The Mobile Mac

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

- 2006.06.05 -Tip Jar


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

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

On an Airplane

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

My 12" PowerBook runs for about four hours on a charge when I'mwriting - that drops to about 2-1/2 hours for DVD movie playback. SinceI can't sleep on airplanes, I carry three batteries, which gets methrough three movies with an hour or two left to get a little workdone, if needed. The extra weight of three batteries are one reason whyI 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 youhappen to have a 15" or 17" aluminum PowerBook (I'm not sure about theMacBook Pro), this isn't necessary. The larger aluminum PowerBooks havea capacitor that maintains power to memory for a minute or so, allowingyou to swap batteries without shutting down - just close the lid to putyour PowerBook to sleep, swap the battery, and open the lid.

Safe Sleep

The final generation of large PowerBooks (the high resolutionmodels) added an additional feature called Safe Sleep, which writes thecontents of RAM to a file on the hard drive as the computer goes tosleep. This is seamless to the user and only comes into play if thepower in the capacitor runs out, in which case you have to press thepower button to turn the PowerBook on and wait about 20 seconds whileit reads the data from the hard drive back into memory. This isessentially the same as Windows Hibernation (suspend to disk), onlymuch 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 modellacks the capacitor. Fortunately, I found a great Unix hack written by Andrew Escobar that enables the SafeSleep function on the 12" PowerBook and various iBooks. The websitementions success on some desktop Macs as well, but when I tried it onmy 1.5 GHz G4 Mac mini, notonly did it not give me the safe sleep function, it also made itso that the computer would not wake up from sleep. Your mileage mayvary.

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 onlyrequirement is that you should watch the front of your computer andwait until you see the pulsing sleep light, which only begins after thecontents of RAM have been written to the hard drive. If you pull thebattery before the write is completed, your computer will notresume.

Another thing to consider is that the more RAM you have installed inyour 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 8seconds from lid closure until the sleep light comes on. Unless I amchanging batteries, this is a non-issue, as I just close the lid andput the computer in my bag (gently, as I really don't want to testApple'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 getlucky and can sit near AC power, which is clearly the best option whenavailable. Sometimes, however, there just is no such luck. Next month,I'll be attending a four-day legal seminar in Texas and plan onbringing my trusty PowerBook with me. I can barely read my ownhandwriting, so sufficient power is a must.

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

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

For this reason I ordered anexternal charger so that every morning I'll have three freshbatteries, ready to go. US$150 is a bit steep, but it's a lot cheaperthan the price of the seminar, which would be wasted if I was fallingasleep in each session because I kept waking up during the night tocharge batteries.

This charger also has a deep conditioning cycle that is moreconvenient 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 whatsort of AC connector they use where you're going and get an appropriateadapter. There are plenty of travel kits that contain multiple adaptersout there, but these are often very overpriced. Korea uses a wide twoprong plug, and I got an adapter for it in Seoul years ago for under adollar.

All PowerBook and iBook AC adapters will automatically sensedifferent voltage, so no worries about converters - only the shape ofthe plug. Back in 1993 I even used my ancient PowerBook 145B on 220 volts in Koreawithout incident.

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

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

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

* Editor's note: I really like the NewerTech65W power adapter (US$50 from OWC) and the MicroAccessories 60W Power Adapter ($35). These are fairly compact,reasonably priced, and uses the same AC cord you're likely to find onportable radios and small household appliances - easy to replace ifthey're lost or damaged. dk

Battery Maintenance

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

First of all, do yourself a favor and buy a second battery at thesame time you buy your laptop. Just sitting in the computer with the ACplugged in is bad for your battery, as is using the same one constantlywithout giving it a rest.

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

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

With this three month rotation scheme, my three batteries, despitebeing a year old, still deliver their full capacity, and chances arethey will continue to provide sufficient charge for my needs until itis time to upgrade to a newer computer.

While I have worked out a system of battery and AC power over theyears, it's obviously not perfect. I seriously considered using an IBMThinkPad X32 for this trip because of its abilities to run for 10 hourswithout swapping batteries (main cell and clip-on auxiliary cell) andcharge at night as a single unit. I have access to such a machine, butthe convenience of its power system does not mitigate having to useWindows.

Perhaps someday Apple will give us a machine that runs that longbetween charges, but until then, my safe-sleeping PowerBook and itsthree batteries will get the job done. LEM

Andrew J Fishkin, Esq, is a laptop using attorney in Los Angeles, CA.

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