"It seems like a dead wire leading nowhere."

September 2, 2014 7:18 PM

How does a Dell laptop know what kind of power adapter is connected? The adapter tells it. Reverse-engineering: Hacking the Dell laptop power adapter 1, 2, 3, 4.
posted by We had a deal, Kyle (46 comments total)

So all this is just so the laptop knows how much wattage to draw? Why not just make the 65 watt connector a different shape than the 90 watt connector?
posted by mccarty.tim at 7:26 PM on September 2, 2014

Why not just make the 65 watt connector a different shape than the 90 watt connector?

My old Dell could actually work with either. It just charged much slower with the 65 watt one. My friend had a different Dell computer with a hexagonal connector which was pretty annoying when I tried to borrow his charger.
posted by BungaDunga at 7:30 PM on September 2, 2014 [2 favorites]

Is 'optimal system performance' the same thing as 'more magic'?
posted by RonButNotStupid at 7:32 PM on September 2, 2014 [6 favorites]

I, uh, wasn't expecting the hanging bollocks.

Nobody expects the hanging bollocks.
posted by w0mbat at 7:32 PM on September 2, 2014 [5 favorites]

I, uh, wasn't expecting the hanging bollocks.

NOR WAS I. They didn't appear on any of my previous visits. (For the curious, and after refreshing that first link a few tens of times: one of the banner images is this one.)
posted by We had a deal, Kyle at 7:32 PM on September 2, 2014 [3 favorites]

ERROR 403 - FORBIDDEN

Chrome does NOT want me to see bollocks.

/derail, back to the tech talk!
posted by joseph conrad is fully awesome at 7:34 PM on September 2, 2014 [1 favorite]

Somebody should really sell a little dongle to go between a Dell laptop and any off-the-shelf charger. For bonus points you could make it programmable, to report anything you wanted/needed.
posted by Joe in Australia at 7:48 PM on September 2, 2014 [2 favorites]

Invisible Green Time-Lapse Peloton: "Anyway, the new Dells are shipping with much lighter and smaller chargers, thankfully. "

I've noticed this with HPs, too. I have a newish Folio, and the charger is like 1/3 the size of the charger on the couple year old Elitebook my kids use.
posted by Chrysostom at 7:56 PM on September 2, 2014

More dangle than dongle
posted by fallingbadgers at 7:57 PM on September 2, 2014 [2 favorites]

Thanks! This was a fun read.
posted by phooky at 8:09 PM on September 2, 2014 [1 favorite]

Lenovo has been doing this for years. The 90 watt supply for a W500 will run a W510 whose native adapter is 135 watts, but the CPU throttles down to a spartan clock cycle and it takes forever to get anything done.
posted by CynicalKnight at 8:13 PM on September 2, 2014 [2 favorites]

Pretty neat!
posted by ph00dz at 8:22 PM on September 2, 2014 [1 favorite]

Somebody should really sell a little dongle to go between a Dell laptop and any off-the-shelf charger. For bonus points you could make it programmable, to report anything you wanted/needed.

Which is what he did in the final blog post.

However charging protocols, rates, and endpoints for a given battery/cell type and construction - as well as the power available from the internal converters to supply the CPU, etc - are all fairly heavily dependent on the available supply voltage and current capacity of the charger.

Giving people the ability to lie about what the charger can actually provide simply leads to worse performance (e.g. CPU throttling, as CynicalKnight mentions) and reduced battery life (since the battery is likely to be repeatedly under/overcharged.

p.s. Not every 3-lead component is a 'transistor', and the 20meg resistor & 'diode-like device' the second blogger ponders (but fails to understand) is the very static protection he thinks is missing…
posted by Pinback at 8:26 PM on September 2, 2014 [6 favorites]

Never Mind The Bollocks.

I don't understand why Dell does this. It is unnecessary complication. I can't see that this has any useful function except as a sort of DRM, requiring you to use only Dell replacement parts.
posted by charlie don't surf at 8:39 PM on September 2, 2014 [6 favorites]

I sort of guess it lets them use one size plug and have power supplies of varying power outputs? It prevents the computer from browning out by drawing too much current or starting a power supply fire? Maybe?

I dunno.
posted by GuyZero at 8:45 PM on September 2, 2014

Dell-laptop-charger-interchangeability is outrageously useful in an enterprise environment--especially education. I do IT in a school district that contracts (nearly) exclusively with Dell, and the ability to just take any laptop charger I have lying around and charge any laptop I have lying around, regardless of which cycle the gear rotated in from, is an immense time and money saver.
posted by Joviwan at 8:53 PM on September 2, 2014 [12 favorites]

Same thing with the Macbook Pro/Macbook Air chargers - you can trickle-charge a Pro with an Air charger, and you can trickle-charge a MS Surface Pro with a Surface RT charger, etc.

Usually if you've got a system that requires $X watts, you can use it (but not use AND charge at the same time) with a charger designed for $X-Y watts if the connectors are the same.

This is often handy when the "weaker" charger is much cheaper than the full-power charger and you just want to have an emergency spare available (to keep at work, etc).
posted by mrbill at 9:32 PM on September 2, 2014

This is often handy when the "weaker" charger is much cheaper than the full-power charger and you just want to have an emergency spare available (to keep at work, etc).

I will admit i'm fairly bitter about magsafe 2. I have a stockpile of various wattages of old magsafe chargers, going back to the first macbook i got in ~2008. They're actually pretty readily available for ~$5 at thrift stores. I was figuring i'd probably never have to buy another spare again, just keep the ones i had indefinitely... and then magsafe 2 came along. Yea there's that stupid adapter thing, but that's easy as hell to lose and also seriously?

I've noticed that some of the newer thinkpads have strayed from the old grey barrel connector too.

At least dell seems to be staying the course. The only real complaint i have about them, is that like the older apple chargers they just fray too damn easily... and the fancy handshake between the charger and the computer fucks up and it won't do anything. Whereas a simpler two-wire braindead charger will continue to work until the conductors completely split.

The dell system is admittedly interesting though. And crazily, it will actually work with some HP chargers. It says the wrong wattage power supply is connected and wont always charge, etc etc, but it will boot and run the machine. I was totally shocked(heh) the first time i tried that and it worked without a hitch.
posted by emptythought at 10:07 PM on September 2, 2014

Lenovo, FWIW, apparently use a simple resistance-based system.
posted by We had a deal, Kyle at 10:12 PM on September 2, 2014

Fucking Dell... Should have learned their lesson when they created proprietary power supplies for their desktop / towers which had connectors that look nearly identical to the ATX standard (and which often "fit" but had entirely different pin outs). They made it harder to support their machines if you weren't an "authorized" tech, though the quality of this name brand sub-contracted work was slow and not reliable, and the contracts were not at all a good deal for the tech nor the customer. I do understand the need for some proprietary tech in rapid battery chargers, but especially for laptops and mobile devices, the chip shouldn't live in the adaptor, and a laptop should take a standard charger, unless you're the kind of company that considers consumer backlash intrinsic to the product life cycle.
posted by krinklyfig at 10:16 PM on September 2, 2014 [1 favorite]

I do IT in a school district that contracts (nearly) exclusively with Dell

Yes, that's the ideal scenario supporting Dell. Otherwise, and especially without service contracts on old machines in small business environments, it gets challenging.
posted by krinklyfig at 10:21 PM on September 2, 2014

METAFILTER: 403 FORBIDDEN BOLLOCKS
posted by Sebmojo at 11:45 PM on September 2, 2014 [4 favorites]

I don't understand why Dell does this. It is unnecessary complication. I can't see that this has any useful function except as a sort of DRM, requiring you to use only Dell replacement parts.

Do we have a term for when you ask a question and then provide the obvious answer? If we don't have one we should.
posted by Dr Dracator at 12:18 AM on September 3, 2014 [2 favorites]

Yes exactly, the reason is gouging, it's similar to all phones having different chargers, I remember hearing someone in a Nokia shop being charged €60 for a replacement charger once.
posted by GallonOfAlan at 12:32 AM on September 3, 2014

Except most phones don't have different chargers anymore, unless you're Apple that is.
posted by jamincan at 2:04 AM on September 3, 2014

Giving people the ability to lie about what the charger can actually provide simply leads to worse performance (e.g. CPU throttling, as CynicalKnight mentions) and reduced battery life (since the battery is likely to be repeatedly under/overcharged.

Pretty much all laptop batteries since the switch to lithium based cells have integrated charging circuitry. These accept a wide input voltage range and buck it down to charge and balance multiple banks of cells at a constant current/constant voltage cycle.

While exaggerating the available current would probably lead to issues, I expect the idea was to use a generic laptop charger and have the adapter tell the computer it's actually a Dell charger capable of delivering an equal or lesser current.
posted by delegeferenda at 2:10 AM on September 3, 2014

Except most phones don't have different chargers anymore, unless you're Apple that is.

The EU has been moving towards a standard phone charger at their customary lightning speed - I don't know how much this has influenced the de facto standardization to micro-USB so far.
posted by Dr Dracator at 2:41 AM on September 3, 2014 [1 favorite]

Pretty much all laptop batteries since the switch to lithium based cells have integrated charging circuitry. These accept a wide input voltage range and buck it down to charge and balance multiple banks of cells at a constant current/constant voltage cycle.

I've not seen a laptop battery with this arrangement - they normally just have a simple monitoring/protection circuit and all of the power electronics are on the motherboard. And it would be quite unusual for a charging circuit accept a wide range of input voltages when it's the job of the external PSU to provide a regulated fixed voltage.
posted by grahamparks at 3:07 AM on September 3, 2014

One laptop battery I recently tore apart had a TI bq20z45 chip inside, a programmable chip for 2 to 4 lithium batteries in series accepting an input voltage between 4.5 and 25 V. Another battery, from 10 year old LG, had a bq20z80 monitor chip and a bq29312A balance charger chip, accepting the same voltages. While I am no expert, I have never seen a laptop battery without at least under/overcharging and over current protection ICs.

In either case, due to the cc/cv charging needs of lithium cells, the input voltage from the laptop charger will always pass through at least one voltage regulator before charging the battery. Even a cheap single cell charging IC like the TP4056 will accept voltages around 4 to 8 V.
posted by delegeferenda at 5:29 AM on September 3, 2014

I have fried a motherboard by using the wrong power adapter. Not that others should be gouged because I was an idiot.
posted by Obscure Reference at 5:32 AM on September 3, 2014

The EU has been moving towards a standard phone charger at their customary lightning speed - I don't know how much this has influenced the de facto standardization to micro-USB so far.

Unfortunately, microUSB is a really badly designed connector. It is particularly bad as a phone connector, since it is easy to get pocket lint jammed in it which blocks the connection. But even Apple has been playing along, they provide a tiny Lightning to microUSB adapter in case you want to use your iPhone with any existing adapter. However, the Apple phone adapters are so superior in quality I don't know why you'd want to use some other cheap crap adapter. And the Lightning connector has some advantages, like it can be inserted either way (there is no wrong orientation) and the wedge design pushes dirt out of the way.

Except most phones don't have different chargers anymore, unless you're Apple that is.

The adapters are all the same. They all work the same. Only the USB cable is different, depending on whether you have an old or new connector on the phone. I have used my iPhone 1 charger with my iPhone 5, it works fine.

And even Apple's laptop adapters are universal. A 45W MacBook Air will still power a MacBook Pro that requires 60W, although it doesn't have enough power charge and power the unit under high demand at the same time. You can even get an adapter for old MagSafe 1 connectors to convert to MagSafe 2. So can we stop the mindless Apple bashing?
posted by charlie don't surf at 5:34 AM on September 3, 2014 [5 favorites]

Except most phones don't have different chargers anymore, unless you're Apple that is.


I pretty much decided to go with Android last time because I thought I have a bunch of micro-usb cables which I use for all sorts of other devices, and I even have some old ipods that use the big charger, I am not getting a new phone that uses an entirely new charging cable that I do not use for anything else which will either get lost or eaten by a cat.
posted by jeather at 5:43 AM on September 3, 2014

I have had a Micro-USB phone for damn near the entire 7 years that they've been on the market, and I've never ever gotten anything jammed in the connector. Compared to previous designs, it's fairly robust, in that all of the moving parts are in the (easily-replaceable) plug, rather than the jack. (Apple gets credit where they're due -- the dock connector also used this strategy)

Lightning might be superior, but Apple chose to ignore a widely-adopted standard, and used a plug design that effectively utilizes DRM to prevent 3rd-party vendors from manufacturing their own cables at low-cost.

And, yes. Apple's power bricks are generally very well-made. However, nothing about that justifies abandoning the nearly-ubiquitous USB connector design that everybody else uses.
posted by schmod at 5:45 AM on September 3, 2014

> I don't understand why Dell does this. It is unnecessary complication. I can't see that this has any useful function except as a sort of DRM, requiring you to use only Dell replacement parts.

That's weirdly paranoid and overthinking the matter. Dell is facilitating the ability to swap some parts safely while minimizing the risk.

If every charger type had a unique plug, that would be the big dumb stupid DRM-ish thing. Because then your IT department's spare parts box would have to have a unique power brick for every single model of laptop in the company. Instead, IT can keep a smaller inventory and spot you a 90 watt power brick for your netbook -- a pain in the ass to carry around, but not nearly as inconvenient as having no power at all -- until the proper replacement power brick comes in. Or, if you're shopping for yourself, you have a wider range of options and can shop around a little on Ebay.

Storytime: The metal-case Apple 20" and 23" Cinema Displays had a reputation for blacking out inexplicably with an SOS-ish error code. The official fix was to have Apple replace the inverter board ($500-ish). The just-as-good-and-cheaper fix was to replace the stock 65 watt external power supply with the 90 watt power supply from the 30" Cinema Display ($100-ish via Ebay). The hack-to-rule-them-all was to tape over the center pin on the connector of the cable between the stock 65W power brick and the monitor (<$0.01 for a sliver of tape), which effectively cut short the power-on handshake. Since the brick was already designed to power the given monitor, this wasn't as harmful as it sounds (although cutting a ground line isn't harm-free, even if it's within a closed, protected circuit). I was able to restore a couple-three monitors in the office I worked at this way.
posted by ardgedee at 5:46 AM on September 3, 2014 [3 favorites]

delegeferenda: Pretty much all laptop batteries since the switch to lithium based cells have integrated charging circuitry. These accept a wide input voltage range and buck it down to charge and balance multiple banks of cells at a constant current/constant voltage cycle.

Yeah, I oversimplified in my original comment (you really didn't want to read my original half-rant about arduweenies and their misleading misunderstood misexplanations of basic electronics, and this ain't the place for extended technical discussion), but grahamparks has pretty much got it right. And regardless of that, the charge controller still needs to know what the power supply is capable of...

One laptop battery I recently tore apart had a TI bq20z45 chip inside, a programmable chip for 2 to 4 lithium batteries in series accepting an input voltage between 4.5 and 25 V. Another battery, from 10 year old LG, had a bq20z80 monitor chip and a bq29312A balance charger chip, accepting the same voltages.

Perfect examples - the bq20z45's a charge monitor (aka "fuel gauge") and protection/monitoring front-end; basically a bq20z80 + bq29312A in a single chip. Both still need to talk to a charge controller, which itself still needs to know the capability of the power supply so it can decide whether it can charge at (for example) 1.2hrs @ C1, or whether it needs to drop down to something lower that the power supply can handle. And, in either case, what the expected endpoint parameters (temperature, impedance, overcharging indications, etc) will be.
posted by Pinback at 6:02 AM on September 3, 2014 [1 favorite]

For those that are unfamiliar with standards: XKCD. Having the ability to swap out components with a given brand with complete interchangeability means the product lasts longer. A few years ago, a friend of mine with a four year old computer went to replace his Mac's power supply because the connector was wearing at the strain relief. He called his apple store and they told him he needed an appointment. He made an appointment at the genius bar about a week out, brought his computer in, and they told him 'nope, we don't sell that connector any more.' Four minutes later he ordered it on ebay because otherwise he had a four year old brick. Interchangeability means you can continually upgrade either the power supply or the computer and be able to support your products long after the competition tells you 'sorry, you are out of luck.'
posted by Nanukthedog at 6:09 AM on September 3, 2014 [3 favorites]

Pinback, you seem way more knowledgable about this than I am. I know a bunch about batteries but not so much about laptop power circuitry. Obviously I was incorrect about where the voltage regulation for the battery charging takes place. Apologising in advance for conjecture and guesswork below.

I still don't see how a bad AC adapter would damage the batteries. From my understanding most laptops don't rely on the input voltage being that cleanly regulated, is this incorrect? Most adapters look like cheap switching mode supplies.

If the computer is drawing more power than the adapter is rated for, I'd expect voltage to drop. A "dumb" laptop, which has no knowledge of the adapter's capabilities (or possibly has been misled by our hypothetical adapter), will begin drawing higher current to compensate the voltage drop. The failure modes that I see happening here are either that the laptop power reg circuitry hits the dropout point where it can no longer deliver the desired internal voltages, or else that the over current makes the AC adapter fail.

In the first case, I'd expect the computer to have a fail safe causing it to shutdown. In the second case, the AC adapter can fail more or less gracefully. Something as simple as a resettable PTC fuse would allow it to fail without permanently bricking itself (pun acknowledged). Worst case scenario, where there isn't any kind of fuse (hopefully this AC adapter would not be legal to sell), it will overheat, possibly starting a fire or outputting mains voltage into your laptop. In the last scenario your batteries might well be affected, but I don't think that's very on topic.

While I see why it would be very useful for a laptop to know what kind of input power is available, apart from the catastrophic failure I don't think the batteries are at risk. And even if the AC adapter is authenticated, I'd hope that my laptop monitors that the input voltage is within spec. Even an authentic adapter can fail, from deteriorated capacitors, bad solder jobs or whatever.

While not a fan of DRM type technology, recurring stories about mobile phones and electronic cigarettes exploding makes me think that there can be good reasons for not making power adapters interchangeable.

As an aside, the Lightning connector has huge issues with corrosion. Especially if exposed to toddler saliva. And I can't wait for the new reversible USB 3.1 type C connector taking over.
posted by delegeferenda at 8:13 AM on September 3, 2014 [1 favorite]

Apple will have the same charger connector as everyone else in the EU, since a recent ruling.
posted by GallonOfAlan at 8:57 AM on September 3, 2014

... For bonus points you could make it programmable, to report anything you wanted/needed.

Yeah, my first thought was 'That's an interesting attack vector; not quite as sexy as cracking personal keys via cpu acoustics, but honestly, how often do you look carefully at your power supply?'

But that was my first thought because I use my powers for eeeeevil.
posted by eclectist at 9:02 AM on September 3, 2014 [1 favorite]

Yeah, fuck you Dell for this. I've got a nice, but older so not worth out of warranty repair, Dell laptop that's stuck at half processor speed because somewhere on the motherboard the signal that says "I'm a 90W PS" get's lost and it thinks it's connected to a lower wattage supply (yes, I've tried multiple supplies).
posted by kjs3 at 9:20 AM on September 3, 2014 [1 favorite]

> However, nothing about that justifies abandoning the nearly-ubiquitous USB connector design that everybody else uses.

>Being able to plug the iPhone in when it's dark and not having to fumble with the connector being the "right" way covers a lot of proprietary sin.

The USB organization just released the final specs for the new type-C connector which is reversible. I would expect to start seeing the new connector on phones and tablets by the end of the year.

Unlike the proprietary Apple Lightning connector, the new USB connector will be a universal product standard.
posted by JackFlash at 10:28 AM on September 3, 2014

That Type-C USB connector still looks fragile; hope the metal they use for the housing is reasonably robust and that it doesn't lint-load too quick.
posted by caphector at 10:46 AM on September 3, 2014

I've telling my boss about this for years, trying to convince him to stop buying off-brand pa-10/pa-12 style adapters. I'ma send him this article.
posted by The Great Big Mulp at 11:47 AM on September 3, 2014

Of course, knowing him, he's probably just going to try to convince me to hack them per the instructions.
posted by The Great Big Mulp at 11:51 AM on September 3, 2014

my first thought was 'That's an interesting attack vector [...] how often do you look carefully at your power supply?'

If you stop posting I shall presume you got a job with the NSA.

The existing protocol seems to be safe from an attack like this, as it apparently only reads a certain number of bytes and rejects ones that aren't on a whitelist. But Dell's BIOSes are reprogrammable, and it wouldn't be at all hard to make one that would behave in unspecified ways when finding a particular voltage code, or simply any code it can't recognise. For all we know they already do this: bugs that occur due to dropping out of if-then-else statements can be very hard to recognise. And the protocol is two-way: the BIOS can use the power supply as a transmitter.
posted by Joe in Australia at 3:36 PM on September 3, 2014

Lightning might be superior, but Apple chose to ignore a widely-adopted standard, and used a plug design that effectively utilizes DRM to prevent 3rd-party vendors from manufacturing their own cables at low-cost.

Yea, really, preach.

I only own apple stuff. I don't own a single computer that isn't a mac. I had an ipad, and me and my partner both have iphones.

And wow, I completely hate this shit. Because even two years in, it's still hard to find a proper spare cord for your phone when you're out and about, whereas it used to be even easier(and kinda still is) to find a 30pin cable than a microusb. And i swear the lightning cords fall into a failure mode even easier than the old cables, wherein if they get damaged at all they just refuse to charge or do... anything. 30pin cables could often be wiggled into submission and semi-functionality and at least charge your device, but lightning cables are finnicky and require that handshake.

What i could have accepted would have been some kind of handshake for any functionality besides charging. But the standard should have been "these pins are always charging unless handshake" and just let the chinese cloners go wild.

I also LOL at any supposed superiority on the lint/dust front. Me, and several of my friends and coworkers have had to either carefully clean the sockets by hand, or go to the apple store and have them clean them for free when the cables stopped seating properly. I would have written this off as "well, i work in a high dust environment" if it hadn't happened to such a disparate group of people device usage conditions wise.

It's sad too, i feel like lightning as a connector is mechanically superior to anything else out there. But the stupid chip lock-in even for charging just sinks it. I also swear apple cables are getting shittier each generation. Up until the 4S i was using(and still use with my ipad 3) the cable from my 3rd gen ipod that must be 11 years old now. I literally got that cable in middle school, and i'm 24. It survived high school, college, and unimaginable debauchery. The cables that came with my iphone 3g, 4, and 4s fell apart instantly. As did my ipod nano 2g cable. The cable that came with my iphone 5 fell apart so fast that they actually gave me a free one under warranty. And it seriously stayed in my bedroom, plugged into the charger and never moving essentially 24/7.

And of course any actually reliable and officially licensed cable like the ever thick as hell belkins cost like.. $13. Whereas you can get a sturdy microusb for $2.

So i'll hate on apple all i want, thank you very much. MFI is completely stupid. Total face welded to palm shit. It didn't stop sweatshop cables from being made, it just ruined the customer experience.

Also, it's easy to make fun of microusb as a standard as well once you move into the newer high speed connectors that still are forced to deal with backwards compatibility. look at this stupid fucking connector. The new reversible standard looks promising, but then, hey, we have another dumb cable.
posted by emptythought at 3:59 AM on September 4, 2014 [1 favorite]