External Battery Roundup: Stay Away From The Wall Socket

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Battery life is always such a big deal in our mobile coverage (often because gaming systems fall so short). But don't feel limited by the built-in power source. Today we round up 15 external batteries that can keep you running longer away from a socket.

Background: The Technical Stuff

Inside Your Laptop: Power Distribution

Remember your desktop system? The power supply has 5 V, 3.3 V, and 12 V power rails. Those exist on your mobile system as well. But on a notebook, the power brick doesn't deliver those three voltages to the motherboard, as a PSU does. Instead, the brick delivers a steady voltage to your notebook's input connector. After that, voltage regulators on the laptop motherboard do the rest of the work to output voltages that the CPU, graphics processor, storage and add-in cards can use.

Displays are a different beast altogether. Older CCFL LCD panels need a voltage higher than what your notebook’s power supply can deliver. In order to achieve that higher voltage, a component called a power inverter is used to convert back to a low-frequency AC current. The existing generation of notebooks use LED-based LCD panels, which don't have this high voltage requirement, as they are solid-state devices. Instead, LED backlights operate off of +5 or +12 VDC. LEDs use less power than CCFL backlights; additionally, the lack of a power inverter translates into better efficiency as well.

How does the battery all tie in? The battery supplies power to the input side of the regulators, just like power coming from the wall socket would if you connected that way. However, there is a separate charging circuit. This diverts power from the AC adapter before it gets to the voltage regulators so that your battery charges. This charging circuit is the reason why the voltage on the AC adapter is always rated higher than the one stamped on the battery. You need a higher voltage to charge your battery.

Andrew Ku
27 Comments Comment from the forums
  • lashabane
    Excellent article. I had an idea that this stuff was out there but never really bothered to look. If the 4-5 hours I get from my Asus 1215t begins to not cut it, I now know where to look. Thanks!
    Reply
  • zodiacfml
    I did not understood any of the technical reading especially the part about the desktop PSU.
    At one point, it is stated that AC adapters have higher voltage than the battery on a notebook so that it can be charged. Then, how can a external battery damage a notebook's electronics with a higher voltage (only if it's too high)?

    It is not stated how to set the external battery voltage correctly. What then is the correct voltage? Correct me but I believe the voltage has to be equal that of notebook battery.
    Reply
  • burnley14
    It's pretty remarkable that after page 2 I could guess who the author of this article was (without looking of course) due to the thoroughness and good grammar/lack of typos. Hats off to you yet again, Mr. Ku. Job well done as always.
    Reply
  • @zodiacfml

    it's simple really, AC adapter spit out AC, Batteries spit out DC
    Reply
  • nukemaster
    zodiacfmlI did not understood any of the technical reading especially the part about the desktop PSU.At one point, it is stated that AC adapters have higher voltage than the battery on a notebook so that it can be charged. Then, how can a external battery damage a notebook's electronics with a higher voltage (only if it's too high)? It is not stated how to set the external battery voltage correctly. What then is the correct voltage? Correct me but I believe the voltage has to be equal that of notebook battery.Your guess is actually right. The battery with its voltage set too high can damage the notebook.
    If you need to know the voltage required, you just check on your laptop AC adapter or power brick. It is not always the same as the battery.

    For instance, a Compaq R3000 has an 18.5 volt AC->DC(120w) power supply and its battery is only 14.5 volts. The voltage regulators in the laptop(in the charging system) it self cut it down to the needed 14.5-15volts to charge the battery.

    Also note that the AC adapter does NOT spit out AC it in fact spits out DC(it has a rectifier to convert AC to DC).

    As you can see by this picture(you have to click the link), The adapter takes in AC 120V and spits out DC 18.5V. AC is shown with a ~ and DC with a --_---_-- cant make it on here, but you get the point.
    http://img269.imageshack.us/img269/1950/powerw.jpg
    Reply
  • Onus
    Thanks for the comments on Digipower. I've placed them on my personal "Do Not Buy" list.
    Reply
  • Luscious
    Quite a different experience on my end testing the Energizer XP8000 and XP18000.

    For my smartphone and MiFi, the XP8000 just can't be beat. 5x runtime guarantees me 20+ hours of 3G broadband and week-long phone use. Being barely bigger than a Blackberry, I can effortlessly stash the XP8000 on my belt, and charge my smartphone while I walk.

    The XP18000, on the other hand, was a huge disappointment. Using a Toshiba NB305 netbook, it was incapable of recharging the factory 6-cell battery while powered on, and could not provide 2 full charges while powered off. For my usage scenario, that's a failure, as I plug in the external battery when my netbook hits 3% critical, right before Windows does a force shutdown, allowing me to continue working.

    Using this deplete-charge-deplete approach SHOULD allow me 14+ hours of continuous power-on time, except that even the beefy XP18000 couldn't get through 1 netbook charge. Had it been capable of providing one full charge powered on, or two full charges powered off, I would have recommended the XP18000 as well.

    http://lgponthemove.blogspot.com/2010/07/accessory-corner-3-energizer-xp18000.html
    Reply
  • a_fortiori
    Nice article. I wonder if these units can be used as a mini-ups for equipment like a NAS, routers and modems. It would be great if you could wire these with the NAS, and be sure that a power outage wouldn't damage the NAS. Considering that the NAS units typically consume much less power than a notebook, these should be able to cover 4-5 hrs of power outage (?) Any thoughts?
    Reply
  • shineon2010
    Very good info , alot of products that im having second thoughts about.
    Reply
  • junixophobia
    shineon2010Very good info , alot of products that im having second thoughts about.
    Just buy an automatic inverter that works for hours with a car battery
    Reply