Watts: Keep Your Mac’s Battery in Tip-Top Shape

You don’t need this app. There are good guides available on the Apple website to help you get the best performance and extend the life of your Mac laptop’s battery. You can even download from that page an iCal file that will add periodic reminders to your calendar, so that you’re more likely to remember to calibrate your battery. Follow that advice, and respond to the reminders, and you and your computer’s battery will be fine.

I’m on the second battery in my MacBook (which is coming up to its fourth birthday this week). Apparently it’s in quite good health at the moment, though it’s lost 18% of its capacity. You see, I’m not so good at remembering to calibrate it, and because I tend to use it all over the house, it’s constantly being plugged and unplugged, and is drained completely on most days. I’m not so hot on looking after batteries…

And so, though I know I don’t need it, I think Watts is well worth having. Read on for an introduction to this little app that could make it easier for you to look after your laptop’s battery.

What it Looks Like

Watts runs as a menu bar application – you can use it in place of the standard OS X battery monitor.

In the Menu Bar

In the Menu Bar

Click on the icon, and you’ll see a dropdown menu with a little more summary information:

Menu Bar Dropdown

Menu Bar Dropdown

The top section summarises your battery health and charge remaining, and the current battery state – whether or not your computer’s plugged in. The Show submenu lets you choose the form of the menubar information: you can opt to display the battery icon on its own, or add the time or percentage of battery charge remaining; or you can switch off the icon and show either the time or percentage on its own.

The Energy Saver Preferences link is useful for getting to the Preference Pane that controls your Mac’s energy use settings – you can also go there to turn off the built-in battery status monitor and opt to use Watts instead.

How it Works

The Calibration menu is where Watts gets down to its real work.

The Calibration Menu

The Calibration Menu

You’ll see that Watts remembers when I last calibrated the battery, and lets me know when I should do so again – six weeks after the last time. Click on the ‘Show Calibrations History Log’, and a new disclosure panel lists the dates on which the battery was properly calibrated:

The Calibration History

The Calibration History

The panel beneath that information changes as you go through the stages of calibration – in this screenshot, it’s showing what needs to be done in the first stage, though the information is greyed out since my machine’s not plugged in, so Watts knows that I’m not at that phase in the process.

As you follow the steps, notifications will pop up to remind you to move to the next stage in the process. I found this really useful, because I can never remember whether it’s three or four hours you’re supposed to let the machine rest after completely discharging the battery… Actually, it’s five hours, and you need to make sure it’s unplugged, which is the guidance given in step 5 of the calibration process.

Other Settings and Information

The other tabs on the interface let you see more detailed information about your battery: current number of charge/discharge cycles, battery capacity and current condition, and a textual summary of the same information:

Battery Information

Battery Information

The Notifications tab lets you set various kinds of reminders. Watts can work with Growl to let you know whenever the power cord is plugged in or removed.

This is worth knowing when you’re in the process of calibrating, since you need your machine to rest in either a charging or discharging state for various lengths of time, and Tiddles the cat can quite easily unplug a MagSafe power cord if he so chooses.

I also appreciate the reminder after 30 hours of plugged use that it might be a good idea to unplug for awhile and let the battery discharge a bit. And although I’ve not made use of the Long Term Storage reminders, I can see they would be helpful if you knew you were going to be away from you Mac for more than six months (*shudder*).

The final tab simply lets you manage how Watts works with the rest of your system – whether it starts automatically when you login, whether it uses a grayscale rather than a colour icon, and at what point after your last calibration it lets you know that it’s about time to run through another.



The Calibration and Information tabs have some useful information available from their help menus – click on the word ‘help’ at bottom right, and you’ll see (grammatically imperfect, but) clear explanations of various aspects of the app as well as top-tips for battery care:

Calibration Information

Calibration Information

These are nicely done – the information is clear and helpful, and some care has been taken in presenting it well.

In Conclusion

You don’t need this app. You will probably be fine without it, especially if you’re someone who remembers to do the right thing with your Mac’s battery. If you’re like that, I’m not like you, and I find Watts really helpful – and my guess is that many readers will be like me in this regard.

Watts is cheap and elegantly designed; it does a good job, and could save you needing to purchase a new MacBook battery a year down the line!


Your battery needs to be recalibrated from time to time to keep the onscreen battery time and percent display accurate, and to keep the battery operating at maximum efficiency. Watts helps you do just that!



Add Yours
  • Nice app with outstanding interface design. However, as you said, i do not need it.

    • I have to disagree about the interface design… (warning, long-winded critique ahead)

      Some text elements are incredibly low contrast and/or tiny, making them unreadable or barely readable. There’s also lots of this light grey text on dark grey background with a highlight effect for no reason. Why not just make the text white on dark grey (or black on light grey like everything else), and thereby more readable? Why drop the contrast for no reason? Legibility is basic. If you can get legibility down, the interface becomes worthless.

      …and to nit-pick, there are also all those unnecessary lines across the windows dividing it into sections, and each section has a barely visible title. What’s the point? If you need a title, you need it to be visible. If you can get away with it being nearly invisible, you don’t need it. Also, imagine those lines across the interface not being there. Would you really get lost and not know what’s going on? It’s already divided up enough by the toolbar buttons. The sections are just visual noise and an unnecessarily deep hierarchy.

      I like when people bother to make something stylish and functional, but I think this UI is just stylish. I want to dissuade people from calling something that’s merely pretty “outstanding interface design.”

      • If you can’t*** get legibility down…

  • Amazing app i was actually looking for something like this for my mac. Great post and worth buying.

  • I had no idea you had to calibrate your battery. I am on my second battery and my MacBook just turned two. Might well be worth the $7.

  • Hello. I have one question. I know, that apple recommends calibrating your battery, but I few months ago I read an article about lithium-ion polymer batteries (wich are also used in macbooks), that nothing is worse, than giving your battery a “shock therapy” – fully discharge it. In the post was also recommended charging your battery, when it reach 35%-50% of charge. Wich one recommendation is true, or better?

    • When you like to charge, just plug in any time to let it charge regardless your current battery level.

      However, you need to do a full discharge/charge about every month.

    • I think Apple’s website has specific information about batteries, which this app seems to put to work (whereas Apple doesn’t even bother to tell you about it until you go searching for it on the support site).

      Basically, Apple sez: Don’t let your battery drain completely.* Optimal use would be someone using the battery at work/school during the day and then charging it each night. *Occasionally calibrate the battery for longer life (the steps of which are described by this app’s calibration helper).

      …but you’ll have to check it out on your own to be sure I’m getting that all right. Just search Apple’s site.

      • Hi. Actually when i got my first macbook the first thing i done was to research for this kind of information on “maintaining” my battery healthy.

        Its pretty clear and easy how to use it to remain “Good” in System Profiler > Power.

        Just use it normal. Unplugged when you dont have where to plug it. When ur at home just plug it, but if u use it “always” at home, then u have to do a point of balance (like 2 days ON, 2 OFF). Simple.

        I have mine original macbook/battery for 3 years, Health Information: Cycle count: 381; Condition: Good

        INFO Battery Health Monitor app: Current Capacity: 98%
        INFO CoconutBattery app: 96% (its always pessimist rotfl…)

        One thing that i dont see usual refereed in websites, is that we can just use the “Help” Menu in Finder and type

        battery calibrating and will appear the “Calibrating a MacBook or MacBook Pro battery” (in my case). And it says everything.


  • You know what ?
    This is a great app. In fact to me, it typifies both the type and design of a classy Mac application.
    Thanks for the review. I would have never found this, otherwise.

  • Thanks for the information, it is worth try

  • You should never intentionally fully cycle the battery.


    Apple bases its replacement policy on how many cycles your battery has undergone.

    If it is over 300 cycles, Apple will NOT replace the battery, even if it is under a year old and performing poorly.

    • Bill you’re talking rubbish. Are you aware of what a battery cycle is? Have a look at: http://support.apple.com/kb/ht1519 and read Note 2 at the bottom. I shall copy and paste anyway:

      A charge cycle means using all of the battery’s power, but that doesn’t necessarily mean a single charge. For instance, you could use your notebook for an hour or more one day, using half its power, and then recharge it fully. If you did the same thing the next day, it would count as one charge cycle, not two, so you may take several days to complete a cycle.

      So whether you fully cycle the battery or use it down to 50% twice, it’s all the same, it counts as a cycle.

  • I didn’t realise I needed it until my daughter rang to con money out of me for a new battery! She chews through them like a beaver through bark…. grrrr. So I sure as heck think I need it now.

    Rising kids is nothing like they showed us Brady Bunch!

  • This is a great app! If you’re concerned about battery issues, you should also check out low battery saver. It makes sure your Mac sleeps before the battery completely runs out and lets you set a warning to alert you that the computer is about to sleep. (http://itunes.apple.com/us/app/low-battery-saver) It won’t fix your battery problems but at least you won’t lose your work, have to restart your computer etc.

  • Sorry, the correct link to low battery saver is this:http://itunes.apple.com/us/app/low-battery-saver/id480383312?mt=12

  • In twenty years with Macintosh I’ve never been more frustrated by an app. Someone who installs the trial and then gets busy or travels or for any other reason lets the trial expire is SOL. There is no reference anywhere to how to enter a registration at this point, or even how to launch the darn thing! Nice design but poor execution and documentation. Certainly not worth the trouble when there are simple and free ways to recalibrate.