[Techtalk] [OT] charging USB device without a PC

Conor Daly conor.daly at oceanfree.net
Sun Apr 13 00:56:45 EST 2003

On Sat, Apr 12, 2003 at 01:39:59AM +0100 or so it is rumoured hereabouts, 
Maria Blackmore thought:
> On Fri, 11 Apr 2003, Conor Daly wrote:
> > Badly OT I know but...
> Well .. it's technical ...

And to drag it slightly on topic, on the box it claims to support "Win2k,
ME, XP, Mac OS >=10.1.2 and Linux >=2.4.0".  Just plug in and it's there
as /dev/sda.  Very nice to see support quoted on the box.
> > Uses a lithium battery that charges off the USB port.
> Presumably, you mean a lithium ion battery?

> > I have a 5Vdc charger (from another device) and I'm just wondering if
> > it would be fatal to the USB device to attempt to charge it from that.
> > I can desolder a USB socket from an old mobo and hook that up to the
> > charger which can deliver up to 2.5A.
> That's pretty chunky for 5V, the maximum current draw from a USB
> port is 500 mA, so that should be just fine

It's for a big lump of a personal MP3 CD player that lives in the car
(~150 CDs in a 24CD wallet and > 10 hours of music before I need to change
CD).  It seems to need most of those amps!
> The failure mode of a lithium ion battery that is being
> improperly charged usually involves scattering red hot metal and chemicals
> around the area, so all lithium ion batteries are "smart".

> In theory you should be able to use one of the generic variable voltage
> power supplies with its output set to 4.5V, since the minimum acceptable
> voltage on a USB connection is 4.4V.  You'll just need to make sure that
> whatever supplies it can source 500 mA at least.

What's the max voltage offhand?  

> Have fun :)

OK, did that.  USB socket off an old mobo, power socket off an old 
receiver.  It's now hooked up to the charger with the charging light on. 
<runs off to check> Yup, charging complete, battery not even warm...  I'll
have to run the battery flat and test properly.

Thanks all for all the info.

Conor Daly <conor.daly at oceanfree.net>

Domestic Sysadmin :-)
 12:44am  up 23 days,  6:20,  0 users,  load average: 0.00, 0.00, 0.00
 12:44am  up 23 days,  6:19,  1 user,  load average: 0.17, 0.06, 0.01

More information about the Techtalk mailing list