macbook-battery-manager-wemo

When running on a macOs device with a battery (Macbook) that is plugged into a Belkin Wemo switch this utility will maintain the Macbook at a certain battery charge percent +/- a tolerance by powering the switch on/off as needed.

Disclaimer

I AM NOT A BATTERY EXPERT. HOWEVER, EXCESSIVELY SWITCHING THE POWER ON AND OFF TO YOUR MACBOOK CHARGER WILL SHORTEN YOUR MACBOOK'S BATTERY LIFE. IT MIGHT EVEN DAMAGE IT THE BATTERY REQUIRING A POTENTIALLY COSTLY REPAIR. USE THIS UTILITY AND SETUP AT YOUR OWN RISK AFTER YOU'VE FULLY UNDERSTOOD ITS PURPOSE! I DO NOT RECOMMEND USING THIS FOR VERY LONG. USE IT ONLY FOR TESTING AND EXPERIMENTING.

Summary

Some laptops from Lenovo and others detect when the device is always plugged into power and give the owner the option of holding the battery at a state of partial charge. Lenovo calls it "Conservation Mode" and the purpose is to extend battery life for notebooks that are always plugged into power.

Apple's own website states that if a device is to be stored long term, the battery should be charged to 50% ("Store it half-charged when you store it long term"), even going as far as recommending that the device battery be topped off to 50% at least every six months. See Maximizing Battery Life and Lifespan.

Search the web for keywords like "extending battery performance" will yield countless results with extensive opinions.

Despite the above, Macbooks and macOS provide no mechanism to hold a notebook's charge at a certain percent when it is always connected to power.

I've read of some people hacking the charge cable to achieve some charge blocking, but messing with a cable seemed like a bad idea to me, though I admit possibly managing battery by switching power on/off very frequently might be equally as bad (likely worse)!

Enter this command line utility: when running on a Macbook that is also plugged into a Wemo switch, this utility will monitor the notebook's charge and then either flip the Wemo switch on or off to maintain the desired charge +/- a tolerance.

By the way, I don't recommend using this for more than just playing/testing. Why? Charing/discharging like this will eat up charge cycles on your Macbook's battery at an increased rate. For instance, in 4 to 6 hours of testing, I saw two charge cycles added to my Macbook's battery charge cycle count. As I am not a battery expert, I'm not sure what the long term impact is on the battery of coming close to, or even exceeding this charge cycle count! Also, charging like this for short periods of time, repeatedly, likely causes temperature fluctuations in the battery that are not usual. In short, this is a project for learning and experimentation and I do not recommend using it for anything other than learning for a short period of time!

Installation

To install this utility globally:

$ npm install -g macbook-battery-manager-wemo

Usage

After installing globally, run this utility with command line arguments to suit your needs.

For example, to control a switch called macbookswitch so that it maintans a 70% charge +/- 10% with a check interval of every 5 minutes:

$ macbook-battery-manager-wemo \
  -s "macbookswitch" \
  -p 70 \
  -t 10 \
  -i 5

Or using the long arguments:

$ macbook-battery-manager-wemo \
  --switchname "macbookswitch" \
  --percent 70 \
  --tolerance 10 \
  --interval 5

You can also execute the command in a single line! We broke it up into multiple lines using the '\' line continuation character for redability.

The command line arguments are as follows:

• (required) -s, --switchname "switch name"
  • The name of the Wemo switch to control. Must match the name in your Wemo app.
• (required) -p, --percent [integer]
  • The battery target percent to aim for (this will be maintained within the tolerance). Must be between 30 & 90 inclusive.
• (required) -t, --tolerance [integer]
  • Battery percent tolerance (battery will be maintained at target percent +/- tolerance). Must be between 1 & 30 inclusive. Percent - tolerance must be >= 20. Percent + tolerance must be <= 90.
• (required) -i, --interval [integer]
  • The interval at which to check for battery charge (in minutes). Must be >= 1
• (optional) -v, --verbose
  • Produce verbose logging (outputs logs on every interval check).

Once the command starts, you'll see output similar to:

Battery manager starting up...
Looking for your-device-name...
Wemo Switch found: your-device-name. Will maintain 70% +/- 7%.
Switch your-device-name is off

Or if you enable verbose:

Battery manager starting up...
Looking for your-device-name...
Wemo Switch found: your-device-name. Will maintain 70% +/- 7%.
Target: 70% +/- 7%, Current: 92%, Ensuring switch is off.
Switch your-device-name is off
Target: 70% +/- 7%, Current: 89%, Ensuring switch is off.
Target: 70% +/- 7%, Current: 87%, Ensuring switch is off.

To stop the utility, simply press CTRL+C. Ensure that the Wemo switch is at the desired setting once you stop the utility. All Wemo switches have an on/off button you can manually press.

FAQ

• What configuration is the best?
  • I have no idea. See the Disclaimer and Summary above. This is something you'll need to research and decide for yourself.
• What setting do I use?
  • I wrote this utility for fun and to experiment with Wemo switches doing something useful, so I'm not actually using it regularly because it's a bad idea and will likely damage the battery! However, if I was going to use it, I would likely keep charge at 70% +/- 10% based on what I've been reading on various posts.
• What the heck is a Wemo switch?
  • Wemo switches are power outlets made by Belkin that can be controlled via a Belkin supplied app as well as other services like IFTTT, Alexa and others. You can basically turn these switches on/off via software! Generally used for lamps, these devices have become popular with the internet of things revolution.
  • You can order Wemo switches from Amazon and other places. Here are Amazon links:
    • Wemo Mini Smart Plug
    • Wemo Insight WiFi Enabled Smart Plug
    • Wemo Switch Smart Plug
• Are Wemo devices secure?
  • That's a big question that I'm not going to try to answer fully here.
  • However, before writing this utility I always thought that Wemo devices sure had some kind of authentication. Yet, this utility is able to find these devices on the network and then send instructions to them (turn on / turn off) with zero authentication. So, it seems that any device on the network that understands the Wemo protocol can control these. As such, I would only install these in a network that is already controlled by other mechanisms. I also would not connect anything of much significance to these switches. For instance, if someone connects to my network and messes with my lights, that might not be something of much concern. If you have a WiFi network only, the WiFi security is good enough on most days. However if your network is also wired you should consider that anyone can theoretically plug in a notebook to your wired network and control these devices. Sure, ther are ways to protect a wired network to not allow unrecognized devices, but most home users (and even small businesses) likely won't have taken the time to do this.
  • Caveat: It's possible that I never bothered to enable device authentication on my Wemo switches, though I honestly don't remember seeing such a thing in any of the Wemo setup wizards or prompts! If you know something about the security of these devices, by all means let me know. Open an issue and let me know your thoughts.

Requirements

This package supports macOS 10.11 or newer. Please report if this works on older versions of macOS via issues so that we can update the requirements check.

Limitations

At present, the API returns status of the primary device's battery. Are there Macs with multiple batteries? Open an issue and let us know!

Under the Hood

This package uses the macos-battery package which in turn uses macOs's pmset -g batt command to get status from the OS.

License

MIT © Eric A. Soto