W520 w/ Mini Dock Plus Series 3 wattage error

[NoPyro]

Hi, first post here so hoping this is the right place to ask:

Earlier this year I bought a used w520, brilliant device and perfect for my nerdy self to tinker with, but I'm having an error with the dock, half the time or more, when I dock the Thinkpad and power it on it will complain about the attached AC adaptor having the wrong wattage, then ask me to confirm boot, if I do all seems well, and if I turn it off and re-seat it after a few attempts it stops complaining, all continues to be well. The adaptor is a 170W 20V 45n0111/2 and seems genuine, as said it can power everything fine but the warning is rather annoying, any idea what is causing this? Could the adaptor be fake or do I just need to do a better job of cleaning the docking port? Is it maybe a BIOS issue? I'm totally lost and this isn't the first place I've asked, but it just wont go away.

Any and all help would be greatly appreciated and I can provide any info needed to diagnose this if asked.

[RealBlackStuff]

Welcome to the Forum.
When you dock, do you connect the charger to laptop or dock?
Also, there are 3 dock-versions: https://support.lenovo.com/ie/en/solutions/pd024298 although AFAIK all 3 should be able to handle 170W.
The Lenovo charger weighs ~770 g (1.70 lb), if yours is lighter, you have a Chinese knock-off.

[NoPyro]

When you dock, do you connect the charger to laptop or dock?
Also, there are 3 dock-versions: https://support.lenovo.com/ie/en/solutions/pd024298 although AFAIK all 3 should be able to handle 170W.
The Lenovo charger weighs ~770 g (1.70 lb), if yours is lighter, you have a Chinese knock-off.

I connect to the dock, every time.
My dock is a 4338, Mini Dock Plus Series 3 w/ USB.
My charger is 674g, it is a UK charger if that affects it.

I feel it's worth mentioning that with a re-seat or two it DOES work, and it has the properly notched connector, if that changes anything, but with the weight I'm starting to question.

[dr_st]

Perhaps try using this charger directly with the laptop without the dock? To see if the same intermittent error comes up.

[NoPyro]

Perhaps try using this charger directly with the laptop without the dock? To see if the same intermittent error comes up.

Ah I forgot to mention, in my experience it hasn't done this, I HAVE tested it a bit before, but I will do so more now and update you when I have, try and see if it occurs w/out the dock.

EDIT: Testing shows no errors, the laptop likes the charger just fine, I guess it's either an issue with the docking port or it's a faulty/fake charger that can handle just the laptop but not the laptop AND dock?

[dr_st]

I don't think it's a problem with the charger. The laptop detects the charger wattage via a handshake that measures the resistance across the sense wire (center pin) of the charger's barrel plug. If the connection somewhere along the path of dock power socket --> docking port on dock --> docking port on laptop --> laptop power circuitry is faulty, you may get symptoms like this, but when plugged directly into the laptop it would behave fine.

If cleaning connectors doesn't help, and if the problem becomes too frequent/annoying, the easiest thing would be to try to get a different dock. They should be readily available these days.

[NoPyro]

I'll probably keep using it, testing, trying to clean it if it crops up again then, if it keeps being a problem I may as well try a new dock, thank you for the help!

I do have more questions regarding my Thinkpad, would it be okay to ask here or is it smarter to open a new topic? Hopefully it's okay to ask that at least.

[dr_st]

If it's not related to this problem, it is better to open a new topic.