USB port power

[barry wilkins]

My wife has a Flip Camcorder ,bought it about a year ago ,but she hasnt used it much.
She has been trying to charge it,you do it by pluging in the usb plug into a computer .
First she used her Toshiba Satellite and it did not charge up,then she used a mains usb charger we bought from John Lewis ,still no good.
So we left in my ACER Aspire overnight ,but when we tried it yesterday at a party it failed,flat battery.
My nephew had a mains usb charger and we plugged it in for about a hour ,and that seems to have done the trick.
I know usb ports have a limited ammount of current you can draw from them.
Has anybody had similar problems ?

Barry Wilkins

[Scenic]

Re: USB port power

I've had problems like that with front USB ports on cheap computer cases.
The wiring to those USB ports is too thin for the current. On laptops, it might be limited on purpose.

Regular USB ports are supposed to deliver 5V at max. 500mA (0.5A .. or 2.5W).
Some are capable of delivering more than 500mA (mostly on desktop PCs), some can't even deliver 200mA, which makes them useless for stuff other than USB Keyboards/Mice or USB sticks, which don't need much power.

External Laptop-style optical drives and 2.5" HDDs without an extra PSU are common to cause problems, cause they're right on the edge of that 500mA limit, with some needing far more than that to work.

My brother has a 2.5" 320GB USB HDD which needs about 830mA on startup, and roughly 450mA during normal use. It doesn't work at all on his laptop (fails to spin up .. just clicks), unless he puts it on an USB hub with an external powersupply.
On his desktop PC, it works fine, but only if he plugs it in on the back. Front ports also don't deliver enough current for it to start up (possibly the same too thin wire problem)