If you consider yourself to be a road warrior, you need a way to keep your notebook running when when you're away from a wall socket. And that's regardless of whether your primary battery has the chops to keep you operational all day long. Put simply, most folks can't count on a day's worth of up-time. So, it's important to have a solution in place for putting a bit of pep back into your mobile platform during your afternoon siesta.
What do you need in order to keep your notebook fully functional? If you're in a car or on a plane, you need a cigarette lighter receptacle or an EmPower plug, along with a compatible power adapter. Most system vendors (like Dell and Lenovo) offer travel adapters, but they can get pretty expensive. Worse, they aren’t always compatible with multiple generations of products.
Lenovo 90 W AC/DC Combo Adapter (P/N: 41R4494)
For example, when IBM moved from 16 V to 19 V, timed to coincide with Intel's Pentium-M to Core 2 Duo transition, the company adopted a different plug size. That meant the older AC/DC combo adapter (P/N: 73P4502) wouldn't work with the newer hardware. Owners of more recent Lenovo notebooks can use the current AC/DC combo adapter will find that it's backward compatible through the use of a different plug tip.
Traveling Headaches
If you travel overseas, you probably use plug adapters as well, since AC sockets differ from one region to the next. Currently, most system vendors arm their mobile offerings with 110-240 V power adapters, which means that they're universally compatible, so long as you have the right wall connector. A notebook sold in the U.S. might include the same power brick as one in Europe, but they two systems will come with different power cords.
If you're traveling abroad with a power adapter that isn't 110-240 V-capable, there's a good chance you need a voltage converter or an entirely new brick, depending on where you're going. Travel adapter kits for cars and trains cost up to $100. So, if you aren't interested in making that investment, a power inverter is your only other course of action. Planes are another matter entirely.
There is no universal power plug standard used within the travel industry. Even in a single airline's fleet, the same model of plan might use different plugs depending on its configuration. For example, there are four different 737 configurations flown by Alaskan Airlines; one uses cigarette lighter receptacles and one employs the EmPower connector.
Frayed Power Cables

As notebooks get older, it's common to encounter fickle power adapters. Over time, plugs and connectors start exhibiting quirks. We've seen cords that have to be held a certain way to maintain a connection. We've seen others that simply stop charging the battery altogether. Few of those problems are do-it-yourself fixes. More often, the easier alternative is simply buying a new adapter.
From there, you can buy a straight replacement from your system's vendor. Or, you can go with a third-party solution. With a replacement, you know what you're getting. But a third-party's solution might include more features. It's a tough call, really. Before you go the third-party route, know that using non-factory equipment could very well void your machine's warranty, if it's still covered.
Asus says that, as long as the third-party adapter supports the right input/output voltage and power specs, your warranty remains intact. If the charger doesn't closely match the original adapter's specs, though, and damage occurs, the company may not honor your warranty. The reasoning is sensible. It would argue that the damage might have been caused by another company's power adapter, though it isn't clear how closely the third-party hardware would need to come to Asus' original equipment.
According to Dell, "all Dell-branded power adapters have to pass the Dell qualification process and necessary system-level certification." This means that only power adapters supplied by Dell or included with a Dell-branded solution are covered under the company's warranty policy. If damage occurs as a result of using a third-party adapter, your notebook isn't covered.
So, Where's The Problem?
Most AC adapters feature an LED built into the power brick. As you might imagine, this serves an actual purpose. If you plug in your notebook and that light doesn't turn on, something is wrong.
Most AC adapters come as two parts: the AC cable and the DC power brick/output cable. If you aren't getting power, and you don't have an LED or a two-part adapter, there are some steps you can take to check for damage. Obviously, you should only follow these steps if you have experience with power equipment and already know what you're doing.
First, set your multimeter to measure AC voltage. If your power adapter comes as two parts, disconnect the AC cable from the power brick and make sure it's plugged into the wall socket. Attaching the test leads to the AC cable, you should get a reading close to 120 V. Be careful when you do this; the two test leads should never come in contact with one another as current passes through them.
In order to test the DC side, set the multimeter to measure DC voltage, similar to the picture above. After reattaching the power brick and AC plug, check the voltage by touching the inside and outside of the connector.

Usually, you'll find a diagram on the wall wart that illustrates the positive and negative contacts. If your adapter doesn't have this, most manufacturers expose negative polarity on the sleeve and positive polarity in the center. If your connector includes a center pin, ignore it. Dell uses that pin to transmit a signal that verifies whether the adapter is one of its own or not. Other manufacturers use it to center the plug. Most of the time, the inner and outer sleeves are the parts of the plug that actually carry current.
If you aren’t getting a reading on the AC cable, you might just need a new cord. An auction site could be your solution there. If you aren’t getting a reading on the DC side, there's a good chance that you need to replace the entire brick.
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.
Universal power adapters are unlike the power adapter that ships with your notebook. The most obvious difference is that the aftermarket adapters include a variety of tips. Each tip has a unique fitting to accommodate as many manufacturers' hardware as possible. Vendors use a range of voltages, and varied sizes help prevent connectivity between incompatible components.

Even within a single brand you'll find notebooks that use different voltages and plug sizes. For example, Dell has a standard plug size, but the Inspiron Minis don't follow it.
Here's another difference: the stock power adapter that ships with your notebook supplies voltage at a fixed setting. This is not the case with universal power adapters. In order to satisfy the multiple voltages required of different devices, they must be capable of outputting different voltages as well.
Tip Set from Duracell's Universal Adapter
The switching mechanism is in the tips. Inside any given tip, there is a sense resistor that has variable resistance to the current supplied by the power adapter. This resistor drops the voltage as the current crosses its path. The small voltage drops are then fed to a simple comparator circuit, which then is used to further control the DC output from the power supply.
| Tip # (Targus) | Voltage | Pin 1-3 resistance (kΩ) | Pin 1-4 resistance (kΩ) | Connector ID (mm) | Connector OD (mm) | Connector length (mm) | Systems |
|---|---|---|---|---|---|---|---|
| L111 | 19.0 | 5.8 | 85 | 1.7 | 5.0 | 10.8 | Compaq, HP |
| L105 | 16.5 | 13.9 | 168 | 2.5 | 5.5 | 11.1 | IBM (older T4X connector) |
If you take measurements from the tips themselves, you'll notice the difference in resistance output. Pins 1 and 2 supply power to the computer, and we've numbered the pins from the center pin in the connector. Pin 1 is negative and pin 2 is positive. These measurements are unique to the tips, not the adapter.
With the technical explanation out of the way, let's compare three universal power adapters.
Duracell is now a registered trademark of Procter & Gamble. While Duracell is branded on this adapter, this is not a Duracell product per se. It is actually manufactured under license by Battery-Biz. The company supplies the majority of Duracell's product-specific batteries and power products, such as car inverters. If your product has "Duracell" plastered on it, but it isn't a watch, AAA, AA, C, D, or 9 V battery, there's a good chance Battery-Biz makes it.
This charging kit covers the three basic modes of travel: the air, in a car, and when you have an AC outlet handy. It also happens to be one of two universal adapters sold under the Duracell brand. Covering that trio of bases costs about $90, which is about $20 more than the 90 W model with the cigarette lighter receptacle plug on its own. There's also a 40 W adapter, but that's specifically for netbooks.
The adapter includes Velcro strips for cable management, but you're going to end up with a corded mess one way or the other. The cables that connect to the power adapters aren't angled, making them difficult to pack away. And although this is one of the few adapters that actually includes an EmPower plug, there is a very faint high-frequency squeal that emanates from the adapter when it's used with certain 16 V notebooks.
While Duracell backs this up with a three-year warranty, nobody likes dealing with the RMA process for silly manufacturing deficiencies. The problem seems to disappear when we use the adapter with 19 V notebooks, so the problem could be related to the sense resistors responsible for lowering the voltage.
The Premium Laptop Charger AC/DC (APM69US) is actually more like a kit than one specific charger. Targus simplified its product lineup to be somewhat modular. The Notebook Charger AC (APA70US) and Compact Laptop Charger AC (APA69US) all share the same 90 W power brick as the APM69US. The APM69US (which runs $122) is simply a combination of what you get in those other packages. The difference is that the APA70US and APA69US don't come with automotive adapters. The APA70US is specifically for netbook owners; you only get a netbook adapter tip and the USB tip. The APA69US is the same, but comes with all the tips also provided with the APM69US.
Meanwhile, the APD80US is the car-only version of the kit. There is no power brick for AC input, but you get all the same adapter tips as the APM69US and the APA69US. The cheaper Netbook Charger (APA72US) shares the same output cable and tip system, then substitutes in a 45 W power brick for the 90 W version. This is the same 45 W charger that comes with the Charger for iPad (APA7201US). The difference there is that you get an iPad tip instead of a set for netbooks. All of these kits still come with a USB tip, so you can charge your cellphone or eBook reader at the same time as the main device.
The best thing about the APM69US is its cable management system. The kit includes a highly elastic cable tie that keeps everything nice and neat, though you still need to deal with the power brick separately. If you're plugging in multiple devices, there's also a caddy that clips onto the cable and secures an extra pair of tips.
Targus advertises this charger as an Automotive/AC/Airplane charger, but it doesn't come with an EmPower plug. This means you can only use the adapter if you're in an airplane with a cigarette lighter-style outlet.

If you need EmPower connectivity, you have to buy an adapter, which usually runs ~$10.
Kensington is the only company that advertises a "travel adapter" without automotive support. Its previous K33197US was the last Auto/AC/Air combo adapter. Now, the only way to get something that works in the car is with an EmPower-to-cigarette adapter (like the one that comes with the Duracell charger).
Otherwise, if you stand by Kensington's products, you're compelled to buy a power inverter instead (and we already know that's not an ideal solution). The EmPower-to-cigarette outlet adapter is quite hard to come by. Frankly, Kensington should just throw that adapter into the mix, as it already includes it with the K38037US power inverter.
While it's true that this charger is the cheapest of the bunch (~$88), it has a few limitations. The USB port is oddly placed off to the side, which complicates cable management if you prefer to keep the adapter in your bag and spool the power cord. Additionally, this adapter is the only one we're testing with limited voltage output. Instead of determining voltage range based on sense resistors inside the connector's tip, it employs a pin-out system.
There are two SIM-like plastic cards that come bundled. In order to achieve a specific voltage, you need to plug one card into the spring-loaded receptor slot. The 16 V card provides a voltage output between 14-17 V, while the 19 V card outputs between 17-21 V. It seems like Kensington is tiering the voltage output as an additional safety mechanism.
At the same time, you could unintentionally create a problem by using the wrong card, as you'd either get too much or too little voltage. In the case of the former, you could cause real damage to your notebook.
Duracell's compatiblity chart from Amazon
Will these adapters work with your notebook? That's hard to say definitively. Duracell doesn't publish a compatibility list on its Web site. Fortunately, if you hit Amazon, you'll find a small chart listing brands and corresponding tips.
The back of the box spouts off a list of models, but that's no compatibility guarantee. There is a more complete list published in the included manual, but ideally, you'd know whether the adapter works with your notebook before you sink the cash on it. Well, we went ahead and scanned those pages so you can see for yourself.
Kensington is just as vague, though you can find a compatibility list on its Web site. Again, that's hardly a clear-cut matrix of models, though.
Inside Flap of Targus' Retail Box
Targus publishes a short-hand compatibility list on the inside flap of its retail box, but the company's Web site is much more helpful. There is a guided search, similar to Kingston's and Crucial's memory configurator, that tells you exactly which adapter tip you need for your laptop and if it's offered.
If your notebook happens to be from one of the top four vendors (Acer, HP, Dell, Lenovo), you probably don't have anything to worry about.
We recently took a 2000 mile road trip, and then flew back, allowing us to run a couple of benchmarks in hotels, a Jeep, and up in the air. Even though our test vehicle was limited by its 15 A fuse, that was more than enough current for Duracell’s 175 W Pocket Inverter. We tested the charge time from 0% with wireless networking disabled, using the lowest display brightness setting, and playing back a DivX-based movie.
| Time to 100% Charge Dell Vostro 3300 HH:MM:SS | Duracell 90 W | Targus 90 W | Kensington 90 W | Stock 65 W Dell Adapter |
|---|---|---|---|---|
| From AC | - | 2:05:32 | 2:03:55 | 2:05:25 |
| From Car | - | 2:05:55 | 2:03:21 (EmPower-to-Cigarette Adapter from Duracell kit) | - |
| From Car using 175 W Duracell Inverter | - | 2:02:57 | 2:05:34 | - |
| Time to Charge from 5% to 10% Dell Vostro 3300 HH:MM:SS | Duracell 90 W | Targus 90 W | Kensington 90 W | Stock 65 W Dell Adapter |
|---|---|---|---|---|
| From AC | - | 00:5:00 | 00:04:20 | 00:04:05 |
| From Car | - | 00:05:10 | 00:04:10 (EmPower-to-Cigarette Adapter from Duracell kit) | - |
| From Car using 175 W Duracell Inverter | - | 00:05:00 | 00:04:35 | - |
| From Plane using Cigarette Plug | - | 00:05:00 | 00:04:15 (EmPower-to-Cigarette Adapter from Duracell kit) | - |
Charging times are a double-edged sword. Ideally, you want a nice slow charge so that your battery lasts more than a few hundred charges. Fast charge times keep you away from the wall socket longer. but, in the long run, they cut down on the battery's health, too. Manufacturers utilize a variety of charging schemes to strike a balance. Usually, the rate of charge starts slowing down somewhere in the 80% to 95% range, which is why the charging time from 0% to 10% is faster than 90% to 100%.
Surprisingly, there is no difference between the three adapters, at least to charge to 100%. The battery in the notebook largely regulates the trickle charge, even when it's topping off from a constant current/constant voltage charging scheme. When you look at the charge from 5-10% (the only test available on the plane, given available time), Targus' Premium Laptop Charger seems to take a more cautious approach for the faster leg of the charge.
Using the Vostro 3300, we couldn't get the Duracell charger to work. It is the only charger of the three we tested that doesn't transmit an identification signal over the center pin. As a result, you can only power a Dell-based notebook; charging is completely disabled. There is no resolution to this problem, which you might experience if you buy your adapter on Ebay for a Dell notebook. Furthermore, you can't use a power inverter in tandem with the stock power adapter, and we're not sure why.
As a result, we had to run an additional benchmark using a 13.3" MacBook Pro to test the charging time of Duracell's charger compared to the other two. We ran it at maximum brightness, wireless enabled, and a custom benchmark for web browsing that mirrors our earlier RLUMark.
| Time to 100% Charge Apple 13.3" 2010 MacBook Pro HH:MM:SS | Duracell 90 W | Targus 90 W | Kensington 90 W | Stock 60 W Apple Adapter |
|---|---|---|---|---|
| From AC | 03:00:40 | 02:53:50 | 02:55:40 | 02:55:40 |
Overall, the Duracell product is basically the same flavor of laptop charger as the other two. Aside from its price, the main differences are found in its advantages. Duracell offers a three-year warranty compared to Targus' two years and the one-year coverage from Kensington. With that said, only Targus offers "Free Tips for Life." You simply have to pay for shipping on a tip that doesn't come with the original set ($5 for UPS Ground, plus tax if you live in California).
We wanted to throw in a benchmark from a generic Ebay charger, but the one we bought off some guy in Hong Kong died two days into testing. That goes to show that you get what you pay for; buy generic power equipment and you're putting the purchase and whatever it's connected to at risk. Sounds like reason enough for us to invest in a solid adapter, if we're going to buy anything at all.



















