No, you can't replace a 20 V, 6 A, 120 W unit with a 19 V, 3.42 A, 65 W unit and expect it to work properly. At best, the smaller adapter might be able to slowly charge your battery but it won't be able to actually power your computer as an AC adapter. At worse, it will run too hot trying to provide the power the system wants to draw, melt down, and catch on fire.

 

I use this Kensington 33197 Universal Charger, I've had it for years and several laptops. It's slim and light and comes with a whole host of charging connectors.

FWIW, using 19V instead of 20V will not hurt the laptop, but as stated, you might overload the smaller charger due to it's current limitations.

 

You typically want the voltage rating to be the same. I doubt 19 vs 20 would be a problem. In fact, since many laptop batteries are 19VDC. and since "all" chargers need to output slightly higher voltages than the batteries they are designed to work with, I suspect that 20V is normal - just more honest/accurate labeling.

Hmmm, out of curiosity, I just measured the output of my "19V" (according to the label) charger for my MSI laptop. It read 19.98VDC.

Note this higher voltage requirement is seen most commonly in our vehicles. Alternators typically output 13.5 to 14.8VDC yet we all know our car batteries are 12V. If the Alternator output 12V, our car batteries would never fully charge. Same with all batteries and chargers. The charge output is always a little higher.

So in your case, a slightly lower output voltage would result in a laptop battery that never fully charges - at least while you were on the road.

The big and most important issue is the current capability of the charger. It is critical to understand that laptop chargers are also laptop power supplies. That means they MUST have enough current capability to charge the battery and, at the same time, run the laptop. Your original charger has a 6A capability. The ASUS only 3.42A. That is not good. If lucky, that laptop will just refuse to run while charging. Worse case is the charger will overheat, catch fire and burn your hotel down while you sleep.

Note power(W) = current(A) x voltage(V). Hence 19 x 3.42 =64.98W while 20 x 6 = 120W.

I would advise against that ASUS. If you decide to get it anyway against that advice, only do one, or the other. That is, if you want to use the laptop, remove the battery first. If you want to charge the battery, keep the laptop powered off. NO EXCEPTIONS. That said, if the laptop requires more than 65W on its own, be ready for instability, sudden system crashes, and possible loss of all your important data due to drive corruption!

 

Thank you for your replies ! So would this one work instead ?

 

No, that's a USB charger for a phone. Your laptop requires an AC adapter with the proper output plug type. You can't power your laptop by pluggin a charger into one of its USB ports.

This is the AC Adapter your unit needs based on the model you posted. However, I don't know why you want another one as you have one according to your picture. Unless the one you have is no longer working. There is a reason why your AC adapter is as big as it is and it's called physics. You are not going to find a tiny, lightweight replacement that produces 6 Amps at 20 Volts.

Amazon.fr

ASUS 120W DC Adapter - Tech Specs｜Adapters and Chargers｜ASUS Global

ASUS 120W DC Adapter keeps you going and charged wherever and whenever needed.

www.asus.com

 

There is a reason why your AC adapter is as big as it is and it's called physics. You are not going to find a tiny, lightweight replacement that produces 6 Amps at 20 Volts.

I'll have to disagree, I posted a more compact and lightweight model, the Kensington 33197 Universal Charger.

 

Just as a point of information.

To charge a battery, which is DC you need to apply a DC voltage of at least the battery voltage across the terminals.

Since most chargers are fed from the mains (or on a Car from the alternator) which is AC, the supply has to be rectified, and rectification is usually performed by a bridge rectifier, which is composed of 4 diodes, two passing current on the positive part of the AC cycle, two on the negative.

Since voltage drop across a diode is typically 0.7V, then drop across 2 is 1.4V, which is why the voltage to a car battery is typically measured at 13.4 V.

 

To charge a battery, which is DC you need to apply a DC voltage of at least the battery voltage across the terminals.

Well, it's a whole lot more complicated than that for the typical laptop lithium battery pack! The charging circuit is monitoring cell temperature and individual cell voltages. Gone are the days of lead/acid batteries where you just applied a current limited voltage.

 

If you just want a charger capable of charging your laptop's battery overnight then several units will suffice. However, if you want an actual AC adapter that is capable of running your laptop on AC power consistently then you will find that those cheap, lightweight units are not going to cut it. That Kensington universal charger came out in 2008 and is not being produced any more. None of the major electronics retailers carry it. Reviewers mention that it ran way too hot when doing anything but slow charging.

 

I don't know what reviewer were doing to it, I've had mine for years and it never got that hot, certainly not excessively so. It powered a 17" HP laptop with two hard drives with no problem at all.

 

Yeah, I hate when they say something like "way too hot". That does not mean jack to me. Does it "smell" hot? Is the plastic melting and becoming deformed? Is holding against my skin intolerable? If any of those are "yes", then it may be too hot. Otherwise, it might just be "very warm" which might be normal - especially if charging a discharged battery and operating the computer at the same time.