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Proper voltage setting for laptop car adapter?

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Last response: in Laptops & Notebooks
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Anonymous
a b D Laptop
January 5, 2005 5:05:34 PM

Archived from groups: comp.sys.laptops (More info?)

I know nothing of electricity except that if you stick your tongue in a live
lamp socket you'll get an instant perm. So, I need some help.

The vice president of the company recently bought a laptop, and with it a
car adapter that the salesman recommended. I have to get these two devices
to work together.

The laptop AC power converter says that its output is 18.5 volts. The car
adapter will output to a range of voltages: 15, 16, 18, 19, 20, 22, 24.

Clearly I need to set it to either 18 or 19, but beyond that I'm stumped.
Will 18 be not enough? Will 19 be too much? Which is the better choice if
I want to avoid damaging the laptop? Should I just chuck this adapter and
buy another that has an output of exactly 18.5? Do these exist?

Any help would be appreciated.


**
Captain Infinity
Anonymous
a b D Laptop
January 5, 2005 5:05:35 PM

Archived from groups: comp.sys.laptops (More info?)

Captain Infinity <Infinity@world.std.com> writes:
> Clearly I need to set it to either 18 or 19, but beyond that I'm stumped.
> Will 18 be not enough? Will 19 be too much? Which is the better choice if
> I want to avoid damaging the laptop? Should I just chuck this adapter and
> buy another that has an output of exactly 18.5? Do these exist?

Do one of two things:

1) Buy a car adapter made by the laptop manufacturer for that laptop,
since some generic one might not have enough capacity or voltage
regulation.

2) Buy a 12 VDC to 120 VAC adapter and plug the laptop's normal AC
adapter into it.
Anonymous
a b D Laptop
January 5, 2005 5:05:35 PM

Archived from groups: comp.sys.laptops (More info?)

Well Bob, looks like u got one of them universal adapter.

Why not get one specifically made for your model? Company is not doing
well? VP of Walmart?

Running the thing on 19v will probably make things run hotter, and
(maybe) produce premature failure of the unit, but unlikely. By that
time, the laptop would have gone obsolete first.

Running the thing on 18v (maybe) will take the batt slightly longer to
charge and the screen (maybe) slightly dimmer (if anybody can notice
it). No premature failure here.
Related resources
Anonymous
a b D Laptop
January 5, 2005 5:20:02 PM

Archived from groups: comp.sys.laptops (More info?)

Salesmen have some the least knowledge of electrical and
most to gain by promoting something wrong. Did that car
adapter claim to have load dump protection. Load dump is a
unique type of surge as defined by both SAE J1455 and ISO
7637-1. Did the salesman even know what load dump is? Can he
cite the numerical spec that says the adaptor meets those load
dump requirements? If not, then walk quickly away. Any
salesman that recommends a car adaptor immediately knows of
load dump and damage it can do to a laptop.

Defined are automotive transients up to 270 volts and energy
up to 50 joules. You tell me if your car adaptor will keep
that out of the computer. It must.

He's a VP. Cost of a new laptop is not a major expense.
Things are disposable. What is your financial situation - a
rhetorical question? What does the laptop manufacturer
provide? Manufacturer is more interested in your laptop life
expectancy.

Captain Infinity wrote:
> I know nothing of electricity except that if you stick your tongue
> in a live lamp socket you'll get an instant perm. So, I need some
> help.
>
> The vice president of the company recently bought a laptop, and
> with it a car adapter that the salesman recommended. I have to
> get these two devices to work together.
>
> The laptop AC power converter says that its output is 18.5 volts.
> The car adapter will output to a range of voltages: 15, 16, 18, 19,
> 20, 22, 24.
>
> Clearly I need to set it to either 18 or 19, but beyond that I'm
> stumped. Will 18 be not enough? Will 19 be too much? Which is the
> better choice if I want to avoid damaging the laptop? Should I just
> chuck this adapter and buy another that has an output of exactly
> 18.5? Do these exist?
>
> Any help would be appreciated.
Anonymous
a b D Laptop
January 5, 2005 11:32:21 PM

Archived from groups: comp.sys.laptops (More info?)

I'd go 18 unless there are problems with the laptop (lockups or
crashes), in which case I'd try 19 volts. 18 volts will let the laptop
run a bit cooler, perhaps. You have at least a 5% tolerance to work
with, so both 18 and 19 volts are well within the tolerance [however,
that does assume that the adapter itself isn't out of tolerance, e.g.
that it doesn't really produce 17 (or lower) when you set it to 18]. In
all liklihood, you actually have a 10% or greater tolerance.

You didn't mention current, but the laptop has a stated current
requirement, and ideally the car adapter should be able to supply that
much current as well.


Captain Infinity wrote:
> I know nothing of electricity except that if you stick your tongue in a live
> lamp socket you'll get an instant perm. So, I need some help.
>
> The vice president of the company recently bought a laptop, and with it a
> car adapter that the salesman recommended. I have to get these two devices
> to work together.
>
> The laptop AC power converter says that its output is 18.5 volts. The car
> adapter will output to a range of voltages: 15, 16, 18, 19, 20, 22, 24.
>
> Clearly I need to set it to either 18 or 19, but beyond that I'm stumped.
> Will 18 be not enough? Will 19 be too much? Which is the better choice if
> I want to avoid damaging the laptop? Should I just chuck this adapter and
> buy another that has an output of exactly 18.5? Do these exist?
>
> Any help would be appreciated.
>
>
> **
> Captain Infinity
>
Anonymous
a b D Laptop
January 5, 2005 11:32:22 PM

Archived from groups: comp.sys.laptops (More info?)

Once Upon A Time,
In article <41DC4FBC.6050509@neo.rr.com>
Barry Watzman wrote:

>Captain Infinity wrote:
>> I know nothing of electricity except that if you stick your tongue in a live
>> lamp socket you'll get an instant perm. So, I need some help.
>>
>> The vice president of the company recently bought a laptop, and with it a
>> car adapter that the salesman recommended. I have to get these two devices
>> to work together.
>>
>> The laptop AC power converter says that its output is 18.5 volts. The car
>> adapter will output to a range of voltages: 15, 16, 18, 19, 20, 22, 24.
>>
>> Clearly I need to set it to either 18 or 19, but beyond that I'm stumped.
>> Will 18 be not enough? Will 19 be too much? Which is the better choice if
>> I want to avoid damaging the laptop? Should I just chuck this adapter and
>> buy another that has an output of exactly 18.5? Do these exist?
>>
>> Any help would be appreciated.

>I'd go 18 unless there are problems with the laptop (lockups or
>crashes), in which case I'd try 19 volts. 18 volts will let the laptop
>run a bit cooler, perhaps. You have at least a 5% tolerance to work
>with, so both 18 and 19 volts are well within the tolerance [however,
>that does assume that the adapter itself isn't out of tolerance, e.g.
>that it doesn't really produce 17 (or lower) when you set it to 18]. In
>all liklihood, you actually have a 10% or greater tolerance.
>
>You didn't mention current, but the laptop has a stated current
>requirement, and ideally the car adapter should be able to supply that
>much current as well.

OK, this is helpful, thank you. I know nothing about current requirements
or how they're determined. Is that Volts, Amps, or Watts? Here are the
specs as printed on the two units:

Power supply (AC adapter)
Input: 100-240V ~ 2.4A 50-60Hz
Output: 18.5V === 4.9A
90W

Car adapter (DC adapter)
Input: DC 11-14V
Output: DC 15/16/18/19/20V 3.5A max
DC 22/24V 2.9A 70W max
Fuse for overload protection: 10 AMP


Sorry, I should have included these specs with my original post.


**
Captain Infinity
Anonymous
a b D Laptop
January 5, 2005 11:32:23 PM

Archived from groups: comp.sys.laptops (More info?)

Captain Infinity wrote:
> Once Upon A Time,
> In article <41DC4FBC.6050509@neo.rr.com>
> Barry Watzman wrote:
>
>> Captain Infinity wrote:
>>> I know nothing of electricity except that if you stick your tongue
>>> in a live lamp socket you'll get an instant perm. So, I need some
>>> help.
>>>
>>> The vice president of the company recently bought a laptop, and
>>> with it a car adapter that the salesman recommended. I have to get
>>> these two devices to work together.
>>>
>>> The laptop AC power converter says that its output is 18.5 volts.
>>> The car adapter will output to a range of voltages: 15, 16, 18, 19,
>>> 20, 22, 24.
>>>
>>> Clearly I need to set it to either 18 or 19, but beyond that I'm
>>> stumped. Will 18 be not enough? Will 19 be too much? Which is the
>>> better choice if I want to avoid damaging the laptop? Should I
>>> just chuck this adapter and buy another that has an output of
>>> exactly 18.5? Do these exist?
>>>
>>> Any help would be appreciated.
>
>> I'd go 18 unless there are problems with the laptop (lockups or
>> crashes), in which case I'd try 19 volts. 18 volts will let the
>> laptop run a bit cooler, perhaps. You have at least a 5% tolerance
>> to work with, so both 18 and 19 volts are well within the tolerance
>> [however, that does assume that the adapter itself isn't out of
>> tolerance, e.g. that it doesn't really produce 17 (or lower) when
>> you set it to 18]. In all liklihood, you actually have a 10% or
>> greater tolerance.
>>
>> You didn't mention current, but the laptop has a stated current
>> requirement, and ideally the car adapter should be able to supply
>> that much current as well.
>
> OK, this is helpful, thank you. I know nothing about current
> requirements or how they're determined. Is that Volts, Amps, or
> Watts? Here are the specs as printed on the two units:
>
> Power supply (AC adapter)
> Input: 100-240V ~ 2.4A 50-60Hz
> Output: 18.5V === 4.9A
> 90W
>
> Car adapter (DC adapter)
> Input: DC 11-14V
> Output: DC 15/16/18/19/20V 3.5A max
> DC 22/24V 2.9A 70W max
> Fuse for overload protection: 10 AMP.

You may have already figured this out based on the info previously posted;
but NO, this one will NOT work! Don't even try it! It may lull you into
thinking it's adequate by working for a while, but based on the above, it's
about 20 watts (or two amps--take your pick) shy of the requirement.
Something's inevitably going to blow.....

{ONE EXCEPTION: it may be adequate for merely CHARGING the battery of the
unit, as long as the laptop is NOT powered up while connected to it...I'd
still say 'no'}

You need one that has the correct voltage within a half a volt or so (not
critical), but one that AT LEAST equals the current (4.9 A[mps]) and/or
power (90W[atts]) requirements. If those two figures are higher on the one
you get...no problem. It may even be an advantage if you later trade that
laptop on a more power hungry one.
>
>
> Sorry, I should have included these specs with my original post.
>
Yeah, if you had I could have told you then...no harm. There are a lot of
'good deals' out there on 70 watt supplies these days...IF you can use them.

jak
>
> **
> Captain Infinity
Anonymous
a b D Laptop
January 5, 2005 11:42:43 PM

Archived from groups: comp.sys.laptops (More info?)

I take issue with the negative comments on the universal adapter.

The input to the laptop from the power adapter is merely the input to a
switch mode switching power supply inside the laptop. That input has
relatively wide tolerance and is well isolated -- it's not used directly
for anything, other than as an input to the internal switcher.

Universal supplies are generally fine as long as they are at least "in
the ballpark" on current capacity. That has become an issue recently,
because some of the newer laptops can require 90 to 140 watts, while
many of the universal power supplies put out only 60 to 75 watts -- at
best. So if you are way off on power capacity, then you do have an
issue in that regards, but otherwise, it should be fine.

[Power (watts) = volts (18 or 19 in your case) multiplied by amps]

[so, a laptop that needs 18.5 volts at 4 amps needs 74 watts]

My qualifications: Degreed engineer, holder of US computer patents, A+
and Network+ certified, have worked as product manager, marketing
manager & engineering manager for PC makers (including laptop makers).


bobb wrote:

> Well Bob, looks like u got one of them universal adapter.
>
> Why not get one specifically made for your model? Company is not doing
> well? VP of Walmart?
>
> Running the thing on 19v will probably make things run hotter, and
> (maybe) produce premature failure of the unit, but unlikely. By that
> time, the laptop would have gone obsolete first.
>
> Running the thing on 18v (maybe) will take the batt slightly longer to
> charge and the screen (maybe) slightly dimmer (if anybody can notice
> it). No premature failure here.
>
!