USB charging

i see all these laptop "chargers" now with USB ports in them. the simplest of them just a small box to plug into the outlet, with from 1 to 4 charging "slots" on the back. yet my PC (and all PCs before it) are/were power by a lengthy, ROUND wire!

what's the deal, do i have a special USB port just for this purpose, or do i get some sore of USB-to-power cord????

 

I haven't seen a charger that powers the laptop via usb, instead lots of times you can charge cell phones/ipods with usb power. And chargers starting to offer usb ports for that type of charging.

 

I don't think it would even be possible to charge a laptop via USB either. The usb connector is only designed to handle a power of 2.5 watts '500ma at 5v' as of USB 2.0 specification. USB 3.0 has been bumped up to 900ma so around 5 watts, for comparision a laptop can draw easily draw 50watts when charging,

If you notice each laptop has a different size round connector, this is because the more wattage the larger the connector has to be so the plug has enough contact area to handle the current, usb has very thin copper connectors with a small contact area so it's very limited in this respect. They have to use the right size connector by law or the device wouldn't pass safety checks and hence wouldn't be legal to sell anywhere.

As Coleman said they're just for charging usb devices without connecting them to a computer.

 

Hi Cat,

That's not a real USB port. It only supplies 5 VDC to charge devices that are designed to charge from a USB port.

Jim

 

ahhh, very clear thank you! that's what i get for using a cellphone built in 1872....

back to laptops for a sec, how many variants on power cords ARE there? a friend's broke and she asked to borrow mine -- i told her no, they are model-specific, but then i got to thinking there's only so many things to vary in a given configuration: polarity, voltage, maybe amperage. so now i'm thinking maybe there's like 18 basic combos covering the hundreds and hundreds of PCs out there.

are powers cords interchangeable across SOME models? like, are there LISTS on the interweb somewhere segregating models into "type A" "type B" "type C" etc cords?

btw, do all cords have the transformer in the MIDDLE nowadays? what's the deal on that? the early models were at the wall, but i haven't seen that for a decade or more now.

i've never really liked it in the middle coz it sits on DIRTY FLOORS that way, but i guess there's some basic reason for it. just to keep it from covering up/clogging the outlet? or from overheating it?

 

They're too big to fit on a plug socket.

There's loads and every time a new laptop comes out that draws more power or has a different voltage they change the connector, if they use one that's too small it's unsafe, if they use one that's too big it costs too much to manufacture, so there isn't any kind of standard.

The polarity has to be the same, the voltage has to be the same, the wattage or amperage has to be higher than the rating of the laptop so it can handle it, make sure of these things and it will work.

 

so are there LISTS out there? as in "the Dell Xxxx will work in an HP Yyyy; the ASUS Zzzz in a Lenovo Wwww"?

seems to me voltage is always between 4v and 22v or so, right? break that up into .5v increments...throw in x2 for polarity...you're still around 72 basic combos as long as the wattage is up there.

so maybe 18 was low but still way less than the number of laptops. for a given manufacturer, for example, i wouldn't be surprised to hear that every last model uses a variant on 4 or 5 basic configurations.

 

No that I know of, I think they use whatever they choose for each model.

For example I did a laptop repair recently where the power supply was broken, it was 18v 60watt on a toshiba, I had an 18v 60 watt lying around from a toshiba but the connector was about 0.25mm too big so I had to remove the connector from the old laptop and solder it to the power supply.

Saying that there are lists for these cheap generic laptop power supplies where one model will work for another but the lists I've seen in the store I go to only lists the laptops within one brand that would work with the same laptop IIRC,in the store they had about 50 different power supplies that cover most major brands and models but I don't have access to the list I've only glanced at it.

If there is a list of compatible power supplies I'd like a copy.

 

Also, had an old boss, who kept having to have his laptops power jack replaced, like every couple months it would stop charging. Eventually we (me) realized his cheap 3rd party power supply had the same tip, but branched out at a "L" shape, and was causing extra stress on the jack, causing it to break off. Replacement his power brick with a legit one and had no more problems.

 

Hi All,

Colemanguy has a good point. One of my friends let his grand-kids play with the laptop on the floor. The power connector got stepped on twice which broke the input connector.

Jim