Thinkpads Forum

I have a 45W travel charger that's both much lighter and smaller than the monster brick that Lenovo supply you with, and it's an all-in-one form factor with multiple exchangeable plugs (US, Europe, Australia, Asia) that go directly into the charger, so you don't need to carry around a pile of cables and/or travel adapters. According to this blog post it's possible to use the Helix 45W adapter with an X1, however the text also implies that the laptop recognises the adapter ("ThinkPad X1 Carbon recognises the 45 watts adapter"). Is this some Lenovo-specific magic like Apple's USB power circuitry, or is it just taking the current draw and extrapolating? The more direct question is, is it possible to use a non-Lenovo 45W travel charger with an X1, or do you need to get the Helix one (which negates most of the benefit of the travel charger I have)?

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I believe that the "magic" has to do with a signal pin that is part of the Lenovo AC adapters. The usual 20V round barrel plugs have a center pin which is connected to a resistor. The value of that resistor is read by the laptop's power circuitry and this is how it "knows" what's connected. I'm assuming that the slim tip (USB-looking) power plugs have a similar setup.

If the manufacturer of the non-Lenovo adapter has done their homework properly, they also will have duplicated the resistor identification system. If not, then your laptop may default to whatever "no resistor detected" means to it. With the 20V round barrels, no resistor = 90W adapter being used. Not sure what it would be for the slim tips.

edit: Found this at thinkwiki: http://www.thinkwiki.org/wiki/Power_Connector#slim_tip Seems like "no resistor" may not be supported by the Lenovo hardware.

Ouch! Thanks for that pointer, so they're using an Apple-style trick. Looking at this eBay photo I'm guessing that you've got the DC power on the connector's outer and inner sleeve and then the supply-type signal on the centre pin. Given that the eBay adapters have a straight 2.1mm socket on the back, unless they have an internal resistor they're not going to work (the official Lenovo adapter appears, from the photo, to have a round-barrel version of the square-barrel connector on the input site as you've mentioned, so presumably it doesn't have this problem). This seller has one listed for $1.05 including shipping, I'm tempted to get one to see what it reports itself as.

Alternatively, if anyone has one of the non-Lenovo 2.1 -> slim adapters and can measure the resistance, it'd be useful to know what they are (or at least what a sample of them are, who knows what else may be out there). Since Lenovo have overloaded a power supply connector with extra functionality, you could potentially end up with some nasty surprises if you use an adapter that doesn't report the correct power source.

Why not just use the lenovo 65W travel adapter the plugs directly into the wall and has adapters for all countries? It will allow you to have rapidcharge that the 45W adapter won't.

Lenovo 65W Travel AC Adapter - US - Part number: 4X20H15594
http://shop.lenovo.com/SEUILibrary/cont ... 4X20H15594

It's only 0.44 pounds
more info - product sheet
http://download.lenovo.com/ibmdl/pub/pc ... h15594.pdf

http://gw.alicdn.com/bao/uploaded/i1/TB ... em_pic.jpg

bigcatny wrote:Why not just use the lenovo 65W travel adapter the plugs directly into the wall and has adapters for all countries?

A number of reasons, the primary one being that I didn't know it existed until you told me about it . Secondary reasons are that it appears to be pretty hard to find outside the US, and in particular isn't available where I am, and that from what I've been able to find out from Lenovo sites, although it can handle plugs for other countries, it only ships with the one for the country where it's sold, and that seems to be just the US.

However, Googling around with keywords from the Lenovo adapter leads to other equivalents, a KFD one, e.g:

http://www.ebay.com/itm/65W-AC-Adapter- ... 1837379994
http://www.aliexpress.com/item/65W-20V- ... 34266.html

but I'm still waiting to hear back whether they'll ship with multiple plugs or only the US one. There's also this no-name one:

http://www.aliexpress.com/item/For-Leno ... 20611.html
http://www.aliexpress.com/item/2015-the ... 03066.html

which is depicted with multiple plugs but that doesn't mean it'll ship with them (a problem I've run into in the past). There's another style of KFD:

http://www.ebay.com/itm/KFD-65W-AC-Adap ... 1711568157

and finally the one I already have but with the Lenovo slim connector:

http://www.amazon.de/Ultrabook-Netzteil ... B00NBKREP0

Now this one is at least useful because I have the plugs for it for different countries, and you can source them from Aliexpress with the right Googling.

So, it appears you can get this, if the vendors will ship with multiple plugs (none of them have replied yet), or if you get the last one and source the plugs independently.

blueline wrote:Alternatively, if anyone has one of the non-Lenovo 2.1 -> slim adapters and can measure the resistance, it'd be useful to know what they are (or at least what a sample of them are, who knows what else may be out there). Since Lenovo have overloaded a power supply connector with extra functionality, you could potentially end up with some nasty surprises if you use an adapter that doesn't report the correct power source.

Answering my own question, two different connectors from different vendors both have a 550 ohm resistance to the centre pin, which means they identify as 90W chargers, which seems to be the default for X1 chargers. I'd expect others to be the same... they're sealed units so even if I destroy one to find out how they're wired, that doesn't help in modifying others to work as different power-level connectors.

In any case it looks like it won't be a good idea to use these adapters with any charger rated at less than 90W (for > 90W you just end up underutilising the full capacity), since you'd constantly be triggering the overload protection when the X1 tries to draw an inappropriate amount of power from it.

blueline wrote:So, it appears you can get this, if the vendors will ship with multiple plugs (none of them have replied yet), or if you get the last one and source the plugs independently.

Updating this, this vendor sells KFD (= Shenzhen KFD Technology, a large power supply vendor) power adapters and will ship with plugs for multiple countries if you ask them. So that gets you a nice, compact, cool-running travel charger in a well-designed form factor that doesn't crowd out other devices plugged into the same power strip (I have an existing one for my Toshiba, which was why I was keen to get this particular one) with interchangeable plugs for US, UK, EU, and AU. Woohoo!

Any ideas if the power adapter from the Yoga 3 Pro 14 (Lenovo 40w slim travel adapter Part# GX20H34904) will work with the X1C first gen? I know the end connector is USB powered and has a slight contour edge for the Yoga Machines. Maybe if I remove the end and splice the cables from a current X1C end. Would be totally awesome and the adapter can be used to charge other USB cable charged devices.

My motherboard does not detect the battery as charging. So I just use the cord to power on the device and use.

Joeminati wrote:Any ideas if the power adapter from the Yoga 3 Pro 14 (Lenovo 40w slim travel adapter Part# GX20H34904) will work with the X1C first gen?

No, they use a totally different connector, and in particular the Yoga 3 uses a modified USB-style connector that looks superficially like a USB connector (and can function as a USB power source) but isn't proper USB, which is a good thing because most devices expecting 5V at 500mA would be quite surprised to be fed 20V at 2A.

(I suspect this was dreamed up by the same geniuses who did the X1 Gen 2 keyboard: "Let's take a connector that the entire world, and even Apple, uses to move 5V power, and modify it so it'll feed 20V as well").