In this space last week I looked at “power banks,” external batteries used to power cell phones and other devices when wall power is unavailable. This is a necessity in Saipan’s blackout-prone environment. Even if they’re not engaging a cell signal, people often use their phones as cameras, video cameras, address books, and so on. I’ve tried a variety of small power banks for cell-phone charging. I had good results with all of them. In this realm some power banks cost less than $12. Prices of $30 to $50 are more typical.
Well, so far, so good.
For some people, though, a cell phone isn’t enough technology to meet the demands of life. So here we climb to the higher end of the power bank realm, namely, those that power laptop computers. This is more demanding, more expensive, and more complicated than the realm of cell-phone power banks.
Here’s something you probably know but I’ll mention it anyway: Your computer’s power brick takes AC (alternating current) power from the wall socket and converts it to DC (direct current) voltage that enters your computer.
Although the AC voltage is standard within various regions of the globe (Saipan meets the U.S. standard of 110 volts) the DC voltage is not standard. It will vary by the model of computer. From what I’ve seen it’s usually in the range of around 14 volts to 20 volts. This information is stamped on the computer’s power brick. So, too, is the amperage.
As for amperage, if you have a power-thirsty computer that sucks a lot of amperage, your power bank might not be able to feed its appetite, so you’ve got to keep an eye on this factor as well. I don’t sweat the amperage factor because only my most efficient and smallest (12-inch screen) computer is earmarked for power bank use. My larger and thirstier laptops are benched when I have no wall power.
As for power banks themselves, since they’re battery-powered their juice is DC.
With this information in mind, we’re now equipped to confront a major fork in the road. This is the DC- vs. AC-fork.
Some power banks only provide DC output. These power banks are surrogates for your power brick. This has the advantage of simple, DC-to-DC efficiency. It has the disadvantage of requiring the same voltage for both the power bank output and the computer input. If these two elements don’t match (or are at least extremely close), you’re dead in the water. Some power banks offer only one DC voltage for output, while some offer several voltages in order to expand the amount of computers they can work with.
Other power banks, by contrast, convert their battery power into AC power. They are, essentially, wall sockets in a box. You simply plug your computer’s power brick into the power bank instead of into a wall socket. This has the advantage of steering around DC voltage compatibility issues. It has the disadvantage of some conversion inefficiency as things flip from DC to AC and then back to DC again.
Here’s another consideration: airline travel. To be allowed onto an airliner I believe that, in general, the limit on a power bank is 100 watt-hours of capacity. There are some details here, but, having been alerted to the issue, you can dig those up when you need to.
How many hours of computer power can we get from these things? That’s really the issue. And it’s an issue I’m still working on. Lately I’ve been trying out the largest-capacity power bank I’ve managed to get my hands on. This is the “Maxoak K2,” which is rated at 185 watt-hours. It typically costs about $135. However, a sale popped up and I landed one for $99.
The Maxoak K2 should, in theory, power my computer for about 25 hours. Although it seems to be in the rough ballpark on that count, I want to get more experience with it before I reach any conclusions. In the meantime, I’ll note that the Maxoak K2 powers laptops via a single 20-volt DC, 5-amp port. Mine has not hiccuped, malfunctioned, or done anything weird during use. It also has four USB ports and a 12-volt DC port. Anyway, that’s where my power bank attention has been focused of late.
Although there are many details to juggle, the news on the power bank front is really all good news. After all, we’ve got more and more ways to keep connected and to keep working when the lights go out.
If you have any comments or insights, I am, as always, happy to hear from you.
In the meantime, my family and I wish everyone in the CNMI a very Merry Christmas!