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Would 1V too much from a car PSU damage a notebook?

post #1 of 19
11/30/09 at 8:56am
Thread Starter 
I am going to buy an Asus K50C-SX023V for my father. He used to have a Dell notebook a few years back, and he has the car PSU for that computer still around. Of course I'd have to solder on a new plug, but that's not a problem at all. I know my way around soldering irons. This is a good, reliable PSU, but it's rated at 20V, while the Asus is rated at 19V. Since this is only around 5 % increase in voltage my guess is that it's not a problem at all, and that it's well within the normal tolerance levels. Am I right?

The watts/amps are compatible, btw.
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post #2 of 19
11/30/09 at 9:33am
1V (+) for me is too much for a notebook, when taking in consideration that W/A is the same (even that). Just my opinion.

cheers ...
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post #3 of 19
12/1/09 at 9:42pm
Quote:
Originally Posted by Mastiff View Post
...it's rated at 20V, while the Asus is rated at 19V. Since this is only around 5 % increase in voltage my guess is that it's not a problem at all, and that it's well within the normal tolerance levels. Am I right?

The watts/amps are compatible, btw.
If I were you, I wouldn't do it. 1V is enough to damage your laptop unless it was designed to ressist that extra volt, wich I really doubt.

Remember this basic principle when replacing PSUs:

Voltage (V, Volts): Should always be the same, not higher or lower
Current (A, Amp, Amperes): Should be the same or higher, not lower

Cheers!
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post #4 of 19
12/1/09 at 10:47pm
I have no special education but I think you will be fine. But I must say if w and a are the same then v must be also? v=w/a? Or no am I being obtuse? There was a question regarding a Gateway a while back. The replacement adapter was several volts higher than original. Turns out stock was minimal, upgrade was recommended and all that was sold at several sites?

Anyone ever notice AC power brick and battery not the same voltage? I am pretty sure they all condition (do not know the correct term) the input current.

Mastiff while I think you will be fine. I must ask is an adapter not included? Also is $50 too much to spend vs a ghetto rig of the DeLL adapter?

Just thoughts and if my math is off let me know I sometimes make incorrect use of formulas.
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post #5 of 19
12/2/09 at 1:09am
That's why I said... unless it was designed to resist, and with that I meant that the input voltage needed was flexible.

The current, it should be the same or higher because the device (laptop in this case) has a certain current requirement and the PSU will supply that certain ammount as long as it doesn't reach the higher limit.

But the voltage is different, theorically the PSU will always supply the same voltage no matter if the device needs more or less voltage than the one the PSU can supply. And this will kill all those devices that were not designed to support this.

If you provide a PSU with a lower current than the one your device needs, the PSU will try to provide it, but since it can't actually fulfill the required amount of current, the voltage of the PSU will drop, this can damage your PSU and your device.

So, let's say your laptop needs 19.5V and 4.62A...

*A PSU with 19.5V and 4.62A is OK
*A PSU with 19.5V and more than 4.62A is OK (you could say that your PSU will be less stressed since it has room to give more power than the one needed)
*A PSU wuth 19.5V and less than 4.62A is NOT OK, if your laptop needs the full 4.62A, it will try to get them from the PSU and the PSU will respond dropping the voltage, so at the end you will get less voltage and less current that the one you need
*A PSU with less or more than 19.5V is NOT OK, no matter if the current is the same or higher than what you need. The PSU voltage will always (theorically) be the same, so your laptop will suffer froom the difference.

Once again, this is standard theory, there could be PSUs or laptops that have some special circuitry that regulate this differences in order to let the laptop work fine.

I have to admint that I have always wondered how universal PSUs work. Anyone knows?

Cheers!
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post #6 of 19
12/2/09 at 3:25am
Quote:
Originally Posted by Ericko View Post
That's why I said... unless it was designed to resist, and with that I meant that the input voltage needed was flexible.

The current, it should be the same or higher because the device (laptop in this case) has a certain current requirement and the PSU will supply that certain ammount as long as it doesn't reach the higher limit.

But the voltage is different, theorically the PSU will always supply the same voltage no matter if the device needs more or less voltage than the one the PSU can supply. And this will kill all those devices that were not designed to support this.

If you provide a PSU with a lower current than the one your device needs, the PSU will try to provide it, but since it can't actually fulfill the required amount of current, the voltage of the PSU will drop, this can damage your PSU and your device.

So, let's say your laptop needs 19.5V and 4.62A...

*A PSU with 19.5V and 4.62A is OK
*A PSU with 19.5V and more than 4.62A is OK (you could say that your PSU will be less stressed since it has room to give more power than the one needed)
*A PSU wuth 19.5V and less than 4.62A is NOT OK, if your laptop needs the full 4.62A, it will try to get them from the PSU and the PSU will respond dropping the voltage, so at the end you will get less voltage and less current that the one you need
*A PSU with less or more than 19.5V is NOT OK, no matter if the current is the same or higher than what you need. The PSU voltage will always (theorically) be the same, so your laptop will suffer froom the difference.

Once again, this is standard theory, there could be PSUs or laptops that have some special circuitry that regulate this differences in order to let the laptop work fine.

I have to admint that I have always wondered how universal PSUs work. Anyone knows?

Cheers!
You seem to be fascinated with v/a/w? Learn what they mean? You seem to be at odds with your own statements?
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post #7 of 19
12/2/09 at 5:01am
Thread Starter 
Quote:
Originally Posted by Ericko View Post
*A PSU wuth 19.5V and less than 4.62A is NOT OK, if your laptop needs the full 4.62A, it will try to get them from the PSU and the PSU will respond dropping the voltage, so at the end you will get less voltage and less current that the one you need
Actually what usually happens in that case in real life is that the PSU gets to hot and burns itself out.

To give you the actual figures the Energy Knight P70W D-D PSU (which is a multi PSU wich uses fuses with a resistor in it to regulate the current but has interchangeable tips, so it doesn't really have to be jerry rigged - my father has just lost the other fuses with different resistors) has at the moment the 20 W fuse/resistor combination, and it's rated at 70 watts with input power from 11-15V, and output dropping from 4.8 to 3 A with fuses/resistors from 15-24V.

The original 220V PSU for the computer is rated at 19V, 3.42 A and 65 watts.

To me those numbers are pretty similar, since the 12V psu should be able to deliver the necessary amps in that area. I may try it only for a few minutes and measure the current from the psu with a multimeter.

And for the record, Ericko: A stable 12V dc-dc psu (and this one's rock solid, it has several hundred hours use and never a problem) will set you back a lot more than $50! Especially here in Norway. I'm guessing you didn't notice that this was a car PSU.
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post #8 of 19
12/2/09 at 6:20am
The only time I use a car adapter is with a converter/generator that gives me 12V (or whatever from the cigarette lighter) to 120VAC brick where I finally hook my notebook ac adapter to it!

cheers ...
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post #9 of 19
12/2/09 at 6:38am
Thread Starter 
Yeah, that's possible when you've got an alternator charging the car battery when you need it. Then you can use the inverter. But that is a problem with my father, because he uses the computer in his wooden boat, where an inverter would eat up the battery he uses for the computer and the lanterns in a few hours. The efficiency is incredibly low when the inverter is converting from 12 to 110/220V and the notebook PSU then converts it back again to the 19V or whatever the computer needs. I would guess that the inverter eats up the battery at least 20 times as fast as a real DC-DC PSU, from my own tests in my car (where I have a dedicated carputer).
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post #10 of 19
12/2/09 at 6:41am
I can understand the battery being eating up; the converter would work perfectly (and making more sense) if the machine (car/boat) is running.

cheers ...
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post #11 of 19
12/2/09 at 6:47am
Thread Starter 
Yeah, I forgot to say that it is a sail boat! That complicates matters a bit. He likes to sail from dawn till around 6-7 P.M. when he's on his longer trips, which means that the computer needs to be able to run at least that for his navigation. Then he sometimes stays at an island or some other remote place without power, so two full days of navigation is at times needed. The Dell PSU can do it without any problems, but not an inverter.
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post #12 of 19
12/2/09 at 7:38am
How about a small generator?

cheers ...
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post #13 of 19
12/2/09 at 7:41am
Thread Starter 
Or maybe a windmill? Much greener and more eco friendly...
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post #14 of 19
12/2/09 at 8:01am
Quote:
Originally Posted by Mastiff View Post
Or maybe a windmill? Much greener and more eco friendly...
That's definitively a thought. Just look at DK, powering the whole Christmas tree in the main square in Kopenhaven with bicycles

cheers ..
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post #15 of 19
12/7/09 at 1:00am
I'm going to go out on a limb here and say it's probably not going to work. Laptops generally ID the power supply they are attached to and if they can't tell what's hooked up they tend to not work properly, if at all. I'd just shell out for a DC to DC PSU that works with your dad's ASUS. After all the $100 or so a DC Power supply costs would be far less than the replacement cost of a laptop.

Also, if battery longevity on his boat is a concern I'm pretty sure there are companies out there that make 12V Photo-voltaic systems for sailboats. You can also jerry-rig a car's alternator to work from wind power. Basically it's a matter of replacing the pulley with a prop and speed control assembly (to prevent over-speeding really). There's a company in Canada that makes them from GM Alternators. In fact most of those commercially available 12V wind generators are designed for use with deep cycle marine batteries.
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post #16 of 19
12/7/09 at 5:01am
Thread Starter 
Sounds interesting, but unfortunately it's a classic sailboat (around WW2), so he won't change it's appearance. And the replacement costs will be zero because it will be covered by the warranty, which is crazy in Norway compared to what you are used to in the US! As long as they can't prove he's been using the wrong PSU the shop can't even protest.
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post #17 of 19
12/7/09 at 10:39pm
Quote:
Originally Posted by Mastiff View Post
And the replacement costs will be zero because it will be covered by the warranty, which is crazy in Norway compared to what you are used to in the US! As long as they can't prove he's been using the wrong PSU the shop can't even protest.
Interesting. I wonder how do they manage to not to go out of business.
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post #18 of 19
12/8/09 at 6:54am
Thread Starter 
Mainly because they all have exactly the same rules, so it does not affect competition. And everything's more expensive in Norway than in countries with weaker consumer protection laws. And we don't have the million dollar lawsuits over hot coffee... That can be a problem in the US, but I don't know if it's that bad in Mexico.
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post #19 of 19
12/8/09 at 9:38pm
Quote:
Originally Posted by Mastiff View Post
Mainly because they all have exactly the same rules, so it does not affect competition. And everything's more expensive in Norway than in countries with weaker consumer protection laws. And we don't have the million dollar lawsuits over hot coffee... That can be a problem in the US, but I don't know if it's that bad in Mexico.
We don't have those silly lawsuits, even the ones that should actually be prosecuted aren't.

Prices are higher than in the US, sometimes they go up to 2x higher. But that is not a problem for me, I live in the border and I buy almost everything in the US. It's cheaper, you have more options and you have way better warranties.

Cheers!
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