt
. To do so, open System Preferences, go to Battery, and uncheck Optimized battery charging.Notes:
batt help
to see all available commands. To see help for a specific command, run batt help <command>
.sudo batt limit 100
.Finally, if you find
batt
helpful, stars ⭐️ are much appreciated!
Make sure your computer doesn't charge beyond what you said.
Setting the limit to 10-99 will enable the battery charge limit, limiting the maximum charge to somewhere around your setting. However, setting the limit to 100 will disable the battery charge limit. If you want to charge your MacBook to 100% or revert any changes, you can simply set the limit to 100%.
By default, batt
will set a 60% charge limit.
To customize charge limit, see batt limit
. For example,to set the limit to 80%, run sudo batt limit 80
. To disable the limit, run sudo batt limit 100
.
Cut or restore power from the wall. This has the same effect as unplugging/plugging the power adapter, even if the adapter is physically plugged in.
This is useful when you want to use your battery to lower the battery charge, but you don't want to unplug the power adapter.
To enable/disable power adapter, see batt adapter
. For example, to disable the power adapter, run sudo batt adapter disable
. To enable the power adapter, run sudo batt adapter enable
.
Check the current config, battery status, and charging status.
To do so, run sudo batt status
.
These advanced features are not for most users. Using the default setting for these options should work the best.
Set whether to prevent idle sleep during a charging session.
Due to macOS limitations, batt
will pause when your computer goes to sleep. As a result, when you are in a charging session and your computer goes to sleep, the battery charge limit will no longer function and the battery will charge to 100%. If you want the battery to stay below the charge limit, this behavior is probably not what you want. This option, together with disable-charging-pre-sleep, will prevent this from happening.
To prevent this, you can set batt
to prevent idle sleep. This will prevent your computer from idle sleep while in a charging session. This will only prevent idle sleep, when 1) charging is active 2) battery charge limit is enabled. So your computer can go to sleep as soon as a charging session is over.
However, this does not prevent manual sleep. For example, if you manually put your computer to sleep or close the lid, batt
will not prevent your computer from sleeping. This is a limitation of macOS. To prevent such cases, see disable-charging-pre-sleep.
To enable this feature, run sudo batt prevent-idle-sleep enable
. To disable, run sudo batt prevent-idle-sleep disable
.
Set whether to disable charging before sleep if charge limit is enabled.
Due to macOS limitations, batt
will pause when your computer goes to sleep. As a result, when you are in a charging session and your computer goes to sleep, the battery charge limit will no longer function and the battery will charge to 100%. If you want the battery to stay below the charge limit, this behavior is probably not what you want. This option, together with prevent-idle-sleep, will prevent this from happening. prevent-idle-sleep can prevent idle sleep to keep the battery charge limit active. However, this does not prevent manual sleep. For example, if you manually put your computer to sleep or close the lid, batt will not prevent your computer from sleeping. This is a limitation of macOS.
To prevent such cases, you can use disable-charging-pre-sleep. This will disable charging just before your computer goes to sleep, preventing it from charging beyond the predefined limit. Once it wakes up, batt
can take over and continue to do the rest work. It will only disable charging before sleep if battery charge limit is enabled.
To enable this feature, run sudo batt disable-charging-pre-sleep enable
. To disable, run sudo batt disable-charging-pre-sleep disable
.
When you set a charge limit, for example, on a Lenovo ThinkPad, you can set two percentages. The first one is the upper limit, and the second one is the lower limit. When the battery charge is above the upper limit, the computer will stop charging. When the battery charge is below the lower limit, the computer will start charging. If the battery charge is between the two limits, the computer will keep whatever charging state it is in.
batt
have similar features built-in (since v0.1.0
). The charge limit you have set (using batt limit
) will be used as the upper limit. By default, The lower limit will be set to 2% less than the upper limit. Same as using 'batt lower-limit-delta 2'. To customize the lower limit, use batt lower-limit-delta
.
For example, if you want to set the lower limit to be 5% less than the upper limit, run sudo batt lower-limit-delta 5
. So, if you have your charge (upper) limit set to 60%, the lower limit will be 55%.
Only available after (not including)
v0.1.0
. It is disabled by default.Acknowledgement: @exidler
This setting can make the MagSafe LED behave like a normal device, i.e., it will turn green when charge limit is reached (not charging). By default, on a MagSafe-compatible device, the MagSafe LED will always be orange (charging) even if charge limit is reached and charging is disabled by batt, due to Apple's limitations. You cannot enable this feature on a non-MagSafe-compatible device.
One thing to note: this option is purely cosmetic. batt will still function even if you disable this option.
To enable MagSafe LED control, run sudo batt magsafe-led enable
.
Logs are directed to /tmp/batt.log
. If something goes wrong, you can check the logs to see what happened. Or raise an issue with the logs attached, so we can debug together.
You need to install command line developer tools (by running xcode-select --install
) and Go (follow the official instructions here).
Simply running make
in this repo should build the binary into ./bin/batt
. You can then follow the upgrade guide to install it (you just use the binary you have built, not downloading a new one, of course).
You can think of batt
like docker
. It has a daemon that runs in the background, and a client that communicates with the daemon. They communicate through unix domain socket as a way of IPC. The daemon does the actual heavy-lifting, and is responsible for controlling battery charging. The client is responsible for sending users' requirements to the daemon.
For example, when you run sudo batt limit 80
, the client will send the requirement to the daemon, and the daemon will do its job to keep the charge limit to 80%.
I created this tool simply because I am not satisfied with existing tools 😐.
I have written and using similar utils (to limit charging) on Intel MacBooks for years. Just since recently, I got hands on an Apple Silicon MacBook (yes, it is 2023, 2 years later since it is introduced 😅 and I just got one). The old BCLM way to limit charging doesn't work anymore. I was looking for a tool to limit charging on M1 MacBooks.
I have tried some alternatives, both closed source and open source, but I kept none of them. Some paid alternatives' licensing options are just too limited 🤔, a bit bloated, require periodic Internet connection (hmm?) and are closed source. It doesn't seem a good option for me. Some open source alternatives just don't handle edge cases well and I encountered issues sometimes especially when sleeping (as of Apr 2023).
I want a simple tool that does just one thing, and does it well -- limiting charging, just like the Unix philosophy. It seems I don't have any options but to develop by myself. So I spent a weekend developing this tool, so here we are! batt
is here!
sudo batt uninstall
to remove the daemon.sudo rm /etc/batt.json
.batt
binary itself by sudo rm $(where batt)
.Automatic:
Updates to the latest stable version. If you want to use other versions (beta, development), please use the manual method.
bash <(curl -fsSL https://github.com/charlie0129/batt/raw/master/hack/install.sh)
Manual:
sudo batt uninstall
to remove the old daemon.chmod +x batt
after extracting the archive) or build it yourself .batt
binary with the downloaded new one. sudo cp ./batt $(where batt)
sudo batt install
to install the daemon again. Although most config is preserved, some security related config is intentionally reset during re-installation. For example, if you used --allow-non-root-access
when installing previously, you will need to use it again like this sudo batt install --allow-non-root-access
.You probably don't need this on Intel :p
On Intel MacBooks, you can control battery charging in a much, much easier way, simply setting the BCLM
key in Apple SMC to the limit you need, and you are all done. There are many tools available. For example, you can use smc-command to set SMC keys. Of course, you will lose some advanced features like upper and lower limit.
However, on Apple Silicon, the way how charging is controlled changed. There is no such key. Therefore, we have to use a much more complicated way to achieve the same goal, and handle more edge cases, hence batt
.
Probably not. batt
was made Apple-Silicon-only after some early development. I have tested batt on Intel during development (you can probably find some traces from the code :). Even though some features in batt are known to work on Intel, some are not. Development and testing on Intel requires additional effort, especially those feature that are not working. Considering the fact that Intel MacBooks are going to be obsolete in a few years and some similar tools already exist (without some advanced features), I don't think it is worth the effort. If you are interested in developing an Intel version, feel free to raise a PR.
TL,DR; This is intended, and is the default behavior. It is described here. You can turn this feature off by running sudo batt disable-charging-pre-sleep disable
(not recommended, keep reading).
But it is suggested to keep the default behavior to make your charge limit work as intended. Why? Because when you close the lid, your MacBook will go into forced sleep, and batt
will be paused by macOS. As a result, batt
can no longer control battery charging. It will be whatever state it was before you close the lid. This is the problem. Let's say, if you close the lid when your MacBook is charging, since batt
is paused by macOS, it will keep charging, ignoring the charge limit you have set. There is no way to prevent forced sleep. Therefore, the only way to solve this problem is to disable charging before sleep. This is what batt
does. It will disable charging just before your MacBook goes to sleep, and re-enable it when it wakes up. This way, your Mac will not overcharge during sleep.
Not that you will encounter this forced sleep only if you, the user, forced the Mac to sleep, either by closing the lid or selecting the Sleep option in the Apple menu. If your Mac decide to sleep by itself, called idle sleep, e.g. when it is idle for a while, in this case, you will not experience this stop-charging-before-sleep situation.
So you suggested not turning of this feature. But What if I MUST let my Mac charge during a forced sleep without turing off disable-charging-pre-sleep
, even if it may charge beyond the charge limit? This is simple, just disable charge limit by setting it to 100% sudo batt limit 100
. This way, when you DO want to enable charge limit again, disable-charging-pre-sleep
will still be there to prevent overcharging. The rationale is: when you want to charge during a forced sleep, you actually want heavy use of your battery and don't want ANY charge limit at all, e.g. when you are on a long outside-event, and you want to charge your Mac when it is sitting in your bag, lid closed. Setting the charge limit to 100% is equivalent to disabling charge limit. Therefore, most batt
features will be turned off and your Mac can charge as if batt
is not installed.
It writes to SMC to control battery charging. This does changes to your hardware, and is a highly privileged operation. Therefore, it requires root privilege.
It is also possible to run it without sudo
. But I decided not to, because I want to make sure only you, the superuser, can control your computer, and to prevent accidental misuse.
If you want to use the cli without sudo, e.g. sudo batt limit 80
, you can install the daemon with --allow-non-root-access
flag, i.e., sudo batt install --allow-non-root-access
. This will allow non-root users to access the daemon. However, this is not recommended from a security perspective.
If you are concerned about security, you can check the source code here to make sure it does not do anything funny.
Since it is a hobby project, I want to balance effort and the final outcome. Go seems a good choice for me. However, C is required to register sleep and wake notifications using Apple's IOKit framework. Also, Go don't have any library to r/w SMC, so I have to write it myself (charlie0129/gosmc). This part is also mainly written in C as it interacts with the hardware and uses OS capabilities. Thankfully, writing a library didn't slow down development too much.
By default, batt
daemon will have its log level set to debug
for easy debugging. The debug
logs are helpful when reporting problems since it contains useful information. So it is recommended to keep it as debug
. You may find a lot of logs in /tmp/batt.log
after you use your Mac for a few days. However, there is no need to worry about this. The logs will be cleaned by macOS on reboot. It will not grow indefinitely.
If you believe you will not encounter any problem in the future and still want to set a higher log level, you can achieve this by:
sudo launchctl unload /Library/LaunchDaemons/cc.chlc.batt.plist
(batt must be stopped to change config so you can't skip this step)/Library/LaunchDaemons/cc.chlc.batt.plist
and change the value of -l=debug
to your preferred level. The default value is debug
.sudo launchctl load /Library/LaunchDaemons/cc.chlc.batt.plist