Which models is W520's 170W AC adapter compatible with if keying removed?

[neilthinkpads]

Since the T60, I've had the 90W AC adapters around my home.

Now that my stable of daily ThinkPads includes W520, I'd like to replace all the 90W with W520's 170W.

If I remove the plastic keying on the 170W AC, can I also use it safely with T520, X220, and X200?

(I assume that Lenovo used the keying to protect *some* ThinkPad models for which it wasn't safe, but I don't know which ones.)

[TPFanatic]

It'll work with all of them no problems. X200 and older may ID it as a 120W, but since that's underreporting I don't see a problem.

[neilthinkpads]

Thank you. Anyone happen to know with which models the W520 170W with keying removed *isn't* safe?

[dr_st]

I wouldn't use it with any laptop that mentions >170W as requirement. However, even for those, I think actual safety concerns would be very very negligible.

[kfzhu1229]

I wouldn't use it with any laptop that mentions >170W as requirement. However, even for those, I think actual safety concerns would be very very negligible.

As for safety concerns, from my experience, business class laptops would be careful with this stuff and would most probably throttle itself (or not charge battery) when you use an underpowered charger. And if that end doesn't throttle, the charger would have its protection from going beyond its capabilities as mentioned below. (and AFAIK this protection is much stronger and smarter than overcurrent protection on a desktop PSU) Not quite an afterthought protection but charger will age more poorly.
Home laptops on the other hand are kinda a different animal when it comes to this. I learnt the hard way for example HP shipped underpowered 65W chargers on basically every Pavilion dv6000's - even one with efficient Penryn CPU and GMA X3100 would hard throttle the CPU when you charge the battery, and one with dGPU would easily draw over 90W on the meter when I tested it with a 90W charger (yet only 17" dv9000's shipped with 90W)! My guess is that for these laptops they don't care much about reliability and wants to cheap out on chargers and also gives you a "lighter weight".
The end result is that the 65W chargers age very poorly on those laptops - not because the charger itself is low quality - same charger ages very well on a HP Compaq nc6220/nc6230 - but because it's been pushed to its limits basically whenever it's connected!
Their Compaq business class laptops on the other hand is very cautious, just like the T6x ThinkPads.
So the takeaway is I believe these chargers will run at their max capacity just fine if you push it that hard - just they will age much more poorly - I have seen 3 Pavilion dv6000 chargers with brittle wires and stuff (but the ones shipped with nc6220 are fine despite same model) and my 90W dv9000 chargers are all in like new condition.