It seems to be a never-ending battle – trying to get the most out of your laptop battery. It always seems like you run out of battery power at the worst possible moment. And as amazingly convenient as the OWC Data Doubler makes adding a second drive to your MacBook Pro, that just means you now have two drives sucking down power, rather than just one.

Of course, the easiest thing to do would be to replace any platter-based hard drives with an OWC Solid State Drive. Fewer moving parts means less power draw. They also mean less heat, which means the fans run a little less, which also reduces energy consumption.

However, for storing all your data, platter-based drives still have the best cost-per-gigabyte ratio. That’s why many people have chosen to install one of each in their MacBook Pros with a Data Doubler; which solves the storage/performance problem, but doesn’t do much for your battery.

The next logical place to look is in your Energy Saver preference pane. Depending on your MacBook Pro model, there are options to tick for “better battery life” or “higher performance,” as well as a number of sliders to adjust display and computer sleep. There’s also a box to “Put the hard disk(s) to sleep when possible.” Checking this one spins down the drive after about 10 minutes of inactivity.

However, that’s a while before any energy savings kick in. Fortunately, OWC customer Andrew Bodenstein wrote in to remind us that there’s a way to adjust this in the Terminal, using the pmset utility. This utility controls power management options, similarly to the Energy Saver control panel, but with a greater level of detail. We’re going to focus on just changing the disk sleep time.

A quick entering of man pmset into the Terminal will give us a full listing of all the commands and arguments we can use to change things using pmset. We’ll save you the trouble, though, and give you just what you need to adjust the spindown time. The command you’ll want to enter is:

sudo pmset -a disksleep 5

Because you should never just blindly enter in a Terminal command without knowing what it does, I’m going to break this command down piece-by-piece.

• sudo - allows a standard “admin” user to run programs usually reserved for the “root” user. These are usually processes that affect the system as a whole – like this one.
• pmset - this is the name of the utility we’re using.
• -a - this “flag” tells the pmset utility that we’re applying it to all power configurations: battery, charger, and uninterrupted power supply. If you want to affect JUST when you’re on battery power, change this flag to “-b”
• disksleep - this is the parameter we want to change: disk sleep time. This parameter is for 10.5 and later; in previous OS versions, you should use “spindown” instead.
• 5 - this is the number of minutes the system waits before sleeping the disk. OS X’s defaults are 10 minutes. We halved it here, so it spins down faster, but not so fast that it’s always spinning up (which would be counter to our needs). You may need to adjust this number to a point that works best for you.

After you enter the command, hit Return and you will be prompted for your username and password. Enter those in, and your settings will be changed.

Now, after five minutes (or whatever number you put in) your drive will spin down and go into a “sleep” state where it draws less energy – giving you longer battery life.

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