While I use PCs for most of my day-to-day work, I have a beloved Macintosh PowerBook 12″ that I use for testing and on-the-go computing. Lately I’ve been having trouble with the battery charging, went through the official resetting of the power management chip, to no avail. Finally I bought a new battery.

On the plus side, the new battery lasts for over 4 hours in normal wordpressing / wireless surfing (the old one was pooping out after about 1.5 hours). However, today the new battery failed to charge after I had flattened it inadvertently; the battery life indicator had gotten stuck (gah) and didn’t alert me to my impending doom. So I plugged the PowerBook into the adapter next to the laptop stand, and…nothing! No charging at all! Mysteriously, the green ring light indicated that the laptop was receiving power just fine. Yet, the NEW BATTERY was not charging. WTF!

I swore, I fiddled, and I swapped batteries back and forth. I reset the Mac’s PMU and zapped my PRAM, and was about to try reinstalling all of Mac OS X from scratch when I thought of something: the power supply. I have two: one is plugged in near the laptop stand, and one that’s in my laptop bag for travel. I just tried plugging in the spare, and lo, the battery started charging! WTF WTF!

I didn’t see this “solution” mentioned in the resources I’ve seen online, so if you’re troubleshooting a “battery does not charge” issue, try using a different power adapter and see if that makes a difference.

Really geeky thoughts follow.

Power Supplies :: The Weakest Link?

Speculation: The electronics in the Apple 65W Portable Power Adapter are busted? I didn’t realize that it might be more than just a “dumb” adapter. Or, maybe the adapter is, for some reason, delivering insufficent power to both charge the battery and run the laptop at the same time. In either case, there is no diagnostic that indicates that there is a fault…irking.

Power supplies have a habit of dying on me. Over the past few years, I’ve had the following supplies die:

• Two external Firewire Enclosure power adapters
• Four PC Power Supplies
• My Tivo’s Power Supply (the entire unit was replaced under extended warranty)
• My Bondi-blue iBook power adapter
• And now, apparently one of my PowerBook power adapters

I aggressively condition the power in my house to prevent things like voltage spikes from frying my gear, but nevertheless I’d have to say the main things that break are power supplies followed by hard drives.

The problems I’ve experienced—and this is admittedly somewhat speculative—is that over time the supply loses the ability to deliver enough power. My main server, a dual PII-350 box running Windows Advanced Server, is loaded with drives and backup devices. I started to experience intermittent failures with drives staying powered up or booting. When I experience these kinds of failures, the first thing I try now is replacing the power supply with something meaty. I don’t usually skimp on this component unless nothing else is available; sometimes it’s hard to find something large enough on a moment’s notice.

I’m not sure what the deal is with those external power adapters, and why they seem to die.

• In the case of the Firewire enclosures (especially cheap ones), I suspect the adapters are underpowered and are easily killed by big disk drives and DVD-Writers. I have a first-generation Plextor 8x DVD Writer that just ate these things; it would work for a bit, and then it would start flaking out. It’s in a drawer in the bottom of a file cabinet now, because I haven’t wanted to kill any more supplies with it.

• In the case of hard drives in external enclosures, sometimes their internal power supplies degrade to the point they can’t function reliably; it’s particularly an issue with old drives exhibiting signs of stiction. Sometimes you can just move the drive to another enclosure with a new power supply. In 1994, I had a nice external SCSI drive in an Adaptec enclosure, and it eventually died 3-4 years later. I transplanted the drive into another enclosure to see if it worked, and it lasted for another couple of years before dying. I moved the drive yet again to another SCSI enclosure and got another couple years out of it before I moved it to my current server as an internal drive. I don’t keep any critical data on it anymore, but the point is that the drive outlasted 3 power supplies over a period of 12 years (more if you include the power supplies the server has killed; it’s on its 3rd one). Now that I’ve jinxed it I should remove it from the server and use it for something else.

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p>The moral of the story, I suppose, is that after you check that your computer is plugged in, make sure the power supply is working properly. If you are experiencing bizarre, intermittent failures—random shutdown or reboot, occassional data corruption or boot failure, or “random” behavior that doesn’t seem to be software or virus related—try swapping out the power supply and see if that clears it up.

Any power supply engineers want to clarify how these things fail? I slept through most of my analog electronics courses :-)

P.S. This is cool…a blog devoted to power supply design! Yay!