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Subject: Re: I've done it : FM Recorder opened :-D
From: Joaquim Carvalho (jdc_at_x64.com)
Date: 2003-02-10


On Mon, 2003-02-10 at 21:17, Andrew Jamieson wrote:
> Hmmmmm ..... I've done a bit of googling, and your right. I stand
> corrected. However, I reserve the right to still think it's kinda wierd,
> and "something I would not do"(tm).
>

Yes, but connecting the batteries in series is not a perfect solution
either because batteries all have different capacities and it is not
possible to completely discharge/charge the larger ones without
reverse-charging/overcharging the smaller.
Joaquim

>
> Andrew Jamieson
>
> ----- Original Message -----
> From: "Joaquim Carvalho" <jdc_at_x64.com>
> To: <rockbox_at_cool.haxx.se>
> Sent: Monday, February 10, 2003 10:04 PM
> Subject: Re: I've done it : FM Recorder opened :-D
>
>
> > Many devices, including the Apple Powerbook Pismo use several (6)
> > LI-Ion batteries in parallel so I don't believe there are any
> > substancial problems with this solution. The Pismo batteries last
> > for 5 hours which is surprisingly good even for a PPC notebook.
> > Joaquim
> >
> > On Mon, 2003-02-10 at 10:43, Andrew Jamieson wrote:
> > > Ive used Li-Ion batteries to power a device that drew ~2A peaks with two
> > > cells in series. With cells in parallel I dont understand how you would
> > > prevent them from draining each other due to slight differences in
> internal
> > > impedance and voltage, without external ciruitry to prevent cross flow
> of
> > > current.
> > >
> > > Which is probably what they have, but I still think its wierd :) Better
> to
> > > connect them in series and then use a step-down to reduce the high side
> > > current draw.
> > >
> > > A
> > >
> > > ----- Original Message -----
> > > From: "Stuart Tedford" <stuart.tedford_at_piresearch.co.uk>
> > > To: <rockbox_at_cool.haxx.se>
> > > Sent: Monday, February 10, 2003 8:36 PM
> > > Subject: RE: I've done it : FM Recorder opened :-D
> > >
> > >
> > > > > -----Original Message-----
> > > > > From: Andrew Jamieson
> > > > >
> > > > > However, it's interesting to see it uses two Li-Ion batts,
> > > > > but it looks like
> > > > > they are connected in parallel ..... _very_ wierd. Very wierd
> indeed.
> > > > >
> > > >
> > > > No, its not that weird. I've got a data sheet for a MAX1684EEE DC-DC
> > > > convertor IC (as used in PDA's etc) that states that a 1.5 Amp output
> > > > requires the use of 2 Li-ion batteries, otherwise you only get 1 Amp.
> It
> > > > must have something to do with the batteries internal resistance - if
> I
> > > > remember rightly from my EE diploma some years ago :-)
> > > >
> > > > Stu.
> > >
> > >
> >
>
>



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