KS-18L charger plug polarity

[Seba]

Hi,

what is the polarity of KS-18L charger plug? Outside contacts are positive or negative? I don't have charger with me, so I can't verify with multimeter.

[Seba]

Ok, back home and checked - center pin is not connected, internal contact is negative, external is positive. This is contrary to what may be considered a standard, that exposed contact is negative. This is also why Inmotion charger won't work, despite of matching voltage and connector. 

[Siggy]

@Seba such awesome info in this post and the other about rapid charging.

 

I was fascinated and really wanted to try this out, so bought the following:

1) Lenovo cable

https://www.aliexpress.com/item/DC-Tip-Plug-Connector-Cord-laptop-power-Cable-For-Lenovo-IdeaPad-Yoga-Square-Connector-Charger-Laptop/32829618382.html?spm=a2g0s.9042311.0.0.70ca4c4d3jrRiS

 

2) 84v 4a charger (with crocodile clips)

https://www.aliexpress.com/item/84V-4A-Li-ion-Battery-Charger-For-72V-4A-lithium-Battery-Electric-bicycle-Power-Electric-Tool/32842291815.html?spm=a2g0s.9042311.0.0.70ca4c4d3jrRiS

 

I have a question:

What is the correct way to connect the charger croc clips and lenovo cable (i.e red to white (+/-)

[Seba]

1 minute ago, Siggy said:

What is the correct way to connect the charger croc clips and lenovo cable (i.e red to white (+/-)

Rule No. 1 - Don't trust the colors  It's best to use multimeter set in DC voltmeter mode - turn charger on and confirm if  red clip is really "+". You will also verify, if output voltage is correct - ideally it should be 84.0 V or at least between 83.5 - 84.5 V. Next, switch multimeter to continuity test and check which wire is connected to the outer contact of Lenovo plug. This is also "+" for KS-18L/XL.

[Siggy]

hehe roger that!! Thanks @Seba

So (+) will be 83.5-84.5v on charger... what should the (-) reading be?

 

Also, what do you mean by Outer contact

is that the white and back cables pictured in 1)

[Seba]

13 minutes ago, Siggy said:

So (+) will be 83.5-84.5v on charger... what should the (-) reading be?

You connect multimeter between red and black clip. Black alligator clip should go to multimeter COM port, red one to port marked with V letter (there may me more letters or symbols, but V should be one of them). If you are reading voltage without minus sign, everything is OK - it means that polarity is correct. If your readout is negative, it means that polarity is reversed, so the clip that goes to multimeter COM port is in fact "+".

Next, disconnect clips, switch multimeter to continuity test (or ohmmeter). Short two multimeter probes - you should hear beep and/or see zero resistance on display. Now determine which wire (white or black) gives the same result - connect one probe to white wire and second probe to the outer (external), visible metallic contact of Lenovo plug. If you hear beep and/or see zeroes on the display, this means that this white wire is "+". If there is no beep or display doesn't show zeroes, try with black wire. If neither wire works, you're probably doing something wrong or the cable is damaged.

[Siggy]

Fantastic @Seba thanks for spelling that out for me. 

 

I am a complete beginner at polarities and voltmeters. 

 

Now I'm even more excited for the parts delivery to test this out. Will report back