Sign in with
Sign up | Sign in

Hitting The Highway Or Traveling By Air

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

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.

Ask a Category Expert

Create a new thread in the Reviews comments forum about this subject

Example: Notebook, Android, SSD hard drive

Display all 17 comments.
This thread is closed for comments
  • 0 Hide
    shreeharsha , September 2, 2011 7:08 AM
    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)
  • -1 Hide
    randomstar , September 2, 2011 2:57 PM
    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"!
  • 0 Hide
    JohnnyLucky , September 2, 2011 3:43 PM
    It's a shame that there is no single International standard to go by. It would make things a lot simpler.
  • 0 Hide
    cadder , September 2, 2011 3:46 PM
    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.
  • -1 Hide
    soccerdocks , September 2, 2011 5:21 PM
    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.
  • 1 Hide
    legacy7955 , September 2, 2011 5:40 PM
    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.
  • -1 Hide
    mayankleoboy1 , September 2, 2011 6:34 PM
    thats another lame article consecutively.
    come on Toms, get the BD benchies out already.
  • 1 Hide
    CaedenV , September 2, 2011 7:43 PM
    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.
  • 0 Hide
    Anonymous , September 3, 2011 12:26 AM
    only quake 2.
  • -1 Hide
    simontay1984 , September 3, 2011 3:21 AM
    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.
  • -1 Hide
    madjimms , September 3, 2011 11:18 PM
    Rosewill makes some very good laptop bricks.
  • 0 Hide
    cybersans , September 4, 2011 4:52 AM
    the problem always created by U.S.A. they like to twist the ISOs upside down. for example, metric system, kilometer become miles, centimeter become inches, kilogram become pound, standard road direction is left,they changed to right. wall socket pin, voltage. etc. and today, they corrupted world financial system, caused loss of multi billion to several region. if they follow the a-long-lone time ISOs, it will be easier to everyone in this world.

    cheers!
  • -1 Hide
    Anonymous , September 4, 2011 9:17 PM
    @Cybersans. The United States customary system of measurement is based on imperial units, which were used in the British Empire. Most intelligent people in the world, that have studied at least some history, understand that the United States of America was born from 13 British Colonies. That being said, many customs that are still used in the US today were born from our British Heritage like for instance the mile and the ENGLISH LANGUAGE!! Most of us, who celebrate that heritage, also feel a requirement to come to the aid of the nation in which fathered our own in say, ‘times of crises’ which is another history lesson. Also, since most of the technology that is discussed on this website was created in our country, it is only customary that the technology gets measured in its country of origin not matter how convoluted it may be. Cheers!
  • 0 Hide
    WyomingKnott , September 7, 2011 6:24 PM
    legacy7955Actually 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.

    Phones and GPS devices take less current to charge than notebook batteries. These devices are moving from proprietary chargers to charging via USB. I haven't met a notebook computer yet that could charge off the low USB currents, even if the 5V supply could be pushed up to 12V.
  • 0 Hide
    WyomingKnott , September 7, 2011 6:29 PM
    Quote:
    he battery in the notebook largely regulates the trickle charge, even when it's topping off from a constant current/constant voltage charging scheme.

    I hope that that is so; it certainly wasn't the last time that I looked at this in detail. At that time, just putting 15V across the charging terminals of the battery and going to sleep would ruin the battery; there was all kinds of logic in the charger to protect the battery.

    Have they really built this into the batter now, so that all we have to do is provide a DC source with the right voltage and no other control circuitry?
  • 0 Hide
    kishan somaiya , September 15, 2011 5:50 PM
    i don't think this new product will give fruitful solutation
  • 0 Hide
    arlord , September 9, 2012 2:38 PM
    i think this price is too expensive, $80 in