Power On The Go

When it comes to operating life on the go, it seems like more is never quite enough. Who among has never wished for just one more half hour of life from our computer or cell phone? Fortunately, there are some pretty good options out there for extending our time away from the nearest AC outlet. Let’s quickly discuss some of them.

Of course, one of the most obvious options is to carry a second battery for your device of choice. However, I’m going to skip over this option because many devices (most infamously the iPod and iPad, but also the HP Slate 500 and the Asus EP121) don’t feature user “swap-able” batteries. However, there are several brands of external battery that feature capacities that are two, three, even as much as eight times the capacity of your typical “small” laptop PC. Possibly the best and largest survey of external batteries that I have seen recently is here:

www.tomshardware.com/reviews/notebook-battery-external-power-supply,2821.html
(credit to WildParadise at TabletPCReview for bringing this link to my attention)

Having had a fair bit of experience with external batteries, I’m a believer in the “use it or lose it” approach. If you buy an external battery and then simply put it in a drawer, using it only occasionally, your chances of eventually finding that battery prematurely dead or significantly degraded are quite high! On the other hand, if you use it on a regular basis your battery will likely last for years. My last external battery, an APC UPB-80 just died after almost three years of service. If I wasn’t using it while I was out and about, I used it to recharge my TC1100 each night, then recharged the UPB-80 as needed.

Perhaps this idea of regular use strikes you as “high maintenance.” Is there another alternative? Why yes, there is, particularly if you spend a lot of time in a car; a DC-to-AC inverter. Inverters are small-ish devices that plug into your car’s DC power socket (what some of us used to know as the cigarette lighter socket) and output 110V AC. Using this approach, you would simply plug in your device’s AC adapter just as you would if you had an AC wall socket in your car.

Most inverters are one or the other of two types, either “modified sine wave” output or “true sine wave” output (there are also “square wave” inverters; I would avoid these). The former is less expensive and outputs a “two-step” square-wave approximation of wall plug AC power. Although crude, the modified sine wave waveform is usually close enough to a smooth sine wave shape to allow electronic gadgetry of all types to work with only a little increased heat or RF noise (which might, for example, cause interference with your car’s AM radio). Needless to say, the true sine wave output looks almost exactly like wall plug AC power (typically less than 3% total harmonic distortion), so your electronics work completely normally. Ironically, even true sine wave inverters can have noisy (both RF and audible buzz) circuitry, so be sure that anything that you buy can be returned! Duracell, Belkin, Cobra and Xantrex are just a few of the makers of modified sine wave inverters. Samlex, Xantrex and GoPower are a few who make true sine wave inverters. If you shop on sites like Amazon, don’t forget to check the reviews for helpful insights into individual devices and their pros and cons.

And one final note. Most cars feature power sockets that are limited to 12V at either 10A or 15A. This translates to 120W or 180W of maximum draw respectively. Most laptop AC adapters are 90W or less, so are perfectly OK for car use. If you use a technical (workstation) PC, you may have a 120W AC adapter; pushing it, but maybe still OK. Just remember that your car is like your home; don’t draw more watts than your socket can supply; check your owner’s manual!