Universal Laptop Power Adapters For The Air, Road, And Wall

Hitting The Highway Or Traveling By Air

If you are hitting the highway and you need a way to keep your notebook charged, a simple power inverter might be the cheapest way to go. And it's really the only alternative for those disinterested in paying for a travel adapter.

There are a handful of drawbacks to buying an inverter rather than a new adapter. Most cars come with a 90 A alternator, so there is plenty of power to output (amps * volts = watts). However, the alternator isn’t your main limitation. First, there's the fuse used to protect the circuit. Most automotive fuses limit the output on the cigarette lighter to 15 A. More constricting is the cigarette lighter receptacle itself, though.

The 12 VDC connection in almost every car's cigarette lighter is governed by standard J563 of the Society of Automotive Engineers. Not only does the standard specify dimensions, but it also caps maximum current at 8 A. Do the math, and that's 12 V * 8 A = a maximum of 96 W.

The figure assumes the cigarette lighter is on a dedicated circuit with a 15 A fuse. In the real-world, you're going to have less current because (at least in the handful of vehicles we were able to check) the cigarette lighter shares a circuit with the radio. Now, you shouldn’t run into any problems if you're powering a full-sized notebook. But if you wanted to wire up your desktop machine, you'd need a dedicated circuit with separate fuse.

No matter what, this isn't an ideal implementation, though. Your car already supplies a DC voltage. When you use a power inverter, you convert that to AC. From there, you plug in your original notebook’s power adapter to get back to DC. Simply using a travel adapter lets you go DC-to-DC, which is always going to be more efficient.

Most auto ignition systems have four positions: On, Start, Accessories, and Off. Start is spring loaded to start your engine, and Off is self-explanatory. Acc, or Accessories, turns on electrical subsystems that don't require the engine to run unnecessarily as a convenience, such as the radio and windshield wipers. On turns on all electrical subsystems necessary to start the engine.

If you use your notebook via an inverter while driving around town, you're in fairly good shape, aside from the previously-mentioned inefficiency and the unsafe distraction. Your battery gets charged by the alternator when the engine is running. Driving a notebook with an inverter with the ignition in the Acc or On positions is a far worse idea, though. You waste a lot of energy with the DC to AC to DC conversion, which puts a real load on your battery. Drain it too far and you'll damage the cells beyond the point of charging back up again. At that point, you may as well have spent the money on the travel adapter we recommended earlier on.

Incidentally, this is also why you generally can't use inverters on airplanes. The EmPower outlet outputs 15 V DC at a maximum load of 75 W. As a result of that efficiency problem, you might find it difficult to get ample power from that connector.

Every conversion you add to the circuit results in a loss of power efficiency. So, travel adapters have a non-inverting DC-to-DC converter to get from 12 V / 15 V to the voltage of your laptop.

  • shreeharsha
    I actually thought they are going to release a standard for all the Laptop Power Adapters, one power adapter for all the notebooks. (only might be different wattages)
  • randomstar
    I can not honestly tell you the number of friends, customers, and others that bought a non-dell power adapter for a dell unit, and found out that it will run the unit, with reduced performance, but will not charge. and paid lots of money. I keep a collection of actual dell power supplies 65w, 90w, 120w ,just to help out when that happens. funny thing , if you shop around you can get the real ones for less than the kingston, etc "universal"!
  • JohnnyLucky
    It's a shame that there is no single International standard to go by. It would make things a lot simpler.
  • cadder
    And even worse than that- between my daughter and I we've owned 3 Dell laptops, and each one uses a different power adapter and plug.
  • soccerdocks
    cadderAnd even worse than that- between my daughter and I we've owned 3 Dell laptops, and each one uses a different power adapter and plug.
    That seems unusual. In my house we have 3 different laptops spanning 6 year purchase dates and they all have the exact same plug. Two of the laptops are Latitudes and the other is a Studio XPS. The only difference is that the Studio XPS came with a 130 watt adapter as opposed to 65 watt adapters for the Latitudes. So no gaming with that machine while plugged into the 65 watt adapters.
  • legacy7955
    shreeharshaI actually thought they are going to release a standard for all the Laptop Power Adapters, one power adapter for all the notebooks. (only might be different wattages)
    Actually this sort of standard DOES exist in Europe for smart phones and cell phones, I'm not sure if it includes laptop or netbooks but it might. I'll have to search around.

    It seems the bottom line today is buy the OEM adapters if you want to play it safe.
  • mayankleoboy1
    thats another lame article consecutively.
    come on Toms, get the BD benchies out already.
  • CaedenV
    This is exactly why I don't understand dropping serious money into a laptop. Have a good desktop, and a cheap laptop/netbook/smartphone/tablet for your portable needs. Batteries only last 2-4 years with consistent use, so after 2-3 years you need a $150 battery, plus if your power brick is worn out then it is another $120 for that...
    So that $800 laptop then requires another $270 to run after 3 years? And this is assuming you don't drop the thing, or break it through normal wear and tear. And laptops do not age as gracefully as desktops because they are generally crap hardware to begin with. Much better to stick with a $300 laptop, and a decent desktop. The desktop will keep up with the times longer and will have less maintenance, while the laptop can be swapped out when need be.
  • only quake 2.
  • simontay1984
    My Toshiba Satellit Pro M30 is over 5 years old now and it still works fine. HDD and RAM has been upgraded. The battery went flat a long time ago and won't recharge.
    Instead of buying a new Lithium-Ion batt (that would only last about another 2 years anyway), I just use a 12V 7.2Ah Lead Acid connected to the PSU input when I don't have access to a mains supply for an extended period (e.g. on long train journey).

    It works cos the PSU output voltage is 15V so 12V is close enough.