Saturday, January 24, 2009

Dell XPS M1530 Slim Power

Review: Dell's "Slim" Laptop Power Supply is a well-designed product that makes for a great second power-supply and it works with a variety of (Dell) laptops, using A/C, car or Airplane adapters. Near the end is a discussion on the "center-pin" which makes Dell's AC adapters proprietary (much like HP and Sony).

Note: If you are looking for a simple replacement power supply, without all the goodies, see Dell Slim Power Adapter on Amazon (This is an A/C only; Dell-branded adapter, which is not reviewed here. This adapter includes the infamous center pin) See also this Keyliner third-party battery review.

When I need the laptop on the road, I have to reach around the desk, unplug the power cord and then wrap or stuff the cord into the bag. When I get home I have to unwrap it and set everything back. This is a minor nuisance, but a nuisance none-the-less. I've long wanted a second power supply that would stay permanently in the bag.

Dell offers two power adapters for the XPS, Latitude and Inspiron laptops. You can buy the original 90-watt power brick or you can get the 65watt "Slim Combination Adapter." After reading the reviews on Dell's site, I decided to try the slim version, even though several reviewers had problems.

What I found was a great kit that works well and I am recommending this as a second, traveling power adapter. It is particularly nice to have all of the different types of power connectors in one kit.

  • By itself, it is smaller and lighter than the original
  • Car and Plane adapters
  • Multiple length configurations; 2ft long to 6ft.
  • Can be made even longer at Radio Shack
  • Powerful enough to charge while using

The adapter is considerably smaller and lighter than the original, provided you don't carry all the accouterments.

Cord Lengths:

The total length of the power cord varies, depending on which of the optional cables you attach. This takes a moment to explain. At one end, it comes with two detachable power cords: a short 8" length cord and a slightly longer 2ft plug.

On the other side of the brick, it has a permanent 12" dangly-cord that can plug directly into the laptop or you can connect a 3ft extension to make it longer. By combining these cords in varying orders, you can adjust the total length from 2, 3, 5 and 6 feet long.

This is a creative design but does involve more cables than normal. When configured at its shortest length, the entire length is only 2ft long (see top illustration) and it is so short that I questioned its usefulness, but it has been handy at the office, library and kiosks where power is at desktop level.

Too Short? Easily Fixed:

At the other end, with all the extensions attached, many have complained the 6 foot (2M) length is too short, which I can agree with. Fortunately, the plug-end of the adapter uses a standard appliance-cord and you can buy a 6'ft cable at Radio Shack for $6. I personally use this cord, making the total length 10ft. (Important Note: When buying a new appliance cord, be aware there are 4 different end-plug shapes -- and all are called appliance cords; bring your 2' cord to the store to make sure the ends match -- Isn't it amazing they couldn't standardize this)

The kit also comes with a car-adapter, an airplane Empower-adapter, as well as a small bag to carry everything. Everything was thoughtfully designed, but there are a lot of pieces.


Packing all of the extra goodies is messy and you will need the bag (included) to organize everything. The unit does not have built-in cable-straps so you will want to buy extra velcro straps.

Mixed Reviews:

Web-reviews on Dell's site are decidedly mixed. Several people complained about the 65watt power supply being so weak that it could not simultaneously power the laptop and charge the battery. I have not seen this problem and I often use this adapter to charge my batteries while I am using the machine. (See note below on a possible benefit)

Other complaints are about the total cord-length being too short, but like I said above, this is easily fixed with $6 and a trip to Radio Shack. If you buy this kit, buy the extra cord.

Some have also complained the adapter is "hot." I have not noticed anything unusual here. For a living, power adapters convert excess 110V into heat; that is what they are supposed to do.

Finally, when purchasing, use Dell's site to confirm your laptop model is appropriate (or look at the technical specs below). Dell's site shows the supply is compatible with a variety of Dell laptops, but several have posted the plugs do not fit. This may be due to changes in Dell's laptop lineup or it may be a flaw in their application charts. Hold Dell accountable for this by taking a Print-Screen when you order.


Price: $90.00 ($10.00 more than the standard adapter. Available on Dell's website: see Laptop Accessories). You will also need to buy a longer power-cord from Radio Shack ($6), plus Velcro straps to tie up the cables when you don't want to use the included bag. I no longer carry the bag unless am on a road or plane trip.

BIOS Warning:

After using this power adapter for nearly a year, one day the laptop mysteriously announced, during a cold boot, with this BIOS message: "Warning: a 65W AC power adapter has been detected, which is less than the recommended 90W adapter." This is a given, because by definition, it *is* a 65 watt power supply. I pressed F3 (as prompted), to disable the message. I have had no concerns or repercussions about this message.


In summary, this is a neat device and it makes throwing the laptop in the bag a non-event. I have now used it for over a year and am still pleased. As a bonus, the car adapter lets me watch movies while driving. Link

Other Branded Adapters

It appears that all new Dell AC adapters are proprietary and you may be forced to use them, for reasons discussed below. Other vendors sell competing products. Belkin and Kinniston sell small power adapters, designed for laptops and they often include a variety of plug-adapters so they will fit any machine -- but these kits do not have auto or plane adapters. And, most importantly, they are missing a center-pin (details below).

My opinion: The Dell adapter, as expensive as it is, works. Spend the money and you won't have to hassle with this again.

Technical Specs from Dell:
Note unusual center-pin (thin, fragile wire); see below.

Center-Pin Notes on Dell Powersupplies:

Dell power supplies (as well as Dell, Sony and others) have a center "Smart-pin" (see the schematic, above). Dell has not been forthcoming about the purpose of the pin, but it apparently transmits a code to the motherboard, telling the laptop what type of power supply is connected and the wattage.

Most have assumed the center-pin is a nefarious feature, designed to prevent third-party knock-offs, but with the comments this article has received and other research, the pin appears to have a legitimate purpose. Read on for the details.

Inside the Power Supply unit itself is a small circuit board that encodes the wattage, brand and other (proprietary) information. If the laptop does not receive the proper signals, or if the center pin is damaged or broken, the laptop assumes the worse and will not use the circuitry to charge the battery; it will, however, run the laptop off the AC circuit.

The issue apparently comes down to this: Dell, Sony and HP have all had massive recalls where batteries overheated and caught fire. Some of this was caused by improper (third-party chargers) and by defective batteries. Manufacturers, in order to fend off more lawsuits, made these new chargers with these very conservative features. All new laptops, not just Dell, now have similar circuitry. Until the industry standardizes on chargers, and their plugs, all vendors are forced to make their power-supply units proprietary.

There is no work around. Despite what other articles have said, a purported BIOS-workaround will not resolve this problem (at least not on the M1530).

Some have also reported that while plugged in (without a center pin), the laptop may run at a reduced speed; I have not been able to substantiated this. (Determine laptop speeds with this link: Intel) See this helpful Dell Forum article.

For hairy details on the proprietary circuitry, see this fun eeprom programming article. In addition to the forum comments, I have condensed other comments here:

"You've discovered the third power supply connector for modern Dell (and HP) laptops. [This is called a "smart pin"]. This third lead is used for communications between the power supply and the laptop and [apparently reports the power capacity and brand-name information]. I have no idea what the communications protocol between the two is, but I know Dell laptops will reduce charging current (and extend charge time) when operated with 65W instead of 90W power supplies..." [TRW comment: when working properly, charging time may be reduced because the slim adapter is 65W instead of 90W. I suspect if the third-pin is not transmitting, the laptop will assume a lower wattage in order to protect the equipment?]

When using a non-pinned powersupply, BIOS will report an "Unrecognized Power Adapter." I also had a reply this evening on a Dell sponsored forum that one can disable such messages in the BIOS 'Adapter Warnings: Enable/Disable' option. (I now believe this suggestion does not work or may not work on newer Dell laptops.)

Here is an interesting and very geeky article on what is being transmitted along that center pin Link.

Additional Comments:

In this article (Dell XPS M1530 Replacement Battery), I discuss how the battery has been failing. One of the rumors is Dell charges the battery too quickly and the battery heats up more than it should. I've pondered this thought: Using the slim power-adapter might charge the battery more slowly and help preserve the battery's life? Comments?

Related articles and links:
Review Dell XPS M1530 Laptop
More on the Dell XPS M1530
XPS M1530 Replacement Battery
Laptop Battery Care and Feeding Dell Slim Power Adapter on Amazon (A/C only)