"John Laird" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Wed, 22 Dec 2004 13:41:02 GMT, Franklin <(E-Mail Removed)> wrote:
>
>>How does the time to charge a Nokia from a PC's USB port compare to
>>the time taken by an original Nokia charger (eg ACP6 standard charger
>>or ACP8 fast charger)?
>>
>>I can measure 4.9V from the USB charger plug and 6.0V from the ACP8
>>plug but I don't have any info on max current.
>
> USB 1.1 and 2.0 both specify a maximum current of 0.5A on each port. That
> would appear to be similar to the output of my SE fast charger, nearly 50%
> more than my Nokia standard brick, and as I can't find any of the Nokia
> fast
> chargers that should live here, not sure on that, but would guess
> "similar".
I read a great big long article about this, and the answer is not as simple
as this.
When a power drawing device is first plugged in it is only supposed to draw
0.1A (IIRC), but may negotiate up to 0.5A or (1A?) on a direct port; it is
also supposed to drop back, if say external power is removed from a hub.
So your charging cable may do one of three things: -
1. Trickle charge at <=0.1A.
2. Negotiate properly.
3. Cheat and draw as much as it can.
My [dumb, but legit] USB phone charge cable does option 1, so just keeps the
phone on and hardly charges it at all.
Many cheapo devices (like lights) draw far more current than they are
supposed to. This wll probably not hurt too much on a desktop, but may
cause problems in a laptop.
>
> --
> Better to be thought stupid than to speak and confirm it.
>
> Mail john rather than nospam...
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