Universal laptop charger 90W - 15~20V How to of specific voltage selection !!

[Kiriakos GR]

I have never touch before any Universal laptop charger.
They claim automatic voltage selection from 15~20V DC, and they come with a pack of several laptop plugs.

My find of Universal laptop charger at 90W, this circulated at the Greek market, somewhere at 2014 and later.
The product this were marketed as Powertech but such brand does not exist, and with a bit of further research I came across the name of XPOWER, and with a dive to higher depths I did discover xpower.hk the real father of this product. 

Active protection: Short circuit/ Over-power/ Over-voltage/ Over-current

DCV end of cable comes with three wires, and this is somewhat confusing.
The first though this is that third wire this should be serving as separate voltage monitor for micro corrections under load.
The reliability this is much different, whom will though that those power connector bits they include a hidden resistor?

Its one power connector bit according to on-board resistance value this will inform the charger of what voltage output to deliver !
 

POWERTECH - M5 - 5.5x2.5mm HP-IBM-DELTA-ASUS.

Acer:  19V/3.42A,19V/4.74A
ASUS:  19V/4.74A
Dell:   19V/2.64A,19V/3.16A,19V/3.42A,19V/4.74A
Gateway:  19V/2.64A,19V/3.16A,19V/3.42A,19V/4.74A
Hasee:   19V/3.42A,19V/4.74A
IBM:  19V/3.16A,19V/4.2A
NEC:   19V/4.74A
Toshiba:  19V/3.42A,19V/3.95A,19V/4.74A 
Lenovo:  19V/4.74A
Liteon:   19V/3.16A,19V/3.42A,19V/3.95A,19V/4.74A etc.

Right now after my NEW finding, I can freely speculate that all similar three wires Universal laptop chargers,  they use identical trickery 

From the side of an electronics repair man, this situation it is a huge puzzle in case of DC cable and plug replacement.
For a proper job, the charger it should be modified internally so the appropriate sense resistor  to be installed, and then you may use a regular two wires new cable with an compatible plug regarding dimensions.

(Inquiring minds might think to add a resistor pot instead, but this is a bad idea in this case.)
Do not do it.