The Notebook Review forums were hosted by TechTarget, who shut down them down on January 31, 2022. This static read-only archive was pulled by NBR forum users between January 20 and January 31, 2022, in an effort to make sure that the valuable technical information that had been posted on the forums is preserved. For current discussions, many NBR forum users moved over to NotebookTalk.net after the shutdown.
Pretty sure the
CF-AA1653A is the original one for the CF-30, but wanted something to charge the battery a bit quicker. Would either of the other two harm anything if used ??
something like that ... that is the idea though ... except ... that lind unit appears to be only a 12VDC input .
also ... does it have a yellow tip ? if it aint yellow , forget it .
and those "plug-in-the-right-tip" types are about as worthless as a screen door on a submarine .
*someone* must sell the item across the big pond .
I am an electrical engineer who was in product design for many years so I will give you the scoop;
The power supply only needs to provide as much current as the load (laptop) can take. You can go with a higher capacity power supply but you should understand the pro's/ con's;
A higher capacity supply will be slightly less efficient, more power is spent on keeping things idling along under low demand conditions.
But it will probably run cooler as it is not screaming to just keep up.
Also it will probably last longer because of lower temperatures and stresses on the supply.
The extra power capacity is useless; unless you planning on splitting the output to other devices that are not inside of the laptop case. The charging circuitry of the laptop will be the limiting factor, it will just not push more current in to the laptop or battery. It is like buying a Porsche when the only driving you do is the two miles to the grocery store once a week. It may look cool, be great for bragging rights but if a car has karma it is probably sad because it never gets a chance to get out there and blaze down the highway.
there is a "sweet range" for swmps to run in (as well as other devices) .
the technology of switch mode supplies has come along way since the early 80s ...
some of the supplies back then required a minimum load (usually a resistor across one of the outputs) to keep things from grenading ...
some supplies came with a warning against firing up the supply if not hooked into a circuit to provide a load on the supply .
today , these supplies can be very robust ... a 3KW output supply that will fold back smoothly to match a "no load" condition .
the efficiency curve is important to take into consideration in order to keep operational costs down .
another aspect is the outright cost : the cost of a porsche is considerably higher than a mustang shelby (sort of depends on the exact model though) .
the longevity of a swmps hinges on the quality of the electrolytic capacitors ...
heat and high ripple current are the two biggest offenders that contribute to the demise of the electrolytics in a supply .
but this is getting into the area of design/cost as opposed to the parameters that an end user can choose from .
I generally use an 8amp IBM charger for everything except in my truck. It may not charge any faster, but I never have to check to have the proper charger for a specific laptop. The CF52's and some CF31's specify a 7 amp charger.
Here is a question for you two engineers.
What are the issues with using a charger with an output lower than the laptop specifies?
or ... a big cube of ferrite (think really big pot cores without the center) to drop the supply into ...
make the walls about 2" thick .
a really big hash slinging qrm generator ?
the lcd display itself on a monitor ...
yeah , let's shield the computer , use ferrite clippenonnenstoppers but leave that big radiating surface wide open !
i have birdies all over the place ... from the bottom of the am broadcast band (and even below !) on up to 30MHz when the monitor is *on* .
it is just about as bad as a poorly shielded crt monitor .
yep ... another one of my pet peeves .
The voltage should be the same. Raising the voltage "may" increase the charging rate but it is also a great way of releasing the "magic smoke packets" that allow electronic devices to operate.
Current is on demand from the load (the laptop) a device that is off, charging or running will draw varying amounts of current. The goal is to have enough capacity in the supply to meet the peak demands from the load (laptop).
Undersizing a power supply (lower current capacity in Amps) means that the device will charge at a slower rate or in extreme cases, will not charge (or boot) at all.
Oversizing a supply (much higher current capacity in Amps) is not a really bad thing, it just means that the supply may be really lightly loaded by the demands from the laptop. Getting completely ridiculous with current capacity is just wasteful as that big supply has to drawpower just to keep running. But... it will last longer because it never really pushes the limits of what it is capable of.
"But... it will last longer because it never really pushes the limits of what it is capable of."
unlike myself ... uuuggghhh .
tish , i concur with your statements .
i would rather slightly over size in current supply than undershoot the mark ... this is not only preferable but in 99% of cases is required .
if you want to know a real killer of equipment , look no further than over zealous , undereducated bean counters .
hmmm ... if you mean "what is more efficient current or voltage in running a load" ...
then voltage will win out .
...
with higher voltage you can do the same amount of "work" with less current .
the IIR losses are less .
My basic curiosity just wanted to know of any damages caused by using a lets say 3.75 amp charger on a laptop that specs a 7.0 amp charger? Overheat the charger? Laptop problems other than possibly not booting? Blow internal fuses?
I "assume" the battery works as a bit of a buffer until it is totally discharged.
I know many guys here use smaller than specified chargers. I like the IBM's because they are super heavy duty and cheap in comparison to an official Panasonic one. You do need to replace the output cable.
the design of the panasonic comps is such that low current supplies will not affect them in an negative manner .
this is one of the basic marks of well designed circuitry .
it just reaches a point where the unit will shut down when the combination of battery and changer cannot supply the current required to keep things going .
kind of like a dysfunctional relationship where it gets to the point where one person drops their toys , stands up , pulls up their pants and says "i'm outta this sandbox ..." and walks away .
Well, the Panasonic power supplies are not as finicky as the Dell's. Those use a small chip built in the supply that identifies the capabilities of the supply and talks using I2C bus down a third wire inside of the power cord. When a Dell sees an undersize supply it either charges at a lower rate or decides that it will either;
1) Charge but not run the laptop
2) Run but not charge the battery
Panasonic appears to be tolerant of that; They assume that you are not going to be really dumb and put too tiny of a supply on the laptop. This also give a bit of an advantage to third party manufacturers of supplies for vehicular installations, they do not need to "fake-out" the I2C communications to make the laptop happy. I would suspect that Panasonic puts smarts in the laptop to identify an undervoltage condition (caused by a too-small supply being overloaded and the voltage drop being significant). When it sees that then the laptop makes decisions in how to deal with the charging rate or the run state of the machine and accessories.
(BTW, I2C is a very simple serial communications interface and protocol that can communicate bi-directionally with a single wire (really two wires, there is a ground in there too. It has been used on Arundo computers, programming interfaces and charging systems).
I have been unlucky enough to borrow a smaller laptop supply for my work Thinkpad or my Dell. Then you discover what it is like to manage your day off of a limited power budget where only 80% of the flexibility of a laptop is possible due to power rationing.
the IIC arrangement has been around for some time and it works well for what it was designed to do .
if you don't need super fast speeds it can be cost effective in controlling devices .
one of the first places i became aquatinted with them was in one of the highest volume consumer electronic devices : televisions .
sony and philips were among the first to use the technology in order to improve the accuracy of dynamic convergence , color tracking and several other functions that were normally performed by a bunch of potentiometer twisting circuits (as well as those pesky rlc circuits on convergence boards) .
as a side benefit i got to go to phoenix and las vegas twice a year for sony , mitsubishi and panasonic (matsushita and philips twice removed) ... in order to "keep up" on the latest developments .
on the other hand , without a bunch of specialized equipment , it can take a very long time to set up (say) the dynamic convergence and gray scale for a tv with a failed board when you have to start from scratch .
however , a soldering pencil , some *chip quick* and a cup of coffee and bob's yer uncle (and hopefully not yer brother at the same time) . remove the eeprom from the dead/defective board and swap it out for the one on the new board .
this sure speeds up the work by at least putting most of the settings in the ballpark .
yes ... a properly designed swmps will fold back to protect itself if the load exceeds the current supply .
FWIW, my CF30 came with a CF-AA1683A 8 amp charger, and when I went hunting a charger for my car(s) I used that as the reasoning behind looking for an 8 amp LIND charger
the 8A chargers will not harm a '30 or '31 ('29 as well) .
the computers have/use switching regulators in several "sub supplies" ... these are much more efficient than the old brute-force *pass transistor* types (less waste heat) .
switch mode supplies are not like the linear (translates to lots of copper and iron) types .
with linear supplies the rule of thumb is that as the rated current output goes up , so does the standby or idling current .
an example of this would be to take the cover off of a microwave oven , disconnect the B+ rectifier lead and the filament leads ...
measure the idling current of the primary with an clamp on amprobe after hitting the go button .
the price of copper and iron has become high enough , along with the cost per KWH to warrant the changeover to inverter or switch mode supplies .
Problems? See this thread at archive.org.
