Power Strategies for Using Your 'Book in the Field: Batteries and AC Adapters

Power

Power means many things, but in the context of the Mobile Mac, it's simply the ability to turn on and use your computer wherever and whenever you need it.

As someone who's traveled with a laptop for over 13 years, power is something that I've struggled with constantly and still don't have handle on. Put simply, you need to have access to AC power or enough batteries to get you through your project.

On an Airplane

Twice yearly I fly from Los Angeles, CA, to Seoul, Korea, a flight that takes about 12 hours. During that time, I don't have access to AC power, and very few airplanes have DC power back in coach. That means packing a lot of batteries.

My 12" PowerBook runs for about four hours on a charge when I'm writing - that drops to about 2-1/2 hours for DVD movie playback. Since I can't sleep on airplanes, I carry three batteries, which gets me through three movies with an hour or two left to get a little work done, if needed. The extra weight of three batteries are one reason why I like small and light notebooks, as that weight adds up fast.

Changing batteries used to mean shutting down the computer, switching the battery pack, and then booting up again, but if you happen to have a 15" or 17" aluminum PowerBook (I'm not sure about the MacBook Pro), this isn't necessary. The larger aluminum PowerBooks have a capacitor that maintains power to memory for a minute or so, allowing you to swap batteries without shutting down - just close the lid to put your PowerBook to sleep, swap the battery, and open the lid.

Safe Sleep

The final generation of large PowerBooks (the high resolution models) added an additional feature called Safe Sleep, which writes the contents of RAM to a file on the hard drive as the computer goes to sleep. This is seamless to the user and only comes into play if the power in the capacitor runs out, in which case you have to press the power button to turn the PowerBook on and wait about 20 seconds while it reads the data from the hard drive back into memory. This is essentially the same as Windows Hibernation (suspend to disk), only much faster and occurring in the background, only when sleep (suspend to RAM) loses power.

My problem is that I travel with the 12" PowerBook, and that model lacks the capacitor. Fortunately, I found a great Unix hack written by Andrew Escobar that enables the Safe Sleep function on the 12" PowerBook and various iBooks. The website mentions success on some desktop Macs as well, but when I tried it on my 1.5 GHz G4 Mac mini, not only did it not give me the safe sleep function, it also made it so that the computer would not wake up from sleep. Your mileage may vary.

On my 12" PowerBook, this hack is just what this model was missing. I can now close the lid, wait a few seconds, and then swap batteries, just like on a large, capacitor-equipped PowerBook. The only requirement is that you should watch the front of your computer and wait until you see the pulsing sleep light, which only begins after the contents of RAM have been written to the hard drive. If you pull the battery before the write is completed, your computer will not resume.

Another thing to consider is that the more RAM you have installed in your computer, the longer this function will take in both directions. My 12" PowerBook is topped-off with 1.25 GB of RAM and takes about 8 seconds from lid closure until the sleep light comes on. Unless I am changing batteries, this is a non-issue, as I just close the lid and put the computer in my bag (gently, as I really don't want to test Apple's hard drive sudden motion detector).

Batteries in the Classroom or Conference Room

This is the other area where I run into trouble. Sometimes you get lucky and can sit near AC power, which is clearly the best option when available. Sometimes, however, there just is no such luck. Next month, I'll be attending a four-day legal seminar in Texas and plan on bringing my trusty PowerBook with me. I can barely read my own handwriting, so sufficient power is a must.

With the screen dim, I can coax somewhere between 12 and 15 hours out of my three batteries on the 12" PowerBook, which I'd imagine will be sufficient for each day. The problem is recharging. Each day of the seminar is very long, starting at 8 a.m. and finishing up at around 9 p.m., with the evening sessions optional trial workshops.

Since the computer will not be in constant use, I don't anticipate any problems running out of power in a typical day, but recharging will be a real issue at night. The PowerBook takes about three hours to fully charge one battery, and while I could get all three charged , it would involve waking up twice in the middle of the night to do it.

For this reason I ordered an external charger so that every morning I'll have three fresh batteries, ready to go. US$150 is a bit steep, but it's a lot cheaper than the price of the seminar, which would be wasted if I was falling asleep in each session because I kept waking up during the night to charge batteries.

This charger also has a deep conditioning cycle that is more convenient and thorough than running the battery down in the PowerBook, which I'll get to in a bit.

AC Power

AC power is often overlooked when traveling.

First, if you're going overseas, it's a good idea to find out what sort of AC connector they use where you're going and get an appropriate adapter. There are plenty of travel kits that contain multiple adapters out there, but these are often very overpriced. Korea uses a wide two prong plug, and I got an adapter for it in Seoul years ago for under a dollar.

All PowerBook and iBook AC adapters will automatically sense different voltage, so no worries about converters - only the shape of the plug. Back in 1993 I even used my ancient PowerBook 145B on 220 volts in Korea without incident.

The next thing you need is a second AC adapter. AC adapters have a rather high failure rate compared to other laptop components, and if your adapter dies, chances are a second one won't be immediately available. I always throw a spare into my suitcase, just in case. I've only needed it once, when the adapter for my then-new PowerBook 5300c stopped working, turning my 7 lb. PowerBook into a useless shoulder weight.

A second AC adapter, or even a third, is very convenient even when you aren't traveling. I keep one plugged in by my bed, another at my family room desk, another in my office, and a fourth in my computer bag. They aren't cheap,* but I never find myself out and about without an adapter, and my adapters will all last longer without the wear and tear of constantly being set up and packed away.

It's also just very convenient to have an adapter ready in the places where I usually work.

* Editor's note: I really like the NewerTech 65W power adapter (US$50 from OWC) and the Micro Accessories 60W Power Adapter ($35). These are fairly compact, reasonably priced, and uses the same AC cord you're likely to find on portable radios and small household appliances - easy to replace if they're lost or damaged. dk

Battery Maintenance

Finally I'd like to talk a bit about maintaining your batteries, as these things are not cheap (generally well over US$100).

First of all, do yourself a favor and buy a second battery at the same time you buy your laptop. Just sitting in the computer with the AC plugged in is bad for your battery, as is using the same one constantly without giving it a rest.

I have three batteries for my 12" PowerBook. I put a big 1, 2, and 3 on them, and then in smaller letters I label the months. Battery number one is used January, April, July and October, and so on for batteries two and three. Batteries are always removed fully charged, and when that battery comes back into rotation (or before I travel), I run down whatever remaining charge there is and charge it back up fully.

The external charger makes this even easier, as I just condition the battery before returning it to use.

With this three month rotation scheme, my three batteries, despite being a year old, still deliver their full capacity, and chances are they will continue to provide sufficient charge for my needs until it is time to upgrade to a newer computer.

While I have worked out a system of battery and AC power over the years, it's obviously not perfect. I seriously considered using an IBM ThinkPad X32 for this trip because of its abilities to run for 10 hours without swapping batteries (main cell and clip-on auxiliary cell) and charge at night as a single unit. I have access to such a machine, but the convenience of its power system does not mitigate having to use Windows.

Perhaps someday Apple will give us a machine that runs that long between charges, but until then, my safe-sleeping PowerBook and its three batteries will get the job done.