Re: Converting mains battery charger for 12v operation

From: Daniel Kelly \(AKA Jack\) (d.kellyNOSPAM_at_NOSPAM.ucl.ac.uk)
Date: 07/27/04 

Date: Tue, 27 Jul 2004 18:50:23 +0100

Hmmm... having looked again at the PCB, I'm not so sure!

Take a look:

http://www.ucl.ac.uk/~ucgadak/charger_components.jpg
http://www.ucl.ac.uk/~ucgadak/charger_merged.jpg
http://www.ucl.ac.uk/~ucgadak/charger_tracks.jpg

I want to put 8.45v onto C22 (it's marked on the last 2 JPGs). There are a
total of 3 transformers. 2 of which have 240v on both sides (i.e. their
coils are symetric). And there's definitely circuitry to produce 320v DC
(D1 is a high voltage rectifier).

Urg. I dunno anymore. Any thoughts?

Thanks,
Jack

"Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in message
news:ce647t$1qe8$1@uns-a.ucl.ac.uk...
> Hiya,
>
> I'm 99.999% sure my charger works in way "A".
>
> All the control circuitry for the LiIon charging is on a little daughter
> board, which is definitely downstream of the 8.45v I measured across the
> smoothing cap.
>
> Thanks,
> Jack
>
>
>
>
> "Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message
> news:zb-dnTGSQPl56JvcRVn-ug@comcast.com...
> > Jack,
> >
> > I want to point out that there are basically two ways the charger can
> work:
> >
> > A. The AC line is stepped down to a low voltage, rectified, and fed to
the
> > charger. The 8.45V is the input to the charger. This is what I am
> assuming.
> >
> > B. The AC is rectified to give 160 -340 VDC, which then goes to a
> switching
> > regulator. The 8.45V is what goes to the battery. If this is the case,
> > forget it.
> >
> > Tam
> > "Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message
> > news:0Y-dne4Ly4wn-5vcRVn-qg@comcast.com...
> > >
> > > "Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in
> > message
> > > news:ce5d6i$1oeu$1@uns-a.ucl.ac.uk...
> > > > Hi Tam,
> > > >
> > > > Yes, I've taken the lid off the battery charger. It turns out the
> > voltage
> > > > across the smoothing capacitor (downstream of the step-down
> transformer
> > > and
> > > > diode rectifier) is 8.45v.
> > > >
> > > > Thanks,
> > > > Jack
> > >
> > > This is the unregulated voltage, right? I can't come up with a reason
> why
> > it
> > > should not work if you run 8 - 9 V from a 3 terminal regulator to this
> > > point. Your rectifier diodes will prevent the transformer from
shorting
> > out
> > > the DC. I assume the actual battery voltage is 6V nominal. I guess
this
> is
> > > what you proposed originally. The thing to watch for is if the thing
> uses
> > > positive ground. Could cause fireworks if any grounded metal on the
> > > camcorder touched grounded metal on the car. Of course, the camcorder
> > > probably has no exposed metal. At any rate I would be sure to include
a
> > > fuse. Measure the DC current when running off AC.
> > >
> > > I think some of us are confused as to what the topology is. Is the
> actual
> > > charger in the camera, in the brick, or do you remove the battery from
> the
> > > camera and connect it to the charger? Any power jack on the camera
> should
> > be
> > > labeled as to what the voltage range is. Either on the camera, or in
the
> > > instruction book. My Ricoh Hi8, for instance, uses a 6V battery. The
> > camera
> > > has a label that states 6 - 7.5VDC. You remove the battery for
charging.
> > >
> > > Let us know how things work out
> > >
> > > Tam
> > >
> > >
> >
> >
>
>

Relevant Pages